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Messages 1 - 310 of total 310 in this topic
dipper

climber
Topic Author's Original Post - Dec 31, 2009 - 10:15pm PT
I am diggin all the rock talk.

I used to climb with geology students and they would enlighten me as to what I was jamming and and lay-backing off of.

So have at it with this image.

What is going on here?


Shack

Big Wall climber
Reno NV
Dec 31, 2009 - 11:10pm PT
Obviously horizontal stratification of post metasedimentary...
oh, never mind, I have no idea.

Bryan?
The Mr. Ben

Social climber
Boston
Dec 31, 2009 - 11:27pm PT
Could be a calcite deposit. If so, lenticular deposits such as this often occur in marine depositional environments, if that rock is limestone. If not, it could be secondary (i.e., water leaks through cracks in the rocks and precipitates out dissolved calcium). My hunch is #1.
Anastasia

Mountain climber
hanging from a crimp and crying for my mama.
Dec 31, 2009 - 11:33pm PT
I'm guessing...
I think that is an iron deposit on top getting all rusted and quartzite in the middle.
Am I right or did I fail gloriously?
:)AFS



dipper

climber
Topic Author's Reply - Dec 31, 2009 - 11:54pm PT
More data for the armchair rock-hounds

taorock

Trad climber
Okanogan, WA
Dec 31, 2009 - 11:56pm PT
lenticularite in laminated intercoursite?
Ihateplastic

Trad climber
Lake Oswego, Oregon
Jan 1, 2010 - 12:01am PT
uh..huh, huh... you said intercoursite!
taorock

Trad climber
Okanogan, WA
Jan 1, 2010 - 12:10am PT
I did - whoops. Old geo joke - another fcuking rock.

Must really be quartz in metasediments.
dipper

climber
Topic Author's Reply - Jan 1, 2010 - 02:01am PT
Some context for those interested


Mungeclimber

Trad climber
sorry, just posting out loud.
Jan 1, 2010 - 02:11am PT
I have no idea what it is.

The real question is how does it boulder?
Curt

Boulder climber
Gilbert, AZ
Jan 1, 2010 - 02:12am PT
Looks like petrified wood.

Curt
LuckyPink

climber
the last bivy
Jan 1, 2010 - 02:14am PT
haha.. just as I thought

"choss pile"
dipper

climber
Topic Author's Reply - Jan 1, 2010 - 02:14am PT
In general, it is as stable as cheap styrofoam. The stuff in the first 2 shots is pretty stable though.
Mighty Hiker

climber
Vancouver, B.C.
Jan 1, 2010 - 02:17am PT
http://supertopo.com/climbers-forum/1018638/What_IS_it_about_choss
dipper

climber
Topic Author's Reply - Jan 1, 2010 - 02:44am PT
Even more context here

Bill Mc Kirgan

Trad climber
Cedar Rapids, Iowa
Jan 1, 2010 - 12:42pm PT
big a** chert nodule ?
cintune

climber
the Moon and Antarctica
Jan 1, 2010 - 02:26pm PT
taorock got it, at least from the looks of it: massive "bull" quartz in lenses and irregular layers, originally deposited deep down in some kind of silt that meta'd to schist.
At least that's what it looks like.
Happy New Year, rockhounds.
Mighty Hiker

climber
Vancouver, B.C.
Jan 1, 2010 - 02:31pm PT
I think I can see the face of Sir Francis Drake in that formation...

Point Reyes has some interesting geology.
Jaybro

Social climber
Wolf City, Wyoming
Jan 1, 2010 - 04:51pm PT
The steinmen trinity?
Minerals

Social climber
The Deli
Jan 1, 2010 - 05:45pm PT
I deleted my bad joke…


Quartzite or quartz vein? There IS granite nearby…

Depositional lens or tectonic lens?

That ain’t Franciscan… And it’s moving!


Geology of Point Reyes:

http://www.sfsu.edu/~geog/bholzman/ptreyes/introgeo.htm



More geo quizzes, please!!! :)


(Edit: Damn link......)


kpinwalla2

Social climber
WA
Jan 1, 2010 - 05:50pm PT
It's a boudin!
cintune

climber
the Moon and Antarctica
Jan 1, 2010 - 11:54pm PT
Maybe it started out as chert and then got baked. If that stuff is even schist; could be just some weird folded mud beds or such.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 2, 2010 - 12:56am PT
At first I thought it looked like Franciscan Chert, but on that side of the San Andreas Fault, your in the Salinian Block not Franciscan.

The photo you posted from the Pt Reyes area looks like younger Neogene shallow marine rocks, likely Purisima or Monterey Fm equivalent.

Looks like some type of nodule, perhaps a phosphate? or dolomite nodule in bedded Monterey Chert.
dipper

climber
Topic Author's Reply - Jan 2, 2010 - 01:27am PT
I used to date a woman that said that about my turbidites....


Sorry, the chocolate, red wine, white wine, mussels, crab, halibut, smoked trout and all the other yummy stuff I just ate are mixing.

Strange brew indeed.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 2, 2010 - 01:36am PT
looks like some kind of biogenic sediment...my guess is a dolomite concretion in bedded chert in the Monterey Fm

I agree BASE104...too large for a nodule...more like a concretion

e.g. check out the photo on this website...
http://www.cnsm.csulb.edu/departments/geology/research/miocenemontereyformation.shtml
Minerals

Social climber
The Deli
Jan 2, 2010 - 01:59pm PT
Tradster, did you see the Lee Vining Canyon stuff in the Yosemite thread?


OK, how about another quiz, for armchairs only (for now). This one is too easy for you geo guys. Not in Yosemite…

What’s going on here?



tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 2, 2010 - 02:58pm PT
Minerals: I just checked the Yosemite Documentary thread and posted on it. I'm thinking about this photo and will post up my '2 cents' later.
Minerals

Social climber
The Deli
Jan 2, 2010 - 03:32pm PT
Right on. That thread disappeared for a couple of days and I wasn’t sure if you saw what I posted, in response to your question.
Jaybro

Social climber
Wolf City, Wyoming
Jan 2, 2010 - 06:39pm PT
You hard rock guys crack me up....
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 2, 2010 - 08:09pm PT
That's an interesting rock. It's difficult to see the matrix or the sedimentary texture. The rock is obviously stratified and bi-modal, so I'm thinking volcanic or sedimentary origin. The individual layers look like they are only a few centimeters thick. The large clasts look granitic but not sure...if granitic then it's probably sedimentary with granitic provenance. The clasts are not sharp and angular so I wouldn't call it a breccia...they're somewhat rounded so they've undergone some transport. I don't see any obvious upward fining or coarsening in the layering but it looks matrix supported and it's interesting how the finer grained layering is deformed around the large clasts, perhaps during burial or metamorphism. Looks like a metamorphosed debris flow or conglomerate, perhaps a distal alluvial or submarine fan. On the other hand it could be predominately volaniclastic. In which case it could be a pyroclastic rock that has undergone some metamorophism...so a metavolcanic rock.

That's my 2 cents.

Jaybro

Social climber
Wolf City, Wyoming
Jan 2, 2010 - 08:54pm PT
Okay, this one is a giveaway!

cintune

climber
the Moon and Antarctica
Jan 2, 2010 - 09:11pm PT
Whoa. The Elder Sign.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 2, 2010 - 09:32pm PT
What do you make of the joint pattern in this Aplite dike near the summit of Mt Whitney?
dipper

climber
Topic Author's Reply - Jan 3, 2010 - 12:03am PT
Thanks all for the tips on the Point Reyes coastal meta-ice cream.

Nice rock pics.

Here is another nice one I spied in the Kern River headwaters area a few years back.

It was a little too heavy so I left it in place. Need to go back and visit it if I can.

Jaybro

Social climber
Wolf City, Wyoming
Jan 3, 2010 - 12:38am PT
Whitney was a Cubist?
Minerals

Social climber
The Deli
Jan 3, 2010 - 12:47am PT
Oooooh… Back to granite!

Tradster, that is a way cool photo! Wild pattern! Aplite dikes are commonly fractured when the host granitic rock is not – this is due to the difference in competence between the coarse-grained granite(?) and the fine-grained aplite – the materials behave differently. As far as the two sets of fractures at right angles to each other, I’m not sure why exactly this pattern forms. I’d like to take a class on fracture mechanics. Cleo and others can probably explain this stuff a lot better than I can.

I did see your “pretty” outcrop before it disappeared… reminded me of “Snoopy” on the way to the Black Rock.


Nice mirror image, Dipper! Looks like a chunk of well-foliated granodiorite(?) that hosts a stretched mafic enclave that hybridized with the granitic host by “ingestion” of small feldspar crystals from the host (white dots - xenocrysts). Foliation probably formed during magmatic flow, as the enclave was stretched. Both rock types are cut by younger aplite/pegmatite dikes (white bands) that may offset the enclave slightly (can’t tell). Or something like that…
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 3, 2010 - 03:17am PT
I pulled the pretty face on the granite boulder in the Alabama Hills...much to silly for this serious thread. Feast your eyes on these lovely glacier polished feldspar phenocrysts in Cathedral Peak Granodiorite. If I recall correctly, this photo was taken along the cascade behind Pywiack.

Cathedral Peak Granodiorite, Sierra Nevada Batholith, California: A Big, Mushy, Magma System?
Burgess, S. D.; Miller, J. S.; Matzel, J. P.

The broad geochemical and isotopic data are consistent with bulk fractionation in the Cathedral Peak Granodiorite. However, the geochemical spatial variation (especially trace elements) and field evidence suggest that fractionation was highly disorganized and involved mixing and remobilization of crystal mush as it solidified, possibly triggered by new inputs of isotopically uniform magma (i.e., recharge from the magma source).


Minerals

Social climber
The Deli
Jan 3, 2010 - 01:51pm PT
Oh, man, Tradster… You are going to open a can of worms with that one!

Seth Burgess is/was a student at San Jose State – I met him briefly at a poster session at a GSA meeting in San Jose in 2005. I have spent a day or two in the field with Jonathan Miller, a professor from San Jose State.

An abstract, similar to what you found?

http://adsabs.harvard.edu//abs/2006AGUFM.V11A0551B


A Big, Mushy, Magma System? Ummmmmm...

Bulk fractionation at the final emplacement level is so 1979………

I don’t want to get into this in this thread… way too complicated and it should be reserved for a Tuolumne-specific geo thread… someday.


For now, those are some pretty orthoclase megacrysts!



More geo quizzes!!!
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 3, 2010 - 01:59pm PT
Opening worm cans...isn't that what the Taco Stand is all about? Hey I understand..no problem. I'm trying to learn from you guys. I've spent a lot of time in Tuolumne climbing on the domes during the last 30 years but never delved too deeply into the geology. I've always been fascinated by the rocks that make up the roof pendants. I'll wait for your Tuolumne Intrusive series thread before posting anymore photos/abstracts like that. BTW, that was an AGU 2006 Fall mtg abstract.

I'm not a hard rocker...the only hard rock work experience I've had is a summer job with a mining company back in 1978 working on a scheelite-bearing Skarn deposit outside of Mina, NV (Gunmetal mine). It was mined for Tungsten during WWII for armor-piercing munitions. Mostly I described core and did some surface and subsurface mapping. Many cool contact metamorphic minerals, pyroxenes, epidote, etc...I had no idea what many of the minerals were. I would use a UV lamp on the cores & outcrops at night to estimate the scheelite content. One of the lessons I learned that summer was that working in a mine is very dangerous. I wish I had photos from that time period but I don't.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 4, 2010 - 08:19pm PT
Fans of Geoporn, feast your eyes on this optical televiewer image of a borehole wall. The image is generated with a wireline digital camera. It is oriented in geographical coordinates and is essentially the borehole wall displayed as a 2D image (i.e., North is at both ends of the image).


For scale, the image is ~1 meter of the borehole
Minerals

Social climber
The Deli
Jan 5, 2010 - 01:11am PT
Yeah, we like to open a lot of cans around here, but this is one that I would like to wait on. There is some rather heated controversy going on these days with regard to how plutons form, complete with blatant attacks. I just don’t want to get myself in trouble. But don’t worry, there isn’t much that I’d rather discuss than the geology of Tuolumne Meadows, especially when there are folks who are interested and will listen!

I didn’t see that you added a second paragraph to your above post at first.


“…working on a scheelite-bearing Skarn deposit outside of Mina, NV (Gunmetal mine).”

NO WAY!!! Now you’re talkin’!!! I LOVE that area! It’s my county! Mineral County! Mina, Luning, and Soda Springs Valley… all of that area east of Hawthorne – it’s so cool out there. Need to get back soon! Spent a bunch of nights at the old Dunham Mill site (below Gunmetal mine) last winter and checked out the Desert Scheelite mine and Good Hope mine. I didn’t make it all the way up the hill to the Gunmetal mine – need one of my dirt bikes for that!

You gotta love skarns… and all of the cool minerals that form when magma intrudes limestone (Luning formation in this case) and cooks the piss out of it! There’s more garnet than a sandpaper manufacturer knows what to do with! We have so many skarn deposits here in Nevada, and no shortage of old mines that exploited them. I love it!


From Geology and Mineral Deposits of Mineral County, Nevada, by Donald C. Ross, 1961, p. 74:

“The Gunmetal mine near the east base of the Pilot Mountains and some of the mines of the Santa Fe district (T. 8 N., R. 35 E.) have had production, chiefly during and after WWII. These properties are developed in scheelite-bearing tactite bodies which formed from limestone along or near contacts with granitic rock. Most are low-grade deposits, but locally they contain ore that averages 1 percent or more of WO3.”

(tactite = older term for skarn, for those who don’t know)

Scheelite:
http://en.wikipedia.org/wiki/Scheelite



WHAT…? Mines are dangerous???













Chrysocolla (hydrated copper silicate), Desert Scheelite mine

Chrysocolla:
http://en.wikipedia.org/wiki/Chrysocolla


The view east: Mine dump and Kibby Flat, from Desert Scheelite mine
Look familiar, Tradster?



Hey Tradster, that is a cool image! So, the image covers 360° of the borehole walls? Minor faults? What do you see in that image?

Jaybro

Social climber
Wolf City, Wyoming
Jan 5, 2010 - 01:38am PT
You guys is lax on yer Forams! would ostracods, or conodonts be better?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 5, 2010 - 02:07am PT
The view east: Mine dump and Kibby Flat, from Desert Scheelite mine
Look familiar, Tradster?

Minerals: looks familiar in that your photo is typical of basin & range terrain with alluvial fans & playa lake but it was so long ago I couldn't say if I've been to that particular area. What I recall is that when we were UV lampin' the outcrops near the Gunmetal mine at night you could see the lights of Tonopah off in the distance to the southeast. The mine was an hour commute on gravel roads east of Mina where we were staying. Here's the location of the Gunmetal mine on a Google map.


I was working with a mining geologist from Missoula, Montana who had done 2 tours of duty as a marine in Nam. He was intense...heavy drinker and chain smoker. He had his vices & I had mine. I respected him for serving even though I opposed the war. Anyway the adit to the mine was located right on a contact between granite and limestone. The contact metamorphic zone or skarn consisted of a solid layer of garnets several feet thick that contained scheelite & molybdenite. I wish I had photos from back then but I didn't even own a camera. It was a summer job while I was in grad school at UC Davis.

Have you ever been in the Pine Creek mine?

Hey Tradster, that is a cool image! So, the image covers 360° of the borehole walls? Minor faults? What do you see in that image?

Yes the image covers 360 degrees. It shows relatively flat lying interbedded siltstone and claystone offset by a steep NW-dipping fault with minor offset. The steep fault forms a sinusoid pattern on the image and the bottom of the sinusoid points in the direction of the dip azimuth (NW). If it was a vertical fault and the borheole was vertical, the pattern would be 2 parallel lines. If you know the borehole diameter(6")you can estimate the dip magnitude using simple trigonometry (i.e. the vertical distance between the top & bottom of the sinusoid (~30")form 1 leg of a right triangle and the borehole diameter forms the other leg). It appears to be a high angle (arctan of 30/6 = 79 degrees)reverse fault because the beds are lower in the foot wall than the hanging wall...correct?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 5, 2010 - 12:56pm PT
Jaybro: bring it on...how about some diatoms, radiolarians
Jaybro

Social climber
Wolf City, Wyoming
Jan 5, 2010 - 02:36pm PT
Let me check the pelagic, and get back to you...
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 5, 2010 - 02:40pm PT
While you're down there check the biogenic ooze
brotherbbock

Trad climber
Alta Loma, CA
Jan 5, 2010 - 03:10pm PT
It is obviosly Schmegmatite.
sgarlick

climber
North Conway, NH
Jan 5, 2010 - 03:38pm PT
Wow, great thread and amazing photos!
Jaybro

Social climber
Wolf City, Wyoming
Jan 5, 2010 - 04:16pm PT
I favor the globigerinal ooze, part...
guyman

Trad climber
Moorpark, CA.
Jan 5, 2010 - 04:23pm PT
Cool can o worms opened up here.

Dipper, The second photo looks like the stone at New Jack City, a popular destination for supertopians...... :>)

And Minerals, please keep up with the info, I really like studying the stone.

Have you seen the "Sand Stone Intrusion" on Power Dome at Courtwright Res?

Just wondering.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 5, 2010 - 11:33pm PT
here are some examples of biogenic ooze that was deformed during subduction
subduction is friction between the sheets that can lead to orogeny
Mighty Hiker

climber
Vancouver, B.C.
Jan 6, 2010 - 12:22am PT
Yaaaaaay! More geoporn. And not a creationist or politician to be seen.

I worked in geological exploration a few summers, so can sort of follow it.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 6, 2010 - 12:46am PT
Yes the Pine Creek mine (also a skarn deposit) is located off HWY 395 near Bishop. When I visited the mine we rode for a couple of miles in an ore cart until there was ~8,000 ft of rock above us.

There's only 3 things in a mine...rock, steel, & flesh...flesh always loses out.

Yes, the folded Franciscan chert in the photos above is most likely soft sediment deformation.
50

climber
Stumptown
Jan 6, 2010 - 12:56am PT
Tradster - Great photos of the ooze. Looks like the California coast. Possibly the Son-o-ma Beach area north of San Francisco?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 6, 2010 - 01:08am PT
Exactly right 50...the annotations on those photos are, of course, intended to be humorous.

As you know Franciscan knockers make good sea stacks.

jfailing

Trad climber
A trailer park in the Sierras
Jan 6, 2010 - 01:32am PT
Sweet thread - anyone ever scoped the Poleta Formation? I mapped part of this sucker for my senior exit requirement at UCSC. It is a complicated maze of multi-generational folding and faulting - chaotic enough to tear your hair out...


Tradster - I love that quote, though I've always known it simply as "They say that subduction leads to orogeny..." Also, where is the entrance to the Pine Creek mine? I climb up there all the time - it's interesting to note the series of paved sidewalk terrace things from the old mining days. I think you can see them on google earth.
dipper

climber
Topic Author's Reply - Jan 6, 2010 - 01:45am PT
Thanks for all the info on the rocks.

For the fools amongst us, like myself, that want to learn it, can you mark your made up stuff as humorous?, so I know what to attempt to commit to memory and what to have a chuckle over.

Here are some dikes. Is the goo that filled the cracks aplite? I saw that term mentioned above.
Is that similar to plagioclase feldspar? Forgive my spelling and thanks for all the insights.



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BASE104

climber
An Oil Field
Jan 6, 2010 - 01:51am PT
God, if you want to hear some horror storys of difficult geology, I got em. They all involve wasting a very large amount of money. But we always blame the engineers.

And there are places that are so chopped up that they make those folds in the picture above downright friendly.

Those shiny things in the lava tubes look like casts of something smooth...like a gas.

You see that stuff all the time in turbidite outcrops. Not vesicles, but flute marks. Tells you which way the flow direction came from.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 6, 2010 - 01:55am PT
jfailing - the Pine Creek mine is an enormous mine that can only be accessed by permission and escort from the mining company that operates it. Not sure if it's still active. When I was there in the late-1970s on an economic geology field trip from UC Davis I think Union Carbide operated the mine.

Many schools hold their field camp in the Poleta Folds area...the geology there is so complicated it challenges anyone who tries to make sense of the chaos.

I did my field camp in the northern foothills of the Avawatz Mts, south of Death Valley National Monument. We mapped a deformed sequence of Quaternary deposits that formed the flanks of a fault bounded anticlinal structure with a pre-Cambrian granite-gneiss core. This is a tectonically active area with vertically dipping Quaternary playa lake and evaporite deposits situated at the convergence of the Death Valley and Garlock fault zones.

Vertically-dipping Quaternary alluvial fan deposits

Quaternary playa lake & evaporites in the foreground and light colored, pre-Cambrian granite-gneiss at about the middle of the photo. The view is looking north into Death Valley from the foothills of the Avawatz Mts.
jfailing

Trad climber
A trailer park in the Sierras
Jan 6, 2010 - 01:55am PT
BASE - so what's the most structurally complex area you've dealt with? Expensive eh? Sounds like oil... I did some mudlogging in Elk Hills near Bako - not too structurally difficult, but cool stratigraphy!
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 6, 2010 - 02:11am PT
Here are some anticlinal structures from the Big Horn & Powder River Basins Wyoming
jfailing

Trad climber
A trailer park in the Sierras
Jan 6, 2010 - 02:12am PT
Wow, you weren't kidding about the horror stories... you've got me stumped! I can imagine that a 12 pack might help in interpreting that sort of feature...

What kind of rock is it? The only thing that comes to mind would be some sort of compression cave-in or something close to its deposition or deformation - if it's related to a reservoir, this may be tangible?
dipper

climber
Topic Author's Reply - Jan 6, 2010 - 02:16am PT
TT,

Very cool images.

Whenever I flew (not much any more) I always spent the bulk of my time with my nose pressed to the window to see just that sort of feature. I do believe I have flown over the images you posted, long ago.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 6, 2010 - 02:17am PT
BASE that structure in the image you posted looks like extensional faulting on the crest of a dome...a collapsed dome.

When we flew over the Powder River-Big Horn Basins I was stunned.
BASE104

climber
An Oil Field
Jan 6, 2010 - 02:30am PT
My buddy shows me this map. We are all wicked drunk, but instead of chasing tail, the geologists pull maps out.

He asks us what we think it is (and this was a really subtle feature, but you could see it). We all strike out and he says, "Astrobleme." If only we knew the economic significance of this.

Nobody drilled into it because the deep zones in this place don't produce for fifty miles in any direction. It was known about for ages. It is near a tiny town in northern oklahoma, flat as a pancake wheat country, named Ames. It was dubbed the "Ames Hole" by geologists long ago.

Well, a deeper well was drilled to the cambro/ordovician on the rim, on a little structural closure, and found the rocks totally fractured..which they aren't anywhere else, and the zone covers three states, one being Texas. The rock was just a mess. It is pretty plain jane everywhere else.

Then it caught on, people drilled around the rim and made discoveries that were exciting, but not that remarkable. Then a company drilled into the rebound feature in the middle and found nothing but shocked Quartz in what should have been a granite basement. It looked like glass. Shocked Quartz was confirmed, a zillion articles were written about it, and the rebound feature made millions of barrels of oil. The impact feature was self-sourced, meaning that the organic source rock (normally the Woodford Shale in Oklahoma) was from Ordovician shale that filled the crater. You can type the hydrocarbons back to the source rock with a little geochemistry. I think that this one is about ten miles across. I can look it up, or you can google "Ames Hole" or "Ames Astrobleme."

There are some of these in sedimentary basins in western Canada that are huge producers as well.

Ya gotta wonder how many of these things are out there buried and/or deformed. Lots.

edit: All sedimentary limestones other than in the rebound feature, which supposedly was devoid of feldspars and other granitic jazz. Just quartz.
BASE104

climber
An Oil Field
Jan 6, 2010 - 02:32am PT
And that Bighorn Basin stuff. Those are called Sheepherder Anticlines, because the sheepherders could see them they were so obvious.
Jaybro

Social climber
Wolf City, Wyoming
Jan 6, 2010 - 02:39am PT
If you look in the farright corner of one of Tradster's photos, i believe you can see Frank waving from the top of the Second pitch of Mr Clean, on Deto!

Can a geomorphologist or a structural geologist ever be bored?
BASE104

climber
An Oil Field
Jan 6, 2010 - 02:45am PT

Oh. I always yack too much. The feature is an Ordovician Astrobleme (impact crater). On the northern shelf of the Anadarko Basin. It hit a super thick limestone section. Covered with about 8000 feet of younger sediments. Read my long winded jazz above for details.
Darwin

Trad climber
Seattle, WA
Jan 6, 2010 - 03:01am PT
As an amateur geologist (very amateur!, but with a bit of P-chem background) , I love this thread. For a "real (climbing) world" spin on it check out:

http://supertopo.com/Trip-Report/10506/Pursuit_of_Bluebonnet_Tower_and_the_Lost_Crystal_Cave_Sawtooths_Idaho

OK I admit, for the geology obsessed, the trip report meanders, but it gets there.


Darwin
jfailing

Trad climber
A trailer park in the Sierras
Jan 6, 2010 - 04:59am PT
BASE - that is WICKED! My first thought when I looked at that photo was "that looks like a crater, but... nawww" That's a pretty amazing feature... at 8000' too! Great story - blows my mind.
BASE104

climber
An Oil Field
Jan 6, 2010 - 05:13am PT
Yeah, 450 million year old sucker. Punched through the seds into granite and the central rebound feature was nothing but quartz. The geologist who wrote this up said it looked exactly like broken glass. Which is not like normal quartz grains or crystals look like under a scope.

Whole thing was covered up and buried. I bet there are a zillion of these things if we could just peel off the surface and get a clean look at the stable craton surface.

You can't see it well in that image, but if you look straight down at the maps of the thing it is perfectly round.
dipper

climber
Topic Author's Reply - Jan 6, 2010 - 08:59pm PT
Some more gravel to gander at





1






b (special Toulumne edition for Minerals)






gamma
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 6, 2010 - 11:43pm PT
Jaybro: is this the photo you're referring to? This is a mega sink hole in Florida where phosphate mine tailings leached Uranium into the ground water. Local climbers took advantage of the steep wall and turned it into an outdoor climbing gym until Bechtel grouted it up.
Jaybro

Social climber
Wolf City, Wyoming
Jan 6, 2010 - 11:47pm PT
Nice!
Fritz

Trad climber
Hagerman, ID
Jan 7, 2010 - 12:11am PT
Re. my Sawtooth story mentioned earlier. I am not a geologist, but this thread is fun to lurk on: since two of my old outdoor buddies were geologists. Geology is always of interest.

Plenty of Sawtooth crystals came out of pegmatites, but most of the crystals came out of miarolitic cavities(gas pockets) in pink leucoratic granite. In some areas these cavities are everywhere, but are very small (like pockets in rhyolite at Topez Mountain, Utah). Some are larger, a very few: much larger.

There are some huge Sawtooth smoky quartz crystals on display in the University of Idaho Geology Dept. building.

Certain areas of the range have spessartine garnet as well.

Cool stuff dudes!


tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 7, 2010 - 12:22am PT
cool sample Fritz...what's the mineral with the metallic luster?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 7, 2010 - 02:13am PT
Fritz: just read your Sawtooth - Quartz crystal cave TR...great story. Thanks for posting it.
BASE104

climber
An Oil Field
Jan 7, 2010 - 02:26am PT
I wish that all of you hard rock people had access to the toys of the oil business..mainly 3D seismic data. It can show incredible features now, and new attribute analysis is coming out every day. Downside is that it is uber pricey. You can now see things that are unreal.

Do you guys do any paleomag work? That is really cheap and interesting.

This site has a ton of publications.

You can see basement lineaments and make rose diagrams, see deeply buried incised valleys, all sorts of stuff. And it is all deep underground.

There is a paper in there on igneous intrusives in a sed basin in Mexico that most of you can enjoy.

Scroll down through the equations and gobbledy gook and look at the pretty pictures.

http://geology.ou.edu/aaspi/publications.php
Minerals

Social climber
The Deli
Jan 7, 2010 - 02:39am PT
Will try to catch up on all of the cool new stuff that you guys have recently posted soon… This thread is way fun!

A few photos from today, in cold Northern Nevada:



Tertiary ash fall tuff (terminology???), containing pumice fragments (light-colored) and other volcanic fragments


Well-jointed Tertiary vesicular basalt and what looks to be a fault breccia to the left of the hammer


Closer view of breccia zone


Deformed Tertiary sedimentary rock


Geologic Time Scale:

http://www.geosociety.org/science/timescale/timescl.pdf





OK Jaybro… Here’s a photo that I’ve been meaning to post for ya for a while. Completely silicified bone fragments, found in loose float derived from Tertiary sedimentary rock. These are obviously mammal fossils, given that they are in Nevada. What’s up with them mammals from millions of years ago? Death by volcanic eruption (ash…)?



tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 7, 2010 - 02:48am PT
BASE: I did my MS Thesis in paleomag. Magnetostratigraphy of the Late Neogene Purisima Formation, Santa Cruz County, CA. Back in the days using a Schonstedt Spinner Magnetometer & AF demagnetization. Did all my number crunching on a main frame computer. I would carry a shoebox full of punch cards containing a Fortran program and my data that I would submit to be run overnight.

http://adsabs.harvard.edu/abs/1986E&PSL..79..431M

BASE104

climber
An Oil Field
Jan 7, 2010 - 02:59am PT
Well, it has come a long way. Powerful computers are getting very cheap. A 3D seismic volume has an unreal amount of numbers in it.

The big cost is acquisition.

The grabens in Nevada have had petroleum geologists salivating for ages. There is this one tiny field in Railroad Valley that had one well that for a while was the best onshore oil well in the continental US. The geology is horribly complicated, and people have been drilling dry holes all around that thing for ages.

The really cool stuff comes from attributes (just something that you can yank out of the straight data).

That link above is to a whole division at OU that does nothing but attribute analysis and development. They can see incredible things.

You see all of those igneous joint patterns? Well, you can see them in the igneous basement below sedimentary basins, and they control a lot of the structural geology.

The coolest one is called coherence. It is too much to just steal a picture, so here is a link to a good paper. Just look at the pictures and read the captions. It is uber cool.

http://www.cseg.ca/events/luncheons/2009/10oct/20091014-chopra.cfm
dipper

climber
Topic Author's Reply - Jan 7, 2010 - 02:59am PT
More oddities from the west base of the Inyo Mountains. Any ideas what caused this?




A






zwei (detail of above shot)







3
BASE104

climber
An Oil Field
Jan 7, 2010 - 03:06am PT
Cool abstract, TT! I was wondering if the hard rock guys are doing more of this. It is cheap and can tell you tons. I would go so far to say that if you are doing surface geology without it, you are kind of in the stone age. One of my professors was way into paleo mag. He had this device that filled a whole room. Inside of it, the earth's magnetic field was canceled out. By now, I bet you can go to Wal-Mart and buy the same device that will fit on your desk..but i dunno.

The biology department put all kinds of migrating things inside it like salamanders and what not. So they could show that they were using the earth's magnetic field to migrate with. Then they would disect the snot out of them, run stuff through a mass spec and find magnetite of some sort in the brain.

And of course the usual stuff. During this time period, this location was at such and such latitude as continents drifted around.

You can do a lot with paleomag. You can bang on rocks and work their spatial and temporal data to death, but a simple plug of rock will tell you a lot.

Doing geology without geophysics is really limiting yourself. With seismic, you see things that have different densities..and therefore velocities. I would love to see what it would look like if it was shot in a totally igneous area.
Fritz

Trad climber
Hagerman, ID
Jan 7, 2010 - 12:12pm PT
tuolumne_tradster: Glad you enjoyed my Sawtooths story. Re your question:
what's the mineral with the metallic luster?

The spessartine in the photo shows two different colors: the light orange most of us associate with spessartine, and that darker color. I don't think it is camera-angle. The crystals were fairly small, maybe 8mm at the largest. Per this closeup photo: the two colors just seem to merge.

I took that photo on a 2006 trip into the west side of the Sawooths. I have never seen garnet in the east side of the range. Apparently some places have a lot of spessartine, but it was new to me.

Keep those "geology talk" posts coming guys!

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 7, 2010 - 02:17pm PT
sometimes referred to as a melange
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 7, 2010 - 02:36pm PT
coast range ophiolite??

franky

climber
Davis, CA
Jan 7, 2010 - 02:47pm PT

This is a coal strip mine in PA. They excavated an entire coal bed from an anticline, leaving the clay below the coal perfectly exposed. That big feature in the middle is essentially the same bedding plane throughout. One of the sweetest outcrops in the world no doubt.


By the way, I didn't see anyone mention that the first photo was probably a good example of boudinage.
dipper

climber
Topic Author's Reply - Jan 7, 2010 - 03:38pm PT
DMT,

Those shards that look as if from a chocolate cake were way slick. Would have made for great screeing. Yet, they were so pretty and fragile, I mostly stayed off them.

Here are 3 more postcards from a rock-scape. These are from Center Basin, where the JMT used to go before Forester Pass was blasted into existence.




1






2







3
Fritz

Trad climber
Hagerman, ID
Jan 8, 2010 - 12:10am PT
bump for this thread over the other crap on ST tonight.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 8, 2010 - 12:46am PT
back to the Franciscan Complex...

Blue schist knocker at Goat Rock beach, near Jenner CA
more glaucophane-schist facies metagrewacke...this stuff was buried deep (10s of kiliometers) in a subduction zone before it made its way back up to the surface
Metagreywacke lenses in a sheared argillite matrix
Hidden cove north of Jenner where the above photo was taken
Highly sheared serpentine in a fault zone...like pinching a pumpkin seed between your fingers
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 8, 2010 - 12:57am PT
Minerals: awesome photos from Nevada...especially the pyroclastic rocks and the deformed sedimentary rocks.

BASE104: those horizontal slices from your 3D seismic volume show incredible channel detail

Fritz: thanks for the zoom on the garnets
Spider Savage

Mountain climber
SoCal
Jan 8, 2010 - 01:55am PT
BASE, What do you know about oil exploration under the Columbia basalts? Anything? (Since you seem to be in that field.)

Anyone else?

I've always been fascinated with those. A thousand feet and more of basalt.
BASE104

climber
An Oil Field
Jan 8, 2010 - 05:16am PT
I dunno about the basalts in Columbia that you are talking about, but I do know that there are some sills in Mexico that have been imaged.

The problem you get into is that the densities (gram/CC) generally relates to velocity of the waves, so if the thickness varies, it creates problems. The thing with seismic is that you tie it in with the actual rocks that are drilled through. You can pull an Acoustic Velocity log and then model velocities in the area much better.

This is kind of the same bag of worms that the subsalt play in the gulf of mexico had to deal with. It took a while to model it and figure out, but now the subsalt data is incredible, even while the salt thickness varies hugely above it, with a wildly different velocity.

There is a basin in eastern Oregon..Harney, I think. It is ripe but covered with volcanics. It is also in a really sensitive wetlands area, so nobody messes with it as far as I know.

There are actually quite a few igneous oil reservoirs around. I was at a talk several months ago when the seismic guru started throwing up all of these shots of igneous fields in the seismic data. One was an actual volcanic cone. If you are in a sedimentary basin that has a good source rock, anything porous and permeable becomes a potential reservoir rock.

I am really jealous of the cali boys having ophiolites. I would love to get a free field trip the next time I am out there. I studied them and all that in school, but I have never laid eyes on one.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 8, 2010 - 11:44am PT
BASE104: here's some info on the Cali ophiolites

Models for origin and emplacement of Jurassic ophiolites of northern California
Auteur(s) / Author(s)
INGERSOLL Raymond V. ;

Four Jurassic ophiolite complexes in northern California have crystallization ages of 170-160 Ma; the Coast Range (including Great Valley) ophiolite is oldest (170-165 Ma), the Smartville ophiolite, intermediate (164-160Ma), and the Josephine ophiolite, youngest (162 Ma). The Smartville ophiolite was obducted during the Sierran phase of the Nevadan orogeny (162-155 Ma), and the Josephine ophiolite was obducted during the Klamath phase of the Nevadan orogeny (153-150 Ma). The Great Valley ophiolite was not highly deformed during the Nevadan orogeny and became oceanic basement for the post-Nevadan forearc basin. Three conflicting models for origin of the Coast Range (including Great Valley) ophiolite have been proposed: (1) Formation by intra-arc and backarc spreading related to an east-facing intraoceanic arc, which collided with a west-facing continental-margin arc during the Nevadan orogeny (Sierran phase). (2) Formation by open-ocean seafloor spreading and incorporation into the continental margin during trench initiation outboard of an existing continental-margin trench. (3) Formation by forearc oblique rifting along the continental margin, followed by partial closure. Lithospheric rifting is favored where there is either thick continental crust or thin mantle lithosphere because continental crust is weaker than oceanic crust and both are weaker than mantle lithosphere. Favorable sites for rifting are extant rifts, intra-arc settings, suture belts, and areas where mantle lithosphere has been delaminated from overlying crust. Upon cessation of magmatism related to rifting or subduction, mantle lithosphere rapidly strengthens, so that by 20 m.y., lithosphere strongly resists extensional stresses. Forearcs cool and strengthen even faster because of refrigeration by subducted slabs. Mature forearcs are strong and unlikely to yield to stresses, especially when weaker intra-arc and backarc settings are nearby. Trench initiation is favored by (1) the presence of a preexisting lithospheric boundary, (2) the presence of thin oceanic lithosphere, (3) attempted subduction of buoyant crust, and (4) plate reorganization. Trench initiation in intact oceanic lithosphere older than 20 m.y. is implausible. The following facts render models for Jurassic trench initiation (model 2) or rifting (model 3) in forearc settings implausible: (1) Subduction began along the California margin in the Triassic, so that forearc lithosphere was considerably older than 20 m.y. by the Late Jurassic. (2) The Triassic-Jurassic magmatic arc related to this earlier subduction zone died in eastern California at the same time that the Jurassic-Cretaceous magmatic arc was initiated in the westernmost Sierra Nevada. (3) The colliding buoyant crust that forced this plate reorganization is found in the Sierran foothills. The most plausible model for formation of the Great Valley, Smartville, and Josephine ophiolites is by lithospheric rifting within and/or behind magmatic arcs. The Great Valley and Smartville ophiolites formed behind an east-facing intraoceanic arc. The west-facing continental-margin forearc of California was partially subducted beneath the east-facing intraoceanic arc, and this attempted subduction of buoyant crust resulted in the Sierran phase of the Nevadan orogeny, during which the Great Valley and Smartville ophiolites were obducted. North of this suture zone, no collision occurred, and the continental-margin arc expanded westward, resulting in intra-arc and/or backarc rifting to form the Josephine ophiolite. The Josephine ophiolite was then obducted over its arc during the Klamath phase of the Nevadan orogeny, as the Klamath trench propagated southward to trap the Great Valley ophiolite in the post-Nevadan forearc.
Minerals

Social climber
The Deli
Jan 8, 2010 - 06:10pm PT
OK… gotta catch up a bunch here…


Back to the photo of the metaconglomerate that I posted a few pages back (post #29)… Nice description, Tradster! This outcrop is on the east side of Sonora Pass, before the bottom of the grade. The reason why I like this photo is because it is a good example of how different materials (rock types) behave under deformation. Yes, the large clasts are granitic and are much “stronger” than the other non-granitic clasts and the matrix; this causes the foliation to “wrap around” the granitic clasts. Don’t know the exact geologic unit of this rock, but it’s neat…



Trdaster, nice Google image of the Gunmetal mine area! Google Earth is so cool, and what a fantastic resource for geologists, not to mention desert rats who want to explore. My caption for the view from the Desert Scheelite mine should have read southeast and not east – that view is towards Tonopah.

“The contact metamorphic zone or skarn consisted of a solid layer of garnets several feet thick that contained scheelite & molybdenite.”

Now I am going to have to go up there… maybe find some molybdenite… MoS2… neat stuff!

http://en.wikipedia.org/wiki/Molybdenite


Haven’t been into the Pine Creek mine but have hiked past it. Someone talked about a tour through the mine, somewhere back in the Supertopo pages…

“It appears to be a high angle (arctan of 30/6 = 79 degrees)reverse fault because the beds are lower in the foot wall than the hanging wall...correct?”

Sounds right to me.



“Have you seen the "Sand Stone Intrusion" on Power Dome at Courtwright Res?”

Guyman, no I haven’t. Got a photo or a link? The stuff at Courtwright looks really cool, from the photos that I’ve seen. Would like to check the place out at some point, for sure.



Wes, I recognize a couple of your photos from a previous post. Are those deformed aplite/pegmatite dikelets in a metavolcanic rock or is that a migmatite? Tahoe area, did you say?



Cool metacherts with neat structure, Tradster.



Jfailing, where did you map the Poleta? Looks like somewhere in the desert. I think there are bits of Poleta, caught up in the granites in the southern Sierra, as metamorphic roof pendants. I’ve seen a little out in Esmeralda County, NV, but not enough to remember any details. Saw more of the Wyman Fm and lots and lots of granitic rock.


Got more to type…
Minerals

Social climber
The Deli
Jan 8, 2010 - 07:58pm PT
From post #63:
“Here are some dikes. Is the goo that filled the cracks aplite? I saw that term mentioned above. Is that similar to plagioclase feldspar?”

Nice photos of dikes, Dipper! I like the rock texture in your first photo – looks like porphyritic granodiorite with orthoclase (feldspar) and hornblende or biotite phenocrysts.

Porphyry (rock type) and porphyritic texture:

http://en.wikipedia.org/wiki/Porphyritic


Here’s some info on dikes, from a previous ST thread with a bunch of info on granites:

http://www.supertopo.com/climbing/thread.php?topic_id=731799&msg=744514#msg744514

Here’s an explanation of granitic rock types from earlier in the same thread:

http://www.supertopo.com/climbing/thread.php?topic_id=731799&msg=732325#msg732325


Your 4th photo is of a series of joints (fractures) in granitic rock – these would not be considered dikes.




Tradster, those are cool photos from the Avawatz! Yeah, I think it’s safe to say that if you have vertically-dipping Quaternary alluvial fan deposits, you are in a tectonically “active” area.

Killer Wyoming photos! That stuff just screams the word “geology”!!! Very nice!



BASE104, interesting bit on the Ames Hole. Like Jfailing, when I first saw your graphic image, I thought it looked like an impact crater but figured that it must be some weird structural deal. Neat!

http://search.datapages.com/data/doi/10.1306/522B34E3-1727-11D7-8645000102C1865D



Dipper, thanks for the photo of the chunk of Cathedral Peak granodiorite with a bunch of orthoclase megacrysts! The question is, how do all of those megacrysts get packed together so tightly if they form entirely in a magmatic state? In many cases, simple crystal accumulation is mechanically impossible and cannot explain some of the very-tightly packed “rafts” of megacrysts seen in outcrop. But, I am going to open my bottle of beer instead of a can o’ bait!

Is “gamma” a Cyclops with a mafic enclave for an eye?



BASE104, thanks for the link to the seismic articles! I saved the one on igneous stuff in Mexico and will look over the list of articles in more detail. Also saved the article on subsurface joints.



Dipper, the float in your photos from the Inyo Mountains looks like a pile of chopsticks! My guess is that whatever the rock type (metased?), the chopsticks form because of at least two dominant cleavage angles in the rock, which when exploited by physical weathering, produce the slender rock fragments. So basically, the chopsticks form because of structural weaknesses in the rock.

Cleavage (the geology kind…):

http://en.wikipedia.org/wiki/Cleavage_(geology);


(Cut and paste screwy link again…)
Minerals

Social climber
The Deli
Jan 8, 2010 - 09:11pm PT
As far as the two different colors in the garnet that Fritz posted a photo of… I’m wondering if the darker colored garnet is of a slightly different composition, like almandine. Spessartine, almadine, and pyrope (all garnets) form a solid solution series.

Spessartine:

http://en.wikipedia.org/wiki/Spessartine


Solid solution series:

http://en.wikipedia.org/wiki/Solid_solution



Dipper, the first two photos in your above post have a light “X” pattern that is mirrored between the two blocks. The lighter-colored lines are due to minor chemical alteration of the primary igneous minerals in the granitic rock from hydrothermal fluid flow along joints and small fractures. The plagioclase feldspar appears “bleached” because calcium has been leached from the mineral, shifting its composition more towards a sodium-rich plagioclase, which is lighter in color. Epidote and sometimes chlorite are common secondary minerals that are found in altered zones in granitic rock.


Feldspar:

http://en.wikipedia.org/wiki/Feldspar


Epidote:

http://en.wikipedia.org/wiki/Epidote

(This is the pistachio-green colored mineral that is quite commonly seen in metamorphic rocks and sometimes fills joints as a secondary mineral in some granitic rocks.)


Chlorite:

http://en.wikipedia.org/wiki/Chlorite_group


Getting addicted to Wiki…



Neat Franciscan photos, Tradster!



Hey Anders… You asked about glaucophane? It’s the primary mineral that makes up blueschist, a high-pressure, low-temperature metamorphic rock that is diagnostic of a subduction zone environment. I wrote a 12+ minute song (Blueschist – The Metamorphic Song) back in the early 90’s and used the chemical formula of glaucophane for the time signature in one section of the song – one measure of this section turned out to be in 42/8 time, but it still sounded cool. Glaucophane – Na2(Mg,Fe)3Al2Si8O22(OH)2


Glaucophane:

http://en.wikipedia.org/wiki/Glaucophane



I need to scan some photos of Turtle Rock, my favorite blueschist knocker of all time…
dipper

climber
Topic Author's Reply - Jan 8, 2010 - 09:17pm PT
Minerals,

Many thanks for taking the time to educate. I missed those prior links and have scanned them, but will go back and do them slow roast style for better retention (me hopes).

Man, you know rocks. That chunk o' chickenheads may/may not have once sat in the upper Budd Creek area.

Cyclops came from roadside campsite in Owens Valley somewhere long ago.

I have a chunk of Epidote, if weather and time permits tomorrow, I will post up smore of my collection of treasures.

Your explanations are most appreciated.

-Dipper, the geo-dilletante (Cinclus dilletantus phenocrysti)
Minerals

Social climber
The Deli
Jan 9, 2010 - 01:53am PT
Glad that this stuff is helping you out, Dipper! It’s fun to post and is a good chance for me to brush up on some things, as well as learn more about new things. I enjoy teaching people about the geology that I have learned! What else ya got?



Hey, a question for the extrusive folks out there…

In post #86, I’m not sure of the origin of the breccia zone in volcanic rock in the photos that I posted. I have looked at this outcrop many times over the years, and not knowing too much about the extrusive stuff, have wondered if this breccia zone is of volcanic origin or is tectonic. What do you guys think?




OK… a reach for a granite guy, but still my home turf………….


Stewart Valley Fossils, Mineral County, NV:

http://gsa.confex.com/gsa/2002CD/finalprogram/abstract_35258.htm


http://researcharchive.calacademy.org/research/entomology/Entomology_Resources/fossils/index2.htm



A sign in need of replacement…



Is the “cracking” of the sign due to Basin and Range extension or Walker Lane transtension?



Where’s Obama’s stimulation when you need it??? What’s with all of the pseudo en echelon fracturing and chemical alteration…? :)



Miocene seds… complete with a little cross-bedding and mini fossils



Fresh-water mini crustaceans from BITD, but not too far back



Jaybro, am I starting to speak your language?

How ‘bout this?

http://skywalker.cochise.edu/wellerr/fssl-inv-links/list.htm
Minerals

Social climber
The Deli
Jan 10, 2010 - 12:52am PT
Central Nevada:


Limestone



Tertiary volcanics
Jaybro

Social climber
Wolf City, Wyoming
Jan 10, 2010 - 12:56am PT
Hoh yeah, Bryan, now we're talkin'!
Minerals

Social climber
The Deli
Jan 10, 2010 - 01:04am PT
Cool, Jaybro!
Minerals

Social climber
The Deli
Jan 10, 2010 - 01:05am PT
A simple quiz…


What’s this and when?









Location
Minerals

Social climber
The Deli
Jan 10, 2010 - 01:15am PT
And a related subject…















Fritz

Trad climber
Hagerman, ID
Jan 10, 2010 - 01:28am PT
Minerals: I will jump on this one since "I seen it."
It is a "big" earthquake scarp (fault) line S. of Winnemucca. I can't remember the date---but 1950’s??

It is very similar to the scarp line near Mt. Borah in Idaho from the 7.8 earthquake in the early 1980’s. A women out hunting was actually on the fault line for that one and got to fall back as her turf stayed more or less even and the land next to her ripped up 12 feet.

Re. my photos and assertions that the garnet in the Sawtooths is spessartine: I am quoting my geologist betters. I own several U of Idaho publications that deal with Sawtooth geology and none mention any garnet other than spessartine.

However, as you know----“there is always something new to see.”
Minerals

Social climber
The Deli
Jan 10, 2010 - 01:59am PT
Right on, Fritz! You got it! Yeah, that Borah Peak scarp is cool too! Got photos of it here somewhere.

The above photos are from north of the Dixie Valley and Fairview Peak faults systems - 1954 rupture.

http://www.bssaonline.org/cgi/content/abstract/86/3/761

http://www.seismo.unr.edu/ftp/pub/louie/dixie/



Well, it sounds like your sample is all spessartine. Do you think the change in color is from a trace element of sorts, like the uranium in your quartz crystal? Or just a different color of the mineral? Interesting that there is no mention of any other varieties of garnet in the Sawtooths.
Spider Savage

Mountain climber
SoCal
Jan 10, 2010 - 02:00am PT
BASE. Thanks for the answer. The Columbia Basalts are described in this article:
http://en.wikipedia.org/wiki/Columbia_River_Basalt_Group

Fritz. You know any fun stuff about these? I presume you went to UofI. I have roots there.
dipper

climber
Topic Author's Reply - Jan 10, 2010 - 02:27am PT
Some granite



Mt. Tyndall on the skyline










Minerals

Social climber
The Deli
Jan 10, 2010 - 02:55am PT
Silicified fault breccia




What is the dull-grey mineral?

Fritz

Trad climber
Hagerman, ID
Jan 10, 2010 - 01:47pm PT
Minerals: Re. my spessartine garnet photos from the Sawtooths, I have been quoting from "Idaho Minerals" by Lanny Ream. He seems to have his details down quite well. However, this morning I went digging thru old publications and find that the most detailed: "Reconnaissance Geology of the Sawtooth Range," only says garnets.

So----since the photo was taken in an area that is climber's terrain, maybe it does show a transition from spessartine to almadine. Then again, most spessartine we see as mineral specimens is that nice light orange color. You can see dark colors in spessartine at the minedat.org website. http://www.mindat.org/photosearch.php?cform_is_valid=1&frm_id=mls&minname=spessartine®ion=all&text=&otype=0&stype=0&phototype=M&mtype=0&sort=&submit_mls=Search&phototypeo=M&go=1&cf_mls_page=2

Spider Savage: Yeh, I have a Forestry degree from U of I. I was never too enthused about lava flows. The "channeled scablands" in E. Washington, caused by "glacial lake Missoula," were pretty cool to look at.

I bumped into a geologist friend that works for Idaho Geological Survey a couple years back. He was in this area mapping volcanic flows. We invited him to dinner and he talked for hours about local volcanos and flows. From our back yard he could name the main flow that makes cliffs near our "ranchette." He had mapped it to a volcano that doesn't look like much, that is 20 miles away. It kinda made that basalt stuff a little more interesting to me.

However! Speaking of garnets! I have warmed up to skarns during the last few years. I found some cool garnets in one this summer. It is on the south edge of the 7 Devils range in Idaho and is a inactive copper-mining area. In this case a few big chunks of limestone were floated and metamorphized by igneous intrusions.

There are two types of garnet in the area: andradite and grossular. Unfortunately, I can't be sure which is which? There is also lots of epidote and is some cases the garnets may have been altered to epidote. All very confusing, but fun to look at.



Jaybro

Social climber
Wolf City, Wyoming
Jan 10, 2010 - 01:52pm PT

cross post
Minerals

Social climber
The Deli
Jan 10, 2010 - 07:22pm PT
Jaybro – Ha! Nice eyeball in the grass…



Hey, Fritz… Really nice photos of the garnet! Those are great! Your first photo shows the “diamond-shaped” faces of a garnet crystal. And I see what you mean about the different colors of spessartine, based on your link. I need to go get my textbooks out of storage to be able to discuss this in much more detail. There has got to be a reason for the difference in color in garnet and I’m still thinking that is has to do with composition. From a pocket guide to rocks and minerals, grossular: “…cinnamon-brown to orange when containing iron (hessonite variety) and magnificent emerald-green with chromium (known commercially as tsavorite).”

The darker garnet in your first photo is probably andradite, like you say, and maybe the orange-colored garnet in the other photos is hessonite??? I need my textbooks.


As far as epidote goes, I see the green (epidote) in your photos but think that all of the crystals that are garnet-shaped are garnet – just different colored. I’ve never seen epidote that has replaced garnet. A mineral that is chemically altered to another mineral but still retains its original crystal shape is referred to as a pseudomorph.


Pseudomorph:

http://en.wikipedia.org/wiki/Pseudomorph


Here’s some more info on garnets, but it doesn’t make up for a mineralogy text…

Garnet:

http://en.wikipedia.org/wiki/Garnet



Here’s one from last Wednesday, at a skarn deposit in Northern Nevada that was mined for copper (chalcopyrite).


Calcite (white), epidote (green), and garnet (brown – andradite or grossular)
Photo by Kait

dipper

climber
Topic Author's Reply - Jan 10, 2010 - 07:35pm PT
A few more images to marvel at. These are on the road out to Battery Spencer above the Golden Gate Bridge.













Minerals

Social climber
The Deli
Jan 10, 2010 - 07:46pm PT
Chevron folds in metachert! Nice, Dipper!
Minerals

Social climber
The Deli
Jan 10, 2010 - 10:50pm PT
What is the green mineral?




Any guesses on the dull-grey mineral yet?

Minerals

Social climber
The Deli
Jan 10, 2010 - 10:52pm PT


http://earthscope.org/

http://pboweb.unavco.org/


Jaybro

Social climber
Wolf City, Wyoming
Jan 10, 2010 - 10:55pm PT
Serpentine on it's way to asbestos?
Minerals

Social climber
The Deli
Jan 10, 2010 - 11:47pm PT
Hint: It’s in Nevada and can be of economic interest.
Minerals

Social climber
The Deli
Jan 10, 2010 - 11:48pm PT
More Tertiary seds
Photo by Kait



Megacrysts...

...and enclaves



Granite



Metamorphic rock



Squish

Fritz

Trad climber
Hagerman, ID
Jan 11, 2010 - 12:24am PT
Minerals: Re your quiz questions. The grey stuff doesn't have that galena look to it, and otherwise I can't guess.

For the green: obviously a copper mineral, and I'll go with the obvious --- Malachite.

On your most recent post, last photo, of course I have to comment: Gneiss picture!
kaitb

climber
Jan 11, 2010 - 12:44am PT
Minerals: Okay boys....I think I got a good educated guess as to what the "green" mineral is. I could be kinda cheating considering I got a few tips from being out in the desert this past week with Bryan looking at geology. But here it goes: Chrysocolla?
kaitb

climber
Jan 11, 2010 - 12:54am PT
But the more I look at the image - the green mineral is brighter than the normal turquoise color for chrysocolla - so it just may be malachite. Chrysocolla is a hydrated copper silicate and malachite is a copper carbonate - so both are minerals associated with copper ore bodies.
Jaybro

Social climber
Wolf City, Wyoming
Jan 11, 2010 - 12:57am PT
one of those slickensides, artifacts?

I've seen it in the field...
Srbphoto

Trad climber
Kennewick wa
Jan 11, 2010 - 12:58am PT
Looks a lot like the ribboned chert at Glen Park in SF.


The rock at Battery Spencer is the first place I went when I bought my first climbing shoes (Fires) in 1982.
Minerals

Social climber
The Deli
Jan 11, 2010 - 01:02am PT
Fritz, you are correct on all three. Nice work!

The galena has been exposed at the surface in a mine dump and has lost its Metallica luster but the cubic habit is still obvious, giving us the clue. There is also a bit of sphalerite in there as well – it’s a sulfide deposit.

Right on, Kait!

Yup, malachite filling fractures in either sandstone of the Jurassic Dunlap formation, or limestone of the Triassic Luning formation (according to the Mineral County geologic map)… I forget exactly. There is also a bit of blue chrysocolla in there as well.

The last two outcrops are located along the JMT, Sierra Nevada.


Galena:

http://en.wikipedia.org/wiki/Galena


Sphalerite:

http://en.wikipedia.org/wiki/Sphalerite


Malachite:

http://en.wikipedia.org/wiki/Malachite

apogee

climber
Jan 11, 2010 - 01:22am PT
Can someone provide a layperson/geo-lurker explanation of the formation of epidote?
Minerals

Social climber
The Deli
Jan 13, 2010 - 04:51pm PT
Basically, epidote forms under certain metamorphic conditions with the presence of hydrothermal fluids and chemical/temperature/pressure conditions that favor epidote instead of the higher-temperature primary minerals that the rock was originally composed of. Primary minerals (plagioclase feldspar, etc.) are chemically “hydrated” and altered to form epidote.


From Manual of Mineralogy, 20th ed., 1985:

“Epidote forms under conditions of regional metamorphism of the epidote-amphibolite facies. Characteristic associations of actinolite-albite-epidote-chlorite occur in the upper part of the greenschist facies. Epidote forms also during retrograde metamorphism and forms as a reaction product of plagioclase, pyroxene, and amphibole. Epidote is common in metamorphosed limestones with calcium-rich garnets, diopside, vesuvianite, and calcite. Epidotization is a low-temperature metasomatism and is found in veins and joint fillings in some granitic rocks.”


More info on epidote:

http://www.answers.com/topic/epidote


Hydrothermal alteration:

http://en.wikipedia.org/wiki/Hydrothermal


Metasomatism (a type of metamorphism):

http://en.wikipedia.org/wiki/Metasomatism


Skarn:

http://en.wikipedia.org/wiki/Skarn

dipper

climber
Topic Author's Reply - Jan 13, 2010 - 06:37pm PT
A few more samples from my collection of ballast.




What I am told is epidote







Epidote other side






From inside the crater west of 395 at Deadman Summit







Crater sample 2







Little Colorado abalone pounder






Big Sur coast (rock's name is Lono, as in Curse of, H.S.T)





Are these agates? (From same location as image in first post of this thread







Great Western Divide (glacial polish all of side you see)






Matterhorn (Calif. version) (the long dark lightning bolt thingie)
Minerals

Social climber
The Deli
Jan 13, 2010 - 08:34pm PT
Fritz’s garnet photos inspired me to try a few photos of some of my samples. I grabbed these two yesterday, because they were at the top of the monstrous mound of rock that is in my storage unit. These aren’t great photos, but they are the best that I could do with my current 4-megapixel hand-me-down camera. I’ll have to grab some more samples at some point. OK, a couple more mineral quizzes…



The orange-brown mineral is garnet (grossular or andradite). What is the white mineral?





This sample contains a bunch of garnet with nice, diamond-shaped crystal faces. The white minerals are quartz and calcite. What is the black mineral?






Minerals

Social climber
The Deli
Jan 13, 2010 - 09:01pm PT
Nice samples, Dipper!

Yeah, looks like epidote on a fracture/fault surface in your first two photos. You can see slickensides (parallel lines) and maybe even a slight mineral lineation on the green surfaces. Looks like some pink K-feldspar… a chunk of granite?

Is the second “crater” sample all one piece? Looks cool, like it should be a proud pillar to support a personal treasure. Or maybe just a place to put a beer, provided you set it down properly…

Lono is a cool rock. Some sort of conglomerate?

Those pebbles look like agate or milky quartz.

Nice chunk of foliated granite/granodiorite with aplite dikes.
Paco

climber
Montana
Jan 13, 2010 - 09:21pm PT
It looks to me like foliated metamorphic rock: The white band must be quartzite- but nobody ever called me a geologist.
Fritz

Trad climber
Hagerman, ID
Jan 13, 2010 - 10:14pm PT
Dipper: I am so glad you have continued this thread!
Since I have a “rock hound” background, I will take the agate question. However, anything I say may be corrected by Minerals.

Agate falls into the Chalcedony family of silica minerals. http://en.wikipedia.org/wiki/Chalcedony

However, the “rock hound” definition is: Agate is translucent quartz with a milky texture, or is colored, or shows banding. A piece that is obviously quartz that doesn’t fit this definition is further divided into:
A. Milky Quartz (or the old-timer name: “bull quartz.”)
B. Jasper: has the shinny and hard quartz look, but is colored and opaque.

Another test for quartz is a fracture test. Quartz minerals always have a glass-type (conchoidal) fracture that leaves a very sharp edge with smooth shell-like curves.

Of course all rockhounds define agates still more.
Yah have “Keepers or Perfects.”
Then there are the “leaverites.” (Leave it right there).
And finally the sex stones:
“That’s just another forking rock!”

So-----to finally answer your agate question. I agree with Minerals: the two on the right are agates. The other two are probably water-polished milky quartz and are “leaverites”


Fritz

Trad climber
Hagerman, ID
Jan 13, 2010 - 10:25pm PT
Minerals: Great of you to dig out and post up more garnets.

Re your question on the white crystals. Without looking at a book, I thought "is there such a thing as white Staurolite?"

However with a quick look at a book to check my #2 guess: I see that Kyanite does occur in white and Staurolite does not.

Kyanite is my guess and I'm sticking to it.

Re. the small grey metalic looking stuff. Gun to my head---I would be forced to guess some kind of copper mineral. I really don't have a clue.

I will return the difficult metalic mineral question to you soon!
Minerals

Social climber
The Deli
Jan 13, 2010 - 10:45pm PT
Fritz, nice job with the quartz description! Sounds good to me. But I am still learning here too, and have to read to brush up on some of the details in order to post. Got a few textbooks here and will read up on garnets some more.

I wish the other guys would post up again. Too much surface geology? Hmmmm… BASE and Tradster, where are you guys? Probably busy with real things…

Re. My last mineral quiz. White mineral… The type of garnet is a hint…

And the second mineral is black, not metallic. This mineral is fairly common.

It’s tough to really see rock/mineral samples on a computer screen, compared to holding the sample in your hand.
Fritz

Trad climber
Hagerman, ID
Jan 14, 2010 - 04:16pm PT
Minerals: My final try at IDing your white mineral crystals is: Wollastonite. Not much of that in Idaho. I had to cheat and research skarn minerals.

Here are some easy to ID specimens from a copper mine in an altered limestone skarn.



OK: Then we have the 3M (mystery metalic mineral) special I am not sure of. I have an old USGS report on this location. Only metalic minerals mentioned are iron minerals, molybdenite,and copper minerals.


This mineral cleaned up to a silvery metallic look as in the first photo. It formed thin layers in that green mineral in photo 1, and edge-on almost had a mica-book look to it. In the wild it was much darker as per the last photo.

I ended up putting a mild solution of chlorine bleach on one of the cleaned up specimens that grew mold, and it darkened almost to a black color.
I have a guess, but I really don’t know what it is.



Fritz

Trad climber
Hagerman, ID
Jan 14, 2010 - 05:40pm PT
Weschrist: Yes I am. It started dark, and I cleaned the specimen in a vinegar solution, then soap and water: and the mineral got shinny.

I made the mistake of putting a couple that were not completely dry in a sealed container and they molded. When I killed the mold with a very dilute bleach solution: the shinny got dark again--maybe darker than when I found them.
Fritz

Trad climber
Hagerman, ID
Jan 14, 2010 - 07:29pm PT
weschrist: Nope not Fritz from SLC. I can't help you with hardness and streak, other than "it ain't real soft and it ain't real hard".

I will agree the shinny photo looks like galena. It is not galena.

I am 99% sure it fits into one of the categories I cited: iron minerals, molybdenite, or copper minerals.

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 15, 2010 - 02:48am PT
Great stuff everyone. Just got back from Colorado, so here are some geo photos from the trip.

Barringer Meteorite Crater near Winslow, Arizona taken on the flight from Phoenix to Durango. One of the best preserved meteorite craters on the planet. Estimated to be 50,000 years old. It is 1,200 meters in diameter & 170 meters deep.

http://www.meteorcrater.com/



This photo also taken on this flight. Not sure what canyon this is but it has some cool desert towers. Anyone recognize it?



This photo was taken near Telluride. I believe these are Tertiary volcanic rocks of the San Juan Formation but I'm not sure.


This photo was taken from the Ames Hydroelectric Power Station outside Telluride where the famous Ames Ice Hose climb is located. Not sure what formation it is but thought the structure looks interesting.

Minerals

Social climber
The Deli
Jan 16, 2010 - 01:39pm PT
Fritz, you are correct. The white mineral is wollastonite.


Wollastonite:

http://en.wikipedia.org/wiki/Wollastonite


More nice photos, Fritz.

The first looks like epidote, with a little bit of garnet.
The second looks like garnet and chrysocolla.
The third one looks like epidote, chlorite, calcite (shiny cleavage surface), and your metallic mystery mineral.


Does this look like your metallic mystery mineral?




Any guesses on the jet-black mineral yet? Here’s another photo of the mineral:




More epidote, with chlorite (darker green) on the left side of the photo; the white is quartz (May Lake area, Yosemite):


Minerals

Social climber
The Deli
Jan 16, 2010 - 01:46pm PT
Tradster, you are back! Cool.

Nice photos! The one of Meteor Crater is neat – nice view and nice light! The sinuous drainage pattern in the background gives it a little bit of scale.

Neat colors/layering in the Tertiary volcanics.

Yeah, some neat structure in your last photo, and some interesting rock – maybe even to a climber!
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 02:37pm PT
Minerals: my guess is that the black mineral is hornblende
Minerals

Social climber
The Deli
Jan 16, 2010 - 02:54pm PT
Close, Tradster.
Jaybro

Social climber
Wolf City, Wyoming
Jan 16, 2010 - 02:58pm PT
Texas Canyon? There are unnamed towers there.
Minerals

Social climber
The Deli
Jan 16, 2010 - 03:41pm PT
Here’s some hornblende in Half Dome granodiorite from Tuolumne. Notice the 60° and 120° amphibole cleavage angles seen in cross-section of the mineral. Hornblende usually appears as black rectangles. Notice the white dots (feldspar) within the hornblende – when a mineral contains smaller crystals of another mineral, the texture is said to be poikilitic. One could describe this as “poikilitic hornblende.” The black minerals that are commonly seen in granitic rocks are hornblende and biotite. Biotite is the soft, platy, hexagonal mineral – it’s a mica.


Hornblende and hybridized mafic enclaves


Amphibole cleavage in hornblende



Hornblende:

http://en.wikipedia.org/wiki/Hornblende


Biotite:

http://en.wikipedia.org/wiki/Biotite


Poikilitic texture:

http://en.wikipedia.org/wiki/Poikilitic



Here are a few from a boulder on the shore of Bear River Reservoir, Sierra Nevada:


No shortage of hornblende in this boulder…


Lots of hornblende and small mafic enclaves


Closer view, showing poikilitic texture in hornblende

crunch

Social climber
CO
Jan 16, 2010 - 04:06pm PT
Tuolumne Tradster's aerial photo a few posts back is of Canyon de Chelly. The big tower is Spider Rock, 800 feet high. The chunky butte just right is Arachnid Mesa, a Todd Gordon FA. You can see part of the road leading to the overlook. That's a lot of snow. Brrrr.
Fritz

Trad climber
Hagerman, ID
Jan 16, 2010 - 04:34pm PT
Minerals:

You (of course) are correct on the first two photos of my quiz.
Epidote & garnet.
Chrysocolla over garnet.

On the 3rd photo of the Mystery Metallic Mineral (3M), I am not sure about the chlorite, and the white is quartz not calcite.


I will post another photo of a more oxidized piece of the 3M.
The mine is on a "tactite deposit, formed by the alternation of limestone blocks by mineralizing solutions from a quart diorite stock".

Specific metallic minerals listed for this mine are: cuprite, chalcocite, covellite, bornite, chalcopyrite.

The 3M does not match up to the dark mineral in your first photo. The 3M seems to be in thin layers or books at this site.

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 04:52pm PT
crunch: thanks for the canyon id. One of these days I'll have to check out Canyon de Chelly from the ground.

Minerals: your mystery black mineral is in a metamorphic rock...correct? I guessed hornblende because I've seen amphiboles in metamorphic rocks that have that crystal form.
Minerals

Social climber
The Deli
Jan 16, 2010 - 05:13pm PT
Ahh, OK, Fritz. I was having a hard time seeing your original photo – the darker patches that I thought were chlorite are shadows on the epidote. Quartz on the left? Is the shiny stuff in the lower right the 3M or a reflection off a cleavage surface on a non-metallic mineral? I will have to give your second 3M photo some thought. Sure doesn’t look like chalcopyrite or bornite (“peacock ore”). Must be a copper mine.

Well, if the 3M doesn’t match up to my metallic mineral photo above, then we might as well turn it into another quiz! What is it? And what is the main surrounding mineral?


Tradster, yes, the above photo of the mystery black mineral is of a metamorphic rock and the photo on the previous page is of a skarn. This black mineral is a relatively common accessory mineral in pegmatites.
Minerals

Social climber
The Deli
Jan 16, 2010 - 05:28pm PT
OK, Fritz. My guess for the 3M is covellite (CuS) based on your “thin layers or books” description. Had to look it up in my mineralogy text.
Klimmer

Mountain climber
San Diego
Jan 16, 2010 - 05:32pm PT
OK, here is an easy question but an important one.

Q: What geomorphic feature type dominates on all planetary bodies in the Solar System? (Planetary bodies includes planetesimals, protoplanets, dwarf planets, moons, planets (at least this feature dominates on the Terrestrial Planets, not so on the Gas Giant Planets).

The late great Astrogeologist Gene Shoemaker would be proud if you all could get this right, since he really woke us up to this reality.
Minerals

Social climber
The Deli
Jan 16, 2010 - 05:37pm PT
I’ll keep my guess to myself…
Fritz

Trad climber
Hagerman, ID
Jan 16, 2010 - 06:19pm PT
Well Minerals: It's a deep subject. I worked it down to Covellite, but this 3M stuff was hard, and not at all flexible, no perfect cleavage either. Then I thought Chalcocite. It still didn't fit well.

After your answer, something clicked. When I broke open the epidote, garnet,3M specimens: a red powder trickled out. When I thought about it, hematite was the red powder. In my two Geology field reports Hematite is mentioned as common in the district, but not mentioned at this mine. In desperation I tried the streak test on my sidewalk. The streak was red = hematite. I then referred back to "Idaho Minerals" and of course it mentions Hematite in this form at this location.

Hematite = 3M = Mystery Metalic Mineral! I'm sticking to it. Gotta rest now--whew!
Minerals

Social climber
The Deli
Jan 16, 2010 - 06:38pm PT
Hmmm. If you say hematite, then my original guess was right. The photo that I posted is of specular hematite – some of it is metallic and some is more weathered, and darker colored. The streak test will usually do it, though. I thought the brownish color in your second photo didn’t quite fit covellite.


Hematite:

http://en.wikipedia.org/wiki/Hematite

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 09:06pm PT
Klimmer: in response to your question about rocky planet geomorphology, there's a hint in one of my posts further back in this thread.

Minerals: ilmenite?
Fritz

Trad climber
Hagerman, ID
Jan 16, 2010 - 10:09pm PT
OK! After Minerals worked on my difficult mineral ID: I am going to throw up an easy one.

This specimen is from a "iron-rich skarn" in central Idaho.

Photo shows typical crystals of this common mineral.

Klimmer

Mountain climber
San Diego
Jan 16, 2010 - 10:21pm PT
My guess . . .

Magnetite Fe3O4

http://en.wikipedia.org/wiki/Magnetite


How about a streak test color?
Minerals

Social climber
The Deli
Jan 16, 2010 - 10:25pm PT
Ilmenite is found in pegmatites but the jet-black mineral is a little more common than ilmenite. It often has striated surfaces…


Fritz, nice photo – octahedral crystals… I think Klimmer got it.
Reilly

Mountain climber
Monrovia, CA
Jan 16, 2010 - 10:27pm PT
Amphibole cleavage in hornblende

As a geology lurker I love it when y'all talk dirty!
Fritz

Trad climber
Hagerman, ID
Jan 16, 2010 - 10:36pm PT
Klimmer is the winner! A big round of "boooyahs" to Klimmer.

Seriously: the hints were good, but the crystals were not that easy.

Nice job Klimmer.
Klimmer

Mountain climber
San Diego
Jan 16, 2010 - 10:44pm PT
I know my question was easy. You all know it of course . . .

Impact Craters
http://en.wikipedia.org/wiki/Impact_crater


Gene Shoemaker is the man. With the discovery of Comet Shoemaker-Levy 9 and then watching all 20 or so fragements slam into Jupiter, we realized that this indeed can happen in our time. If it can happen to another planet in our lifetime, then it can also happen to Earth. If just one of those fragments of SL9 hit Earth it would have been game over. Just one of those impacts was half the size of Earth or larger. The hunt for NEOs began in ernest.

A great NGS DVD to watch is "Asteroid - Deadly Impact." Goes into this whole story in detail. My students really enjoy it when we study the Asteroid Belt and the differences between Comets (from the Kyper Belt), Asteroids, Meteoriods, Meteors, and Meteorites. Very cool film. I can watch it time and time again. In fact, I do every year with my students. This movie never gets old. Riveting.

National Geographic Video - Asteroids - Deadly Impact (1997)
Starring: Carolyn Shoemaker, Eugene Shoemaker Director: Eitan Weinreich
http://www.amazon.com/gp/product/B00009B8F9?ie=UTF8&tag=ovgcom08-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=B00009B8F9


By the way, there is no other natural disaster that compares to the possible destruction of an Impact. There is a line in the movie where Gene says this and then uses the analogy of all the nuclear armaments on Earth going off at once, and then it would still pale in comparison. Case in point . . .

Asteroid Impact (HD) (music by Pink Floyd):
http://www.youtube.com/watch?v=-zvCUmeoHpw

Nothing like it.


Klimmer

Mountain climber
San Diego
Jan 16, 2010 - 11:02pm PT
Thanks you guys. I'll have to come up with a mineral eventually that will stump you guys, although I will admit I can easily be stumped. I mean how many minerals are there something like 4000 + ?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 11:09pm PT
In 1998 NASA started the Spaceguard Near-Earth Object Survey to identify objects, like asteroids & comets > 1 km in diameter that orbit close to the Sun. The National Academy of Sciences (NAS) is researching methods to divert objects like this that could impact the earth during the next 100 years. Such objects would have ~1 billion tons of mass. Traveling at 30 km/sec, it would have explosive power equivalent to 100 billion tons of TNT. One option being evaluated is to detonate a nuke near an incoming asteroid to divert &/or fragment it.

-Reference: Science & Technology Review, December, 2009. A publication of Lawrence Livermore Laboratory.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 11:12pm PT
Minerals: OK thanks for the hints...black tourmaline
Minerals

Social climber
The Deli
Jan 16, 2010 - 11:13pm PT
Yeah, impacts are big enough to even put a dent in the geologic time scale… at 65!

http://en.wikipedia.org/wiki/Chicxulub_crater


How ‘bout that iridium layer, Klimmer?
Think I originally read about it in a McPhee book.
Minerals

Social climber
The Deli
Jan 16, 2010 - 11:20pm PT
Woohoo! You got it, Tradster! Nice job!


Tourmaline:

http://en.wikipedia.org/wiki/Tourmaline
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 11:25pm PT
Minerals: check out the pegmatitie counter top we just installed at our cabin in Monte Rio.

Klimmer

Mountain climber
San Diego
Jan 16, 2010 - 11:29pm PT
Yep, the iridium layer that the geologist father and son team discovered and led them to the theory of the impact demise of the dinosaurs at 65mya is well represented in the above mentioned movie. They are interviewed and show the layer and what it looks like, and how they made the discovery. Very cool.


OK, lets mix it up. Here is a mineral property that is very cool to look at Flourescence!

I will make it easy.

This type local for the following flourescent minerals is World Famous and here in the good ol USA.

3 questions:

What is the name of the famous type local for these well known flourescent minerals in the following image? These minerals are all from the same famous local.

What is the mineral that floureses bright orange in these rocks?

What is the mineral that floureses bright green in these rocks?

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 11:33pm PT
Also an Eocene impact in Chesapeak Bay
http://en.wikipedia.org/wiki/Chesapeake_Bay_impact_crater

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 16, 2010 - 11:39pm PT
Willemite/Calcite
Franklin, New Jersey
Orange red calcite, Green willemite

Klimmer

Mountain climber
San Diego
Jan 16, 2010 - 11:50pm PT
Ding. Ding. Ding.

You are correct.

I love flourescent minerals.

I really love it when I find a mineral that looks beautiful in natural light, along with really interesting crystal habit, and then turn on my "Way Too Cool" powerful short wave UV lamp and the color just pops! Major wow factor! Multiple bangs for the one find or purchase.

I think Fritz posted about TG&MS already. I'm getting excited just thinking about it. TG&MS, the finest Gem and Mineral Show in the World.

We are blessed every year with the Tucson show.
Minerals

Social climber
The Deli
Jan 17, 2010 - 12:08am PT
Wow, cool stuff! Neat fluorescence and sweet diagrams of Chesapeake Bay, especially the cross section! This planet could use another good knocking…



The rock on the left is granodiorite. The rock on the right is aplite (dike). What rock type/texture describes the vertical band of rock in the center of the photo? What is going on here?



Minerals

Social climber
The Deli
Jan 17, 2010 - 12:23am PT
In general terms, what kind of rock is this? (Photo is a close-up)


Klimmer

Mountain climber
San Diego
Jan 17, 2010 - 12:32am PT
Total stab in the dark . . .

1st photo, seam or dike of plagioclase?

2nd photo, looks like it is being squeezed and sheared, with another mineral type forming between, so in the generalist of rock types - Metamorphic Rock.
Minerals

Social climber
The Deli
Jan 17, 2010 - 12:37am PT
Correct on the second photo in that it is a metamorphic rock. What kind of metamorphic rock – protolith?
Minerals

Social climber
The Deli
Jan 17, 2010 - 12:37am PT
What is this mineral?

Minerals

Social climber
The Deli
Jan 17, 2010 - 01:21am PT
Looks like some nice countertop material there, Tradster! Is the black mineral tourmaline or big biotite? I bet there’re some cool textures in the feldspars. We just have regular granite with smoky quartz in the kitchen here, but it’s got a bit of a wavy foliation to it here and there. (Got tired of freezing my ass off and getting sick in the cold so rented a room at the end of last month…)


tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 17, 2010 - 01:22am PT
my guess for the mineral 2 posts above is sphalerite

the protolith for the metamorphic rock is a tough one...my WAG is a porphyritic volcanic rock

the black minerals in our countertop pegmatite are biotite & hornblende. I'll look next time I'm up there to see if there is any tourmaline and take some close up photos. Definitely some very cool twinning and exsolution (perthitic?) textures in the feldspars.
Minerals

Social climber
The Deli
Jan 17, 2010 - 01:36am PT
It does look like sphalerite, but it’s in a different set of minerals. The photo was taken near May Lake, Yosemite.

The orange color in the metamorphic rock is surface staining and your WAG is correct – porphyritic metavolcanics east of Tioga Pass.

Yeah, perthite (perthitic feldspar/perthitic texture/etc.) and maybe some graphic textures as well… Good stuff!
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 17, 2010 - 01:47am PT
Minerals: are these photos of minerals you are posting part of your personal mineral collection?

I had a very nice mineral collection that I had accumulated over ~20 years that got stolen from a storage space. I miss that mineral collection.
Minerals

Social climber
The Deli
Jan 17, 2010 - 02:16am PT
Tradster, that sucks that your mineral collection was stolen! You have to wonder when someone steals ROCKS! Did you have any valuable samples?

Pretty much all of the photos that I have been posting were taken out in the field, with the exception of the wollastonite sample and the following garnet/tourmaline sample. I have over a ton of rock in storage (literally) and maybe I can find a few more samples to dust off and photograph. A lot of it is pretty buried.


A mini collection:

Pebbles on the tailgate for show-and-tell with my friends last June. Most of the minerals should be relatively obvious.




tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 17, 2010 - 04:24pm PT
I didn't have any valuable minerals in my collection but they were valuable to me because they represented memories. One of the samples was a dense, grapefruit-size mass of garnets from the Gunmetal mine. Another was a sample of the Beck Spring dolomite from Death Valley that contained a contact between stomatolites and pisolites.
Fritz

Trad climber
Hagerman, ID
Jan 17, 2010 - 09:35pm PT
Minerals: I am also stumped on your last mineral posting: with the measuring stick. Nothing in granitic rock, that I have seen, matches up with your photo. Tradster guessed Sphalerite---I can't think of anything.

OK! If we are going to be tough-----here are two minerals from the same iron skarn that the Magnetite in my last question came from. Both occur very close to the Magnetite.

This one is common, but you don't see crystals or color exactly like this commonly.


This one is very-rare in crystals this size. They are frozen in marble and some are right next to Magnetite. Anyone that guesses this one: is a geologist god!



Minerals

Social climber
The Deli
Jan 18, 2010 - 01:44pm PT
Yeah, Tradster, I know what you mean about rocks having sentimental value. I would be so bummed to lose my collection, or even just a few of my favorites. Large masses of garnet can be pretty cool looking. Still want to go check out the Gunmetal mine at some point here – maybe I can grab some garnet for you!


As far as my last mineral quiz, yes, the mineral is hosted in a granitic rock (of sorts) but it is also a common skarn mineral. There is one small area of the mineral in the photo that gives a clue as to what it is…


Fritz, you have a nice collection there. Great photos!

OK, I’ll give those a shot.

The first one looks like vesuvianite/idocrase, based mainly on its crystal structure, but also because of color and your description and where you found it (skarn deposit).

The second one looks like scapolite.

Minerals

Social climber
The Deli
Jan 18, 2010 - 02:51pm PT
A hint on the first photo quiz on this page, the one with the vertical band:

This is not an igneous texture…
Fritz

Trad climber
Hagerman, ID
Jan 18, 2010 - 04:25pm PT
Minerals: re my difficult mineral ID and your answer:
The first one looks like vesuvianite/idocrase, based mainly on its crystal structure, but also because of color and your description and where you found it (skarn deposit).

That crystal does scream vesuvianite, but there is not supposed to be any at the site, and I did mention it wasn’t a typical crystal. A very close guess, though.

I’ll post a more typical crystal.



On the next photo of the crystals in marble: another good guess, but this one is very, very rare. (without refering to a geology text that covers the site: I would not have figured it out---ever.)

Here is another camera angle on the specimen.

Minerals

Social climber
The Deli
Jan 18, 2010 - 05:17pm PT
Fritz, on the first mineral, I thought you meant that it usually didn’t form well-developed crystals and is usually more massive in habit. I didn’t understand that the first photo shows an atypical crystal structure/shape. Thanks.

OK, my second guess on the first mineral: apatite?


So, you are saying that the second mineral is a really weird one? Hmmmm… I’ll have a look but don’t know about that one… Your second photo does help, though.
Fritz

Trad climber
Hagerman, ID
Jan 18, 2010 - 05:38pm PT
Minerals: On the first photo, go back to silicates. You were much closer on your first guess of Vesuvianite.

Here's a photo looking down on the largest crystal of the first specimen.
Minerals

Social climber
The Deli
Jan 18, 2010 - 05:58pm PT
Whew… These aren’t easy or I am being retarded! I thought apatite because you mentioned that it was close to the magnetite and just read about the common occurrence of apatite with magnetite/iron ore bodies.

OK, how about diopside (pyroxene)?

And a WAG on your second mineral… manganite?
Fritz

Trad climber
Hagerman, ID
Jan 18, 2010 - 06:12pm PT
Minerals: Diopside it is! As you said, identifying minerals from photos is difficult.

Second guess wasn't bad. However the mystery mineral is a mix of MG, FE, B, and Oxygen. No commercial value, and I think only of slight interest to collectors.

I like those black minerals more and more though!
Minerals

Social climber
The Deli
Jan 18, 2010 - 06:35pm PT
Yeah… it is difficult! Not quite like having the sample in your hand, with a hand lens in the other…

I was thinking diopside after you said that vesuvianite was close, but for some reason it didn’t look right and I went with apatite, which made me hungry. Mmmm, mini Clif Bars…

I don’t see anything with Mg, Fe, B, and O in my text. But I thought it might have iron in it, based on the “limonite” staining and the occurrence with magnetite. Manganite is the only one in my text that was close. What mineral is it? A borate?
Fritz

Trad climber
Hagerman, ID
Jan 18, 2010 - 08:57pm PT
Minerals: It is Ludwigite and is a borate.


http://www.mindat.org/min-2454.html

Only mineral collecting I have ever engaged in, where I was worried about a cornice falling on me.

Minerals

Social climber
The Deli
Jan 18, 2010 - 09:16pm PT
Ludwigite? Never heard of it… but now I have. It’s not listed in my field guide to rocks and minerals or my Manual of Mineralogy, but it is listed in Hibbard’s mineralogy book, briefly. I never would have found it. Good one Fritz! I will try to come up with a few more here at some point…
dipper

climber
Topic Author's Reply - Jan 21, 2010 - 12:57am PT
Folks,

I am very much enjoying all the rock talk goin' on here.

Please continue.

I have been rummaging around the terabytes and found these two.

Any takers?











Shack

Big Wall climber
Reno NV
Jan 21, 2010 - 01:01am PT
That's too easy...I'll let someone else have a chance. ;]
dipper

climber
Topic Author's Reply - Jan 21, 2010 - 01:14am PT
Two more, these are at the southern end of the Sierra in the Golden Trout Wilderness









Detail of the above rock
Studly

Trad climber
WA
Jan 21, 2010 - 01:30am PT
are the first two photos shale and malachite?
Last photo a form of quartz perhaps?
Minerals

Social climber
The Deli
Jan 21, 2010 - 01:23pm PT
Well… gotta say… Wall climbing photos and geology are a hell of a lot more interesting than silly politics and those other random subjects that seem to keep people so entertained… Oh, well.

Glad you have been enjoying this thread, Dipper, and hope that it has been helpful/educational to others as well. As climbers, I think we owe it to ourselves to know at least a little bit about the rock that we enjoy climbing on so much. And, geology is fun too!

Thanks for your post, Studly! I hope more of you will join the conversation, before Fritz and I go through our entire mineral collections! ;)


Dipper, your first photo is beautiful! I scrolled down, and for the first millisecond that I saw that photo, my brain said… flow banding in obsidian! But then my eyes saw the rest of the photo and the background… and I took a closer look at the rock. It’s certainly not obsidian! Is that the summit of a peak or near the summit? Owens Valley in the background?

The rock in the foreground looks granitic to me, based on color and the way it fractures. The banding seen on the surface of the outcrop appears to be more hydrothermal alteration along fractures/weaknesses; the “bleached” plagioclase gives the bands the lighter color. Visually speaking, this alteration seems to be accentuated by surface weathering – aside from the lighter-colored bands, the weathered surface of the rock is darker in color than the freshly broken surfaces, although I think I can just barely see the banding continue on the fresh surfaces. If the banding in the rock were due to the segregation of different colored minerals within the rock, then we would expect to see the banding continue through the rock and on the fresh surfaces, which we don’t see. I’d guess that this rock is granodiorite or diorite, based on color. The rock in the upper left of the photo is either a section of the same rock type that has not been altered or it is a dike or larger intrusion of another rock type, with the transition representing the contact between the two different rock types. The brown-colored rock in the lower right looks like some sort of metamorphic rock, based on color.

Doesn’t look like malachite in the second photo. What other green minerals have we discussed so far? How about the brownish spots just left of center and the black stuff in the lower right? I’ll leave the lichen to the bio-types.

If the sun ever decides to show itself again, I’ll take some more mineral photos to post.


OK, Shack… You keep all the answers to yourself and I promise not to tell them anything about CT scanners! :)

Minerals

Social climber
The Deli
Jan 21, 2010 - 01:25pm PT
Still looking for a rock-type name and a mineral name, from my quizzes on the previous page… Or should I spill the beans?
Klimmer

Mountain climber
San Diego
Jan 21, 2010 - 02:40pm PT
Ok, the image above with "Banding" pattern is in the Sierras. I can see the volcanic cinder cones on the Eastside of Owens Valley N. of Independance and S. of Big Pine. Hey, location helps.

The banding as Minerals has pointed out doesn't look like it is through the rock. I can't see the banding pattern on the broken faces facing the camera. So, is it just a surface pattern? Don't know. Hard to tell.

Flow Banding does happen in igneous rock but kinda rare. If it is igneous rock with flow banding, then it is an unusual phenomenon. And the igneous rock would be . . . ahhhh, hold on a minute, looking up table on classification of igneous rocks. Ok, my best stab in the dark would be: Igneous, Intermediate, Extrusive with flow banding, texture looks fine-grained, so = Andesite. Edit: ok, if it is intrusive then it would be Diorite.

Could it be metamorphic? Hard to tell. Can't touch a picture. Hard to figure out . . .


3rd image of unusual cleavage pattern on boulder in the Sierras? When all else fails throw-out Plagioclase, Feldspar! It is bound to be the answer eventually. Lite in color minerals are hard to distinguish if you can't look at it, hold it, test it.

Ok, so how bad did I do?
Studly

Trad climber
WA
Jan 21, 2010 - 02:47pm PT
I am pretty ignorant about rock identification, would love to know more. Klimmer you said the top photo might be andesite. I climb on andesite up here in the Columbia River Gorge area a ton, and that looks like no andesite I have ever seen. Could it be that completely different? As rarely does andesite appear to have regular patterning, it is more random and weathers completely different then that phots, as least in my experience up here.
dipper

climber
Topic Author's Reply - Jan 21, 2010 - 03:32pm PT
Minerals,

I figured that was epidote. But it was too nice to not post.

Here is a tighter shot of that ridge top you like. It is pretty big, but I figured the detail was worth it.

It is on the ridge east of Mt. Baxter. That whole area is amazing even to me.

I imagine you pro rock-heads would go nutz.

When it stops raining, I will dig out some of my smaller ballast and take some pics.

I have two small cannon-ball like objects from this area. They are layered like an onion, about the size of a baseball.




Klimmer

Mountain climber
San Diego
Jan 21, 2010 - 03:44pm PT
It is cleaving along the banding pattern, that indicates it is Metamorphic to me now. But what kind of metamorphic rock? I'll come back later.
Minerals

Social climber
The Deli
Jan 21, 2010 - 06:58pm PT
Hey, Studly, I think you know more about rocks than you think you know. How many non-geologist, non-climbers can look at a rock or even a photo of a rock and say… Nah, that doesn’t look like such and such, it looks more like this and that… We climbers get to see a lot of rock, but as obvious as that may sound, there are a lot of geologists out there who wish they could see all the things that we see. And after climbing for a little bit, you get to know the rock, whether it is here or there, this or that, how it feels and what it looks like up close and… hey, what are those things that you are hanging on to…?


Hey, how about the book Flakes, Jugs & Splitters: A Rock Climber’s Guide to Geology?

I think Sarah summed it up nicely in her second to last post (7/5/09) in this thread:

http://www.supertopo.com/climbers-forum/884866/the_geology_of_rock_climbing


Some neat geology in the thread, as well! Where are you guys?

Minerals

Social climber
The Deli
Jan 21, 2010 - 06:59pm PT
Klimmer, good point about the rock cleaving along the banding – that does seem more apparent in Dipper’s second photo. I still think it looks like an intrusive rock. The dominant set of joints in both photos is oriented perpendicular to the banding. If the banding represents foliation/layering in a metamorphic rock, I would usually expect the dominant joint set to be parallel to the foliation/banding, which it isn’t. The freshly fractured patches of rock in the first (larger) photo don’t seem to follow the banding pattern. The loose chunks don’t have the shape that one would expect of a foliated metamorphic rock and they just have that “granitic look” to me – shapes, angles, texture… The planar surface that shows banding is probably another joint surface that has been exposed to more fluid flow/weathering than the rest of the rock.


Yeah, Dipper, looks like epidote. Tough to tell what the other stuff is from the photo. The Mt. Baxter area looks cool – there is so much neat stuff in the High Sierra, more than a lifetime of exploring to be had… I will keep that area in mind.

“I have two small cannon-ball like objects from this area. They are layered like an onion, about the size of a baseball.”

Hmmmmm… Granitic? Layered as in weathering or layered as in mineral composition? Have you found a couple of orbicules? Or maybe not…?



Minerals sayz... WOW!

Image from Wikipedia, found here:
http://en.wikipedia.org/wiki/Orbicular_granite


I hear that there is some orbicular granite to the west of Donner Pass but haven’t been out to find it yet – a professor (Hibbard) told me about it and put a dot on a topo map. Now I just need to find that map… :)

corniss chopper

Mountain climber
san jose, ca
Jan 21, 2010 - 07:04pm PT
Horse Creek , Northern edge of Yosemite NP.
Minerals

Social climber
The Deli
Jan 21, 2010 - 07:24pm PT
Looks like there’s a story behind that one, Corniss Chopper.



Hmmmm… Hey Dipper, are those angular chunks of granite in your second grey rock photo? I am having a hard time seeing the details on this laptop screen. If so, and they are not deformed, then that pretty much sums it up.
50

climber
Stumptown
Jan 21, 2010 - 08:44pm PT
Came across this story today that a few of you petroleum geologist might enjoy...

http://www.vacationideas.me/asia/the-door-to-hell-burning-gas-crater-darvaza-turkmenistan/

Darvaza Burning Gas Crater
Turkmenistan is very rich in natural resources. Currently a sovereign country, Turkmenistan was part of the Soviet Union until 1991. It was during rule of Soviet Russia, back in 1971 when geologists were conducting gas drilling in Kara-Kum desert and discovered an underground chamber close to the village of Darvaza (known in Turkmen as Derweze, but sometimes also referred to as Darvaz). The discovery of the chamber was accidental and resulted in drilling rig collapsing, leaving giant gas crater filled with poisonous gases exposed to the world outside. The concentration of gases within the crater was high so nobody dared to go down there. It was then when someone came with an idea to light the gas in the crater on fire so as to burn it before the poisonous fumes engulf the nearby town of Darvaza.

The geologists thought the idea of burning the gas was smart and went ahead with lighting the crater on fire. As it turns out, the supply of quality natural gas below the crater is near infinite as the crater’s been burning since. At the time of this post, on June of 2009 the gas crater in Darvaza is still burning and has been since 1971 without interruption. No one can even imagine how much quality natural gas was burnt throughout the 38 years of the crater being on fire. No one can estimate how much more gas there still is. When they first lit the gas crater on fire, they thought the fire would go out after a few days. It’s been more than a few day, it’s been more than a few weeks or months. It’s been decades and the gas crater is burning just as it did the day it was first lit. Putting all economical loses from wasted natural gas aside, imagine the ecological impact this burning gas has cause during decades of non stop burning!



tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 21, 2010 - 09:18pm PT
cool photos everyone

corniss chopper: is that horse creek peak?

50: interesting story...thanks for posting that.
Minerals

Social climber
The Deli
Jan 21, 2010 - 09:55pm PT
Yeah, really cool article, 50! Thanks. Do they do primitive sacrifices there when the tourists are away? >:)>



Quoting myself from above:

“The dominant set of joints in both photos is oriented perpendicular to the banding. If the banding represents foliation/layering in a metamorphic rock, I would usually expect the dominant joint set to be parallel to the foliation/banding, which it isn’t.”

I need to correct myself on this. The “dominant” joint set or cleavage in a metamorphic rock does not always have to be parallel to the foliation – it can be common to see a well-foliated rock that is jointed at high angles to the foliation. I guess what I was trying to say is that as far as an obvious cleavage in the rock, the main section of outcrop in the first photo looks pretty solid (aside from the main joints). As a whole, the rock just doesn’t have that planar metamorphic weakness look to it (foliation, etc.) and the lighter-colored banding looks like alteration. In some places, the rock is cleaving along the bands; the alteration bands probably formed along tiny parallel fractures, which are a slight weakness in the rock. The darker color on the planar surface could also be mineralization (tourmaline, amphibole, pyroxene, etc.) that formed along the joint at the same time as the alteration (white bands). There may even be tiny bits of epidote in there too!



OK, how’s about this? Where is it? (Where else could it be...?) How many different rock types? Names of rock types? What’s older and what’s younger? And while we’re at it, name the two routes!


tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 22, 2010 - 02:37am PT
I'm no aficionado but that's el cap between the NA Wall & East Buttress

here are my WAGs RE the routes...
Lost in America & Born Under A Bad Sign

from oldest to youngest...
El Cap Granite
Granodiorite
Diorite & Gabbro? dikes cutting El Cap Granite

looks like there might be some younger cross-cutting quartz-feldspar rich dikes but can't tell from this photo, could be weathering features.

Some of the contacts between intrusive rock types are quite linear and look more like fault? joint? contacts than intrusive contacts.

What does this sequence indicate about the chemical evolution of the magma chamber(s)?

Is there any Taft Granite visible in this photo or is that granite located higher up on el cap?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 22, 2010 - 02:56am PT
This is a GoogleEarth image from northern foothills of the Avawatz Mts just south of Death Valley that was mentioned in one of the early posts to this thread. The NW-trending light colored rock in the center of the photo is pre-Cambrian granite-gneiss in the core of an anticline that is flanked by Pleistocene-Quaternary Playa Lake, Evaporite, and Alluvial Fan deposits. This structure is located at the southern terminus of the Death Valley fault zone where it merges with the eastern terminus of the Garlock Fault zone.
Minerals

Social climber
The Deli
Jan 23, 2010 - 01:33pm PT
Tradster, I missed your new posts the other day. Yeah, Lost in America on the left; the other route is an “easy” route…

Good work on the El Cap rock types. Guess I need to do some El Cap typing at some point here. Would help if I had the Ratajeski/Glazner paper in front of me…

Cool image! Your field area? GoogleEarth RULES!!!
Minerals

Social climber
The Deli
Jan 23, 2010 - 01:34pm PT
Well, after Fritz’s difficult mineral quizzes, how about some easier ones…



What is the “blue iridescent” mineral that makes up most of this rock?

Polished surface of countertop slab material scrap



The white mineral is calcite (notice the rhombohedral cleavage). What is the other mineral?


Minerals

Social climber
The Deli
Jan 23, 2010 - 01:58pm PT
Thanks, BASE104. Here’s an image of Yosemite Valley – the joint sets are rather obvious and in some area, control the shape and orientation of the Valley. GoogeEarth might be better…

Yeah, strain (deformation in a rock) results from stress (force).


Image found here: http://rst.gsfc.nasa.gov/Sect6/Sect6_9.html
gstock

climber
Yosemite Valley
Jan 23, 2010 - 02:00pm PT
I've always considered the rock face near the fifth pitch of Tangerine Trip to be the most beautiful on El Cap, and seeing it up close confirmed that for me. The combination of near-horizontal aplite dikes and vertical orange and gray water stains is really spectacular. Fun lower-out from there also!

Greg

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 23, 2010 - 06:18pm PT
Minerals: The blue iridescent mineral above is labradorite.
My WAG for the mineral associated with the calcite...chlorite?

Cool photo of Yosemite Valley...really shows how regional joint patterns control valley/canyon orientation. In the case of Yosemite Valley these joints are essentially orthogonal...NNE-SSW and the other WNW/ESE

Here's a photo I took a couple of weeks ago on a flight from Oakland to Phoenix. I believe the area is Sequoia/Kings Canyon but not sure. In any case, the snow-filled gullies show what appears to be a conjugate joint pattern in the granite.
Minerals

Social climber
The Deli
Apr 2, 2010 - 07:42pm PT
This thread is not dead!!!


Yeah, Tradster, looks like at least a couple of joint sets on that snow-covered ridgeline. Cool! Yes, you are correct on the blue mineral – labradorite, a variety of plagioclase feldspar that is commonly used for countertops because of its neat iridescent color. The second mineral with the calcite is not chlorite, but it is soft. Close guess.


Labradorite:
http://en.wikipedia.org/wiki/Labradorite


Man, I’ve got more catching up to do in this thread…


But for starters, how ‘bout that photo that Dipper posted a little while back, from the ridgeline east of Mt. Baxter?

Dipper’s post up-thread with original photo found here:

http://www.supertopo.com/climbing/thread.php?topic_id=1048215&msg=1064721#msg1064721


With the help of Tuolumne_Tradster, I have learned how to overlay geologic maps onto Google Earth. WooHoo! Thanks, man!!! So, with the view in Dipper’s photo as a reference, I tried to figure out where the photo was taken from, using Google Earth. I wasn’t able to attain the exact perspective because I couldn’t go low enough without bumping into the ground, at which point the eye elevation and angle of view jump and then things get all out of whack (seems like a bug in the software to me…). Anyways, this was about the best I could get – the foreground has no texture because, out of all of the satellite coverage in the Sierra, THIS area had to have some cloud cover. Oh, well… You get the idea.


Dipper’s original photo from the ridgeline east of Mt. Baxter
(Hope you don’t mind that I borrowed it!)



Google Earth view in 3-D, looking NNE, from the approximate location where the above photo was taken. Notice similar features (topography and color) between photo and 3-D image; foreground is obscured by “cloud cover” and lacks ground view



Same view as above but with a map overlay - USGS Mount Pinchot Geologic Quadrangle



View showing Mt. Baxter and the ridgeline to the east where I have approximated the location of Dipper’s photo. The transparency of the geologic map overlay can be adjusted in Google Earth such that the base image can also be seen, as you can see in this image



Another view, slightly different than the previous, but with the geologic map overlay set at 100% (0 transparency… political remarks withheld…;)



Google Earth map view of the Mt. Baxter area. Based on my approximation of the location of Dipper’s photo, the rock in the photo is mapped as “Km”



Cropped section of the USGS Mount Pinchot Geologic Quadrangle map, showing the Mt. Baxter area. Note unit “Km” as seen in previous image. Also note that the summit of Mt. Baxter is composed of unit “Kta”



For more detail and info, and an explanation of geologic map units, the full map can be found here:
USGS Mount Pinchot Geologic Quad Map (5.84 MB):

http://geomaps.geosci.unc.edu/quads/fulls/Mount%20Pinchot.jpg


From the explanation of rock units:

Km – Mafic plutonic rock
Mafic granodiorite, quartz diorite, diorite, gabbro, and peridotite. Commonly intimately mixed with granitic material and metamorphic rocks and cut by granitic dikes. Includes dikes of remobilized mafic plutonic rock.”


This unit (Km) is mapped as the oldest plutonic (intrusive igneous) unit in the map area. With that considered, it is even more likely that the rock has been altered (striations in Dipper’s photo), given its older age and the subsequent igneous activity in the surrounding area. The lighter blobs/chunks of rock in the lower right of Dipper’s photo may be part of the “granitic material” and/or “granitic dikes” mentioned in the unit description above.


Kta – Tinemaha granodiorite
Woods Lake mass. Slightly porphyritic granodiorite and quartz monzonite”



The many red lines on the map are mafic dikes (dark in color) of the 148 million-year-old Independence Dike Swarm. Note that units older than 148 Ma are cut by the dikes, yet units younger than 148 Ma truncate the dikes – simple cross-cutting age relations.

Some info on the Independence Dike Swarm:

http://geology.geoscienceworld.org:80/cgi/content/abstract/7/3/129

http://gsabulletin.gsapubs.org/content/112/3/504.abstract

http://www.geolab.unc.edu:80/Petunia/IDS_Web_Site/FTG.html
(lots of info)



Additional geologic quad maps of the Sierra Nevada can be found here:

http://geomaps.geosci.unc.edu/quads/quads.htm


Geologic maps of Yosemite Valley as well as the entire Park can be found here:

http://geomaps.geosci.unc.edu/parks/parks.htm


Enjoy!

Minerals

Social climber
The Deli
Apr 2, 2010 - 08:25pm PT
Wes, Tradster is correct, although we are leaving out Taft granite. The North America diorite cuts older El Cap granite and hybrid tonalite dikes. The aplite/pegmatite dikes and pods are the youngest intrusions on the face.

I don’t know anything about Squamish, but I would guess that the granitic rock is Cretaceous in age. Nice photo. That dike looks quite linear, with sharp contacts with the host granitoid. My guess would be that the dike is a Tertiary basaltic dike that fed surface volcanism above. It is quite common to see Tertiary mafic dikes cutting Mesozoic granitoids in the Nevada desert.

The relations between the various rock units on El Cap are quite interesting and somewhat complex – the SE face is an amazing window into the workings of plutonic systems. I should write more on that…
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 2, 2010 - 08:33pm PT
Awesome Minerals...looks like you've put the GoogleEarth geologic map overlays to good use.

Timid TopRope...interesting problem...will have to think about this one.
Minerals

Social climber
The Deli
Apr 2, 2010 - 08:54pm PT
Yeah, Tradster, Google Earth is freakin’ AWESOME! What an amazing tool. Thanks again for all of your help with that! I’m psyched.

OK, I will try to start thinking about El Cap again. But I feel a little hesitant to write too much without Ratajeski’s paper in front of me, which is filed in storage. (Note to self… get bolt kit and geo files from storage…)

The wannabe igneous petrologist in me thinks that Timid’s third photo kinda looks like the surface of a volcanic flow. Are those petroglyphs petrified?


“btw, anyone want to assess the stability of One Of These Days wall in Woodfords? I'm sure it will probably stay there until we get a big shake, but it always kinds sketches me out.”

Sounds like a job for Greg and Cleo! Although I might be able to relate to the climbing part…
Minerals

Social climber
The Deli
Apr 2, 2010 - 09:13pm PT
Correct, Wes.

Ratajeski, K., Glazner, A.F., and Miller, B.V., 2001, Geology and geochemistry of mafic to felsic plutonic rocks in the Cretaceous intrusive suite of Yosemite Valley, California: Geological Society of America Bulletin, v. 113, p. 1486-1502.

http://bulletin.geoscienceworld.org/cgi/content/abstract/113/11/1486



Hope Valley? Looks like granite! All I know is that I spent a night in the truck there late November and froze my adze off, and then got sick! Ug. What’s with Hope Valley?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 2, 2010 - 10:28pm PT
Timid: I agree with Weschrist's interpretation...that's basically what I was going to say.

Weschrist: what hydrogeology project are you working on?
nature

climber
Tucson, AZ
Apr 4, 2010 - 03:24pm PT
where is your field area?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 4, 2010 - 05:10pm PT
Weschrist: sounds like an interesting project. So you're looking at spatial heterogeneity in glacial deposits overlying fractured bedrock and how these features influence snow melt recharge of a down gradient wetland? Have you considered using tracers, noble gases, or isotopes like 3H/3He, Rn-222, or Cl36 to evaluate the age distribution of water in the system?

https://ipo.llnl.gov/?q=technologies-groundwater_age_dating

Nimz, G.J., Smith, D.K., Caffee, M.W., Finkel, R.C., Hudson, G.B., Borchers, J.W., and Nimz, K.P., 1992. Isotopic characterization of hydrologic structure and chemical interaction between groundwater and granitic rock in the Wawona basin, Yosemite National Park. Eos, Transaction, Am. Geophys. Union, 73: 170.
Fritz

Trad climber
Hagerman, ID
Apr 4, 2010 - 10:09pm PT
On the
YOUR WILDEST TRUNDLE thread /quote] I ask this question?

So------what is the odor from a freshly trundled boulder after impact???

We always thought it was ozone???

Fresh, sharp, and stimulating------and it is not sulphur.

http://www.supertopo.com/climbing/thread.php?topic_id=1135891&tn=0

Anders asks those that frequent this thread to answer my question.

What do you know?

Thanks, Fritz
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 8, 2010 - 04:34pm PT
some hydrogeo eye candy...Digital Optical Televiewer images obtained from a 160 ft, 6-inch diameter borehole yesterday in the late Miocene, Neroly Fm in the Altamont Hills, CA. These are oriented 2D images of the borehole wall such that south is the center of the image; north is on either end; east is midway between center and left side; west is midway between center and right side.

This image is from ~139 ft in the vadose zone showing a south-soutwest-dipping (~8 degrees) contact between clayey siltstone and fine-grained sandstone

This image is from ~154 ft showing the water table at about 153.4 ft just above a fractured zone from 154 to 156 ft. We plan to screen this well with 8-inch Schedule 80 PVC casing from 130 to 160 ft as an injection well to discharge treated effluent from a nearby groundwater treatment facility that is removing TCE and perchlorate from the ground water.
50

climber
Stumptown
Apr 10, 2010 - 07:49pm PT
Sweet images Tradster and a welcome distraction from Turbotax today.

The shading contrast between the siltstone and sandstone shows a nice contact. So is the clayey siltstone the darker material in the upper portion of the image? Not sure what to make of the features below the contact. What kind of rig was used to drill the borehole? Any comments on why you have to use an injection well for the treated groundwater as opposed to discharging to surface waters?

OK, back to itemized deductions.
cintune

climber
the Moon and Antarctica
Apr 10, 2010 - 08:16pm PT
More geo-eyecandy; some nice differential erosion at Turnip Rock, Lake Huron:
http://www-personal.umich.edu/~jensenl/visuals/album/2009/portaustin/
Klimmer

Mountain climber
San Diego
Apr 10, 2010 - 08:23pm PT
That erosional phenomenon "seastack" in Lake Huron looks very cool. Begs to be climbed. Even sedimentary sandstone has its wonderful moments.

Looks like a scene from a Roger Dean painting. Very cool.

And we all known that Roger Dean was an incredible inspiration for Cameron's Avatar don't we, even though he gives Roger no credit. Geeeeeeeeeesssss.

http://www.rogerdean.com/

The Dean of Avatar
http://lcomics.blogspot.com/2010_01_01_archive.html#2757243822558558354

http://io9.com/5426120/did-prog-rocks-greatest-artist-inspire-avatar-all-signs-point-to-yes/gallery/
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 12, 2010 - 03:35am PT
Ya was doin' TurboTax this weekend too...finally got through it...all I need now is for the CFO (aka Ingrid) to review & approve it so I can submit it.

WOW cintune that photo of Turnip Rock is wild...I've never seen that before...thanks for posting it. Looks like an image in a Salvador Dali painting.

weschrist...in the 1st Optical Televiewer image I posted above, the clayey siltstone overlies the sandstone. That could be bioturbation in the sandstone.

Edge

Trad climber
New Durham, NH
Apr 29, 2010 - 12:52pm PT
I picked this case up at a yard sale a while back and forgot about it. I just rediscovered it today in my wood shop.

I had this very same kit when I was a kid. This brought back memories of specific gravity tests, burning sulfur to see what it smelled like, and blowing through a little pipe attached to an alcohol lamp. I never did get the hang of continually blowing through the pipe without stopping to inhale; a skill that would have translated nicely to playing a didgeridoo. This kit started a long standing interest in all things geologic.

The case in the photos came only with the original test tubes and rack, and the alcohol lamp and blow pipe.


Don't they look like they are having fun?

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
May 18, 2010 - 09:14pm PT
Geo-enthusiasts: check out this photo taken last week in the Altamont Hills, CA. There is a 1 to 2 week window in the early spring when the natural grasses are turning from green to brown when this pattern emerges. The grass remains greener longer along joint/fracture patterns due to higher levels of soil moisture.

HighTraverse

Trad climber
Bay Area
May 18, 2010 - 11:14pm PT
I know from nuttin' about geology. Except maybe, sometimes, I can tell Granite from Sandstone. Oh, and usually I can recognize the Franciscan formation.
What's that dark, craggy rock in the middle of the gully?
kpinwalla2

Social climber
WA
May 18, 2010 - 11:25pm PT
looks like a knocker - seriously.... blueschist perhaps?
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
May 18, 2010 - 11:36pm PT
I'm glad you asked that question. That's a steeply-dipping outcrop of late Miocene-Pliocene Neroly Fm, an andestic-rich, primarily fluvial deposit. Here are some close-up photos.

Planar cross-stratification in Neroly blue sandstone. The blue color is related to a reduced iron-rich authigenic montmorillonoid coating on dark mineral grains.

Well-rounded, primarily andestic conglomerate. The provenance of the andesitic cobbles is the Stanislaus volcanic center in the Sierra Foothills.

Measuring dip using a Brunton compass.
Gary Carpenter

climber
SF Bay Area
May 18, 2010 - 11:58pm PT
Same pattern in grasses can be noted on the Sunol grade
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
May 19, 2010 - 12:12am PT
Blue sandstones of Central California...

DOI: 10.1306/74D70BF5-2B21-11D7-8648000102C1865D
Genetic Relationship Among Tertiary Blue Sandstones in Central California
J. F. Lerbekmo
Journal of Sedimentary Research
Volume 31 (1961)

ABSTRACT

Pliocene sandstones with a striking bluish hue are prominent along the western base of the Sierra Nevada Range in the Mehrten Formation, and in the Coastal ranges of central California in the Tehama, Neroly, Cierbo, Purisima, San Joaquin, and Etchegoin formations. The color has previously been shown to be due to a thin authigenic montmorillonoid coating on the dark-colored sand grains. These coated sandstones have in common a preponderance of andesitic detritus and a high degree of permeability. Interbedded coated and uncoated sandstones occur as a result of differing degrees of permeability, or, alternate derivation from andesitic and non-andesitic source rocks. Compositional and cross-stratification studies indicate that andesitic sandstones of the Mehrten, Etchegoin, and San Joaquin formations were derived from the Sierra Nevada; those of the Cierbo and Neroly formations, in addition to a major source in the Sierra Nevada, probably had some contribution from the Coast Ranges; the Tehama sediments were derived from the Coast Ranges; and the Purisima blue sandstones may have been derived from either Coast Range of Sierran effusive rocks to the east.
dipper

climber
Topic Author's Reply - Aug 9, 2010 - 09:01pm PT
Minerals and other rock hounds,

I was in the area described in my post #205 of this thread and came across what you see in the following images.

The dark, in the dark and light alternating samples is a fine powder ( though hard to touch) stuff that has precipitated out of the main mass. Both light and dark are hard and course to the touch, like 40-grit sandpaper.

Am told that this area includes a "salt-lick" used by local sheep.

What say ye about these minerals, Minerals?

Thanks in advance.



Image 1




Image 2




Image 3




Image 4



Image 5





Image 6




Image 7
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Aug 9, 2010 - 09:28pm PT
Dipper: your initial post was from the Pt Reyes area...these photos look like they're from the East side of the Sierras.

Looks like metamorphic rocks and since they're layered their origin is probably sedimentary or volcanic. So meta-sedimentary or meta-volcanic rocks. Looks like some chemical alteration, so there could be contact metamorphism. Based on the rhythmic bedding ~ 1 to 5 inches in thickness?, with alternating dark thin layers & coarser, quartz-rich? layers, it looks like episodic deposition in a distal facies of an alluvial or submarine fan or delta, where quartz-rich sediments or rhyolitic volcaniclastics are being deposited. That's my WAG.
dipper

climber
Topic Author's Reply - Aug 9, 2010 - 09:34pm PT
My Bad TT,

I changed it to say post #205.

Thanks for the WAG, and yes, eastern sierra.

I have two small samples if interest warrants seeing them up close and all.

Am told that the stuff sliding north out at Point Reyes was once down on the southern tip of the Sierra.

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Aug 10, 2010 - 12:07am PT
Dipper: I'll be interested to see if Minerals offers an interpretation. Can you take a close up photo of your sample and post it?

RE your question about Pt Reyes, here's a USGS animation that shows 30 million years of movement along the San Andreas fault and its predecessors. It is a compilation of an enormous inter-disciplinary data set including paleomagnetic data from the Transverse range (watch it rotate ~ 90 degrees clockwise) and the correlation of Pinnacles to the Neenatch Fm ~ 300 km to the south. You can see that Pt Reyes and Bodega Head, both composed of granite (Salinian Block), originate from the southern Sierras. The stripes off shore are sea floor magnetic anomalies.

http://earthquake.usgs.gov/monitoring/deformation/tectonics/western-na.mov
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Aug 10, 2010 - 01:02am PT
The location of right lateral slip along the western margin of the N American plate has migrated or "jumped" eastward (landward) with time. The previous incarnations of the modern San Andreas Fault are often referred to as the proto-SAF. You are correct that at about 12 mya, most of the right lateral slip is taking place mainly along the modern trace of the SAF.
dipper

climber
Topic Author's Reply - Aug 11, 2010 - 03:03pm PT
TT,

Very cool animation. Thanks for posting.

Here are two close-ups of one sample. Opposite sides of the same piece.

I am off to the mtns. for a few days. Thanks for any ideas you might share.







tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Aug 11, 2010 - 04:31pm PT
thanks for the close-ups...looks like quartz, feldspar (light minerals) and and the dark mineral is possibly an iron oxide maybe mangetite? so I'm guessing some kind of layered quartz-rich igneous rock

I'm curious what Minerals interpretation will be.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Aug 11, 2010 - 11:16pm PT
Geo bump
Minerals

Social climber
The Deli
Dec 9, 2010 - 02:22pm PT
Yeah, Geo Bump!

Hey, I missed your posts from August, Dipper, and apologize for not responding. Just stumbled across this while looking for an earlier post of mine, er... granites.

Tradster, I agree with your initial interpretation, on the previous page.

Dipper, it looks like banded marble – coarse-grained and recrystallized during contact metamorphism from the intrusion of the surrounding granitic magmas. Looks like another screen of at least two different metamorphic rock types in the outcrop photo (image 6).

The “salt-lick” reference would fit with a sedimentary protolith, no? The white mineral is calcite and the dark mineral is probably garnet or vesuvianite (idocrase) or some other common skarn mineral. In your post on the previous page, image 5 shows banding of the dark mineral and boudinage – the dark bands are broken up into segments. Boudinage forms during ductile deformation of the rock mass, due to the difference in mechanical competence of different materials/minerals. Image 4 shows the typical surface weathering texture of marble. Yup, 40-grit or coarser seems about right.

The close-up photos on this page definitely look like coarse-grained marble to me.

Here’s the real test… If the above photos are of a sample that you have collected, take a pocketknife to the white mineral and try to scratch it with the tip of the knife. If it scratches, it’s calcite. If it doesn’t scratch and the mineral is harder than the knife, then it’s quartz and/or feldspar.

Hope that helps! Cheers!


Now then… where are those Wild Dike photos…? That leucocratic septa has got to be a partial melt product…

Spider Savage

Mountain climber
SoCal
Dec 9, 2010 - 03:32pm PT
Dipper's last photo looks like calcite served up on matrix of decomposed granite. But the fellow above know's way more than I do.
dipper

climber
Topic Author's Reply - Dec 10, 2010 - 09:10pm PT
The image you reference depicts the Arch Rock area of Point Reyes National Seashore.
Jaybro

Social climber
Wolf City, Wyoming
Dec 11, 2010 - 12:09am PT
Wild Dykes?
Spider Savage

Mountain climber
SoCal
Dec 11, 2010 - 12:26am PT
Calcite is pretty mushy. And disappointing.

Quartz is nice.

Papa used to carry HCL in a little green bottle in the ashtray of his state of Idaho issued 1963 Scout. I've got a bottle in the garage but don't use it much.

Someone post another picture. This is getting boring.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Dec 11, 2010 - 12:42am PT
I usually scratch the white rock with a key or knife...if the metal comes off on the rock, it's usually quartz...if the rock is easily scratched by the metal, it's usually calcite

Here's Minerals in action describing the origin of Ladder Dikes

Jaybro...these are the wildest dikes I've seen in a long time

Deformed Cambrian Quartzite near May Lake

Here's an uplifted sea stack in Franciscan Melange on the Sonoma Coast near Jenner, CA. If you look closely, you can see a couple of olistostromes (exotic blocks found in submarine deposits resulting from slumping or gravity sliding)

Here's a closeup of the Green Schist olistostrome (dk green oval shaped block just below center)

here's a closeup of the Blue Schist olistostrome (just left of center)
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Dec 21, 2010 - 01:38am PT
geobump
dipper

climber
Topic Author's Reply - Dec 21, 2010 - 02:08am PT
Still have not scratched those earlier samples....


Check out the feature smack dab in the middle in the below image:




Now check out the up close and personal:


Reilly

Mountain climber
The Other Monrovia- CA
Dec 21, 2010 - 02:13am PT
TT, Nice shots of yer . . . . . . . . . . . . . . . . . . . purty choss.
But keep it up, I love it when ya talk dirty!

So Nat Geo had a show tonight on the world's biggest cave: Mt River Cave in
Vietnam. They couldn't figger out how it got so big until they realized it
was in fact a fault line through the massive homogeneous karst that got
eroded by the surface river. Pretty dam cool:

http://www.dancewithshadows.com/travel/hang-son-doong-photos.asp

http://hangsondoong.com/

http://channel.nationalgeographic.com/episode/world-s-biggest-cave-5171/Photos#tab-Photos/0

Doesn't this look fun? (probably does to PTPP)

I gotta say they went pretty berserk with their Hiltis - somewhat questionable style IMHO.
Spider Savage

Mountain climber
SoCal
Dec 21, 2010 - 04:40am PT
That cave in "Nam is pretty cool!

Dipper's feldspar blob above is fascinating. I picture that big chunk floating in the deep plastic half a billion years ago and wonder how and why.
ydpl8s

Trad climber
Santa Monica, California
Dec 21, 2010 - 11:43am PT
Marble? Did somebody say marble?

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Dec 21, 2010 - 04:09pm PT
dipper: very cool photo of what appears to be an aplite dike?

reminds me of this outcrop near the summit of Mt Whitney
Minerals

Social climber
The Deli
Dec 21, 2010 - 04:22pm PT
Wow! That’s some crazy looking rock, Dipper. Really neat. 3-D checkerboard!

Yeah, looks like it could be a pegmatite dike that is mostly, or all K-spar (orthoclase). You can see that there is a series of dikes in the second photo. The rock fractured along the dike, leaving the planar surface exposed. The checkerboard pattern may be a result of the cleavage angles in the K-spar, and formed as the rock fractured.

Another possibility is that the dikes are composed of aplite (fine-grained) and the complex fracture pattern within the dikes developed prior to the formation/fracturing of the planar surface that is now exposed. Granitic rock types of differing grain size behave differently under cooling and tectonic stresses – one rock type may be only slightly jointed while an adjacent type is completely chopped up.

It also looks like there is a little bit of modal layering (bands of light and dark minerals) in the bottom of the second photo, if you look closely. This is a somewhat common feature in granitic rocks.

The oldest granitic rock in the Sierra Nevada Batholith is about 220 million or so years old while the quartzite near May Lake in Tradster’s third photo above is about half a billion years old.


Edit: Didn’t see Tradster’s post before I posted but was thinking of that photo too. Cool stuff.
scuffy b

climber
Three feet higher
Dec 21, 2010 - 04:52pm PT
Are the roof pendants further south in the Sierra roughly the same age
as the May Lake/Snow Peak quartzites?

I have another question about those. In that new book we are told the
May Lake metamorphics migrated a long way from the South.
Were they formerly south of the big roof pendants?
Minerals

Social climber
The Deli
Dec 21, 2010 - 06:58pm PT
The metamorphic roof pendants of the Sierra vary in age. The quartzite at May Lake is related to the Zabriskie Quartzite in Death Valley and the Tapeats Sandstone in the Grand Canyon. The metavolcanic rocks in the Tioga Pass area are younger (Triassic and Jurassic) but the metasedimentary rocks in that area are closer in age to the quartzite at May Lake. I believe that the metavolcanic rocks of the Ritter Range pendant are Triassic as well (without bothering to check…).

The metasedimentary rocks at May Lake, Benson Lake, and Snow Lake, etc. (western margin of the Tuolumne Intrusive Suite), are all part of the Snow Lake block, a huge slice of Earth’s crust that was transported approximately 400 km northward along the Mojave-Snow Lake Fault. This fault was an intra-arc strike-slip fault that was active somewhere in the time frame between 148 Ma (Independence Dike Swarm age) and maybe 120 or 130 Ma (I forget the exact age of the granitic unit that cuts the fault…). All of the younger metamorphic rocks in the Tioga Pass area lie to the east of what was once the trace of the Mojave-Snow Lake Fault. The quartzite of the Snow Lake block was transported from the Mojave Desert area, so yes, these rocks were formerly south of the eastern roof pendants.

Here’s a quick little diagram, hoisted from the net:


An intra-arc strike-slip fault forms within an active magmatic arc (chain of volcanoes with granitic rock forming underneath) because plate convergence at the subduction zone/trench is not perpendicular, but oblique. The magmatic arc acts as a structural weakness within the crust and a strike-slip fault develops, in order to accommodate the oblique convergence forces at the trench. If it weren’t for oblique convergence at the trench, the quartzite at May Lake would still be sitting in the Mojave Desert area. Does that make sense?


Here’s an abstract on the Mojave-Snow Lake Fault from my professors:
http://www.agu.org/journals/ABS/1990/TC009i006p01609.shtml


Here’s a great resource for checking out more of the roof pendants in the Sierra:
http://geomaps.geosci.unc.edu/quads/quads.htm

Don’t pay attention to the Jurassic age of the metaseds on the western side of the Tuolumne Intrusive Suite (Tuolumne quad) – that age is incorrect. Many new interpretations have been made regarding the various rock units on these Sierra quads since they were published, so don’t take the maps as 100% correct. Science is always evolving.

scuffy b

climber
Three feet higher
Dec 21, 2010 - 07:07pm PT
Just the kind of answer I was hoping for. Thanks, I'll check those
links as well.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Dec 21, 2010 - 09:11pm PT
To add to the story that Minerals describes above see Regional Tectonic Map below from Dickinson's 2008 paper "Accretionary Mesozoic-Cenozoic expansion of the Cordilleran continental margin in California and adjacent Oregon." Geosphere 2008;4;329-353. The map is a snapshot from the Paleozoic-Mesozoic time boundary (~225 MYA) showing the Cordilleran miogeoclinal rocks (stippled orange, that includes the Zabriskie & May Lake Quartzites) offset along a regional left-lateral strike slip fault.

The line of truncation was oriented northwest-southeast at a high angle to the northeast-southwest trend of Paleozoic tectonic elements crossing Nevada (Dickinson, 2000), and is delineated in California by the eastern limit of subsequently accreted Mesozoic tectonic elements. The truncated continental margin that formed near the Paleozoic–Mesozoic time boundary became the locus for subsequent circ#m-Pacific subduction of seafloor beneath California (Hamilton,1969). The diverse post–Middle Triassic accretionary belts underlying about half the width of California accumulated sequentially against the truncated continental margin.

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Dec 22, 2010 - 05:25pm PT
Here is a chronostratigraphic chart showing the age relationships for accreted terrains in Central & Northern California, including roof pendants in the Sierrasn (Dickinson, 2008).


Here's a map showing the location of these terrains, including the May Lake Quartzite (Dickinson, 2008).

tenesmus

Trad climber
slc
Dec 22, 2010 - 06:26pm PT
I've seen checkerboards like that about 200 yards from this boulder problem. Its all red and black and chunky. fun stuff.



tenesmus

Trad climber
slc
Dec 22, 2010 - 06:37pm PT
There are loads and loads of dikes at this place. When they start to erode,the granite around them usually goes first and you are left with these cool cracks and/or features to climb. Combined with a nice creek in the spring, tall pinons and isolation, its my new favorite place.



tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Jan 21, 2011 - 01:48am PT
Angular unconformity between vertical Pre-Cambrian Uncompahgre Quartzite and flat lying Devonian Elbert Sandstone, Box Canyon, Ouray, Colorado
Minerals

Social climber
The Deli
Jan 11, 2012 - 08:48pm PT
Here’s to Nicolas Steno and historical geology on his birthday!

http://en.wikipedia.org/wiki/Nicolas_Steno

A little stratigraphy from today’s Google page:

scuffy b

climber
heading slowly NNW
Jan 12, 2012 - 11:25am PT
Happy Birthday, Steno!! What a badass the guy was.
Reilly

Mountain climber
The Other Monrovia- CA
Jan 12, 2012 - 11:58am PT
The north side of Fitzroy...
Dos XX

Trad climber
Los Angeles, CA
Jan 12, 2012 - 12:44pm PT
Very Gneiss, Reilly :-)
Shingle

climber
Jan 19, 2012 - 02:17pm PT
Road trip!

http://www.geosociety.org/fieldForums/12sierraNevada.htm
Bob Harrington

climber
Bishop, California
Jan 31, 2012 - 10:54pm PT

Nevadella?
Fritz

Trad climber
Choss Creek, ID
Jan 31, 2012 - 11:16pm PT
I can't identify "Bite" species, but I love to find those guys in old rock. Central Utah, a few in S. Idaho, & one I found at nearly 10,000 ft. in the Candadian Rockies.

Bites is fun!

(Trilobites)
Darwin

Trad climber
Seattle, WA
Jan 31, 2012 - 11:40pm PT
The trilobite is way cool and Reilly, thanks for that wild Fitzroy photo.


Tenesmus thanks for combining some climbing with the geology thread. Which direction from SLC does that lie?


But my real question: Specifically, are there caves in the large body of calciferous rock in the White Mountains NE of Bishop, CA? If not, is the explanation as simple as lack of water to erode/dissolve the rock? How often do large bodies of calciferous rocks exist without caves?
scuffy b

climber
heading slowly NNW
Feb 1, 2012 - 11:44am PT
High Quality, Bob!
Minerals

Social climber
The Deli
Feb 5, 2012 - 11:51pm PT
If you dig a square hole in a playa, 10 inches deep, and then pile up the dirt into a cone, which will disappear first – the hole or the cone?



Bob Harrington

climber
Bishop, California
Feb 6, 2012 - 01:13am PT
Looks like the hole is in the lead, but it might take a while for this race to finish. Is that Blackrock Desert?
Minerals

Social climber
The Deli
Feb 6, 2012 - 02:23am PT
Yes, the hole won the race, and eventually, there was just a slight bump where the cone sat. Now, there is nothing. But why did the hole win the race?

South of Black Rock – Granite Springs Valley, Bluewing/Adobe Flat.

That’s quite the fossil you’ve got there! Where’s Jaybro?

scuffy b

climber
heading slowly NNW
Feb 6, 2012 - 11:30am PT
The hole also has more opportunity to experience water-related effects.
BASE104

climber
An Oil Field
Feb 6, 2012 - 01:51pm PT
Minerals pokes his head back up! I thought we had lost you.

I need to yack with you about the work I am doing. Very exciting stuff if you are into rock mechanics and intense stratigraphy.
ydpl8s

Trad climber
Santa Monica, California
Feb 6, 2012 - 02:06pm PT
Send in these guys.

Bob Harrington

climber
Bishop, California
Feb 6, 2012 - 11:43pm PT
Here's my explanation of why the hole wins:

Cycles of precipitation, evaporation, and capillary rise result in the most soluble common salt, NaCl, on the surface of the playa. Dig the hole, then it rains enough to saturate the upper several feet of the playa with an Na-rich solution, which disperses the clays. Soil water flows into the hole, percolating through the clay or (more likely) through preferential flow paths along desiccation cracks, transporting the dispersed clay into the hole, filling it up. Alternatively, the precip picks up Na from the playa surface, runs off the playa surface, and ponds in the hole, and the Na-rich solution works on the walls of the hole, dispersing the clays, and the walls of the hole slough into the hole. Either way, the tendency toward clay dispersion works on filling up the hole.

The effect of precip on the pile is different. The rain is dilute, the clay remains flocculated, so the pile remains relatively intact.

So, how long did it take the hole and pile to disappear? There are a lot of circumstances that could change the outcome -- wind would (I think maybe) affect the pile more than the hole, the hydrology and chemistry of the playa would affect the process speculated about above, flooding of the playa might favor destruction of the pile through wave action, etc. ...

Here are a couple for more shots of the Inyo monster:



Minerals

Social climber
The Deli
Feb 8, 2012 - 12:14am PT
Wow, you guys are good!!! That’s way more than I would have come up with for an answer on why the hole wins the race. And I didn’t expect the photo to generate so much interest. I was looking through some photo files the other day and happen to run across that slide scan and had been meaning to post it here in the past because I like the photo and the contrast between the very small scale and the very large scale (hole and pile versus playa and mountains).

The hole was gone within a year or so but I think it took a couple or a few years for the pile to disappear. I’m not sure as I didn’t do much of a thorough follow-up and only checked on it a few times when I was passing through the area. So, it wasn’t really a true “experiment” – it was more of a spontaneous thought of… “hey, I’ll dig a hole for the heck of it and see what happens!” This was several years ago and I also spaced on taking a photo of the fresh hole.

Anyways, yeah, it seems that weather conditions would be a major factor and it would be interesting to see what would happen without any precipitation. After the first rain, it appears that a solid crust formed on the pile as it dried out (just like the playa surface), which made it much more resistant to wind erosion, whereas if it stayed dry, the finer silt and clay particles would be carried away by wind and destabilize the slopes of the pile. The hole would obviously remain longer without the presence of water.

I’m guessing that the white “ring” around the hole is a concentration of salt(s). Yes? The playa doesn’t flood too often and it looks like it wasn’t flooded between the time that the hole was dug and the photo was taken.

Here’s a photo of the playa in October of 2010, which was a very wet month, even in the desert. The edges of the playa had a “bathtub ring” of sorts and it looked like the entire playa surface had been covered in water not too many days before this photo was taken. As the playa began to dry out, mud cracks (or desiccation cracks, as mentioned above) formed. On this day, a slight wind was pushing the water across the playa and the fresh cracks were becoming submerged. Notice how the edges of the polygons curve upward and are exposed above the water level.




Oh!... speaking of playas… this reminds me… You know the famous “sliding rocks” of The Racetrack Playa in Death Valley, right? Anyone see or hear of this phenomenon occurring on other plays…?


“Do you dig many pits way out in the desert?”

OT… but… you mean like this one? :)




Back to really old dead things…
Bob, did you know that there are trilobite fossils in the area or did you just happen to stumble across that nice find while hiking? It looks like the rock was already split in two, judging by the little bit of sand on the surface. And I presume that it’s now proudly displayed on a bookshelf or something of the sort in your house? What’s the geologic rock unit?


BASE104 - email sent.


Bob Harrington

climber
Bishop, California
Feb 9, 2012 - 12:38am PT
The trilobite is from the Poleta Formation, annually trodden by many UC field camp students out in the Poleta Folds of Deep Springs Valley. We were just out hiking, my wife found it, then I found the other half after poking around for another while. Quite a find. Check out all the little bitty trilobites around the big one. We knew we were in the Cambrian, so such finds were a possibility.

Sliding rocks -- my "Racetrack Playa Rocks" file has a paper (Schumm, J. Sed. Pet., 26(3) 284-286, 1956) which discusses "playa stone tracks in California and Nevada..." The reference to Nevada is Clements, Wind-blown rocks and trails on Little Bonnie Claire Playa, Nye County, Nevada, J. Sed. Pet. 22, 182-186, 1952.

...OK, a little googling turned up a table in Paula Messina's disseration listing playas with reported sliding rocks, all in the Mojave.

Here's something to ponder



It's a road cut north of Mono Lake. Brush in upper left for scale.

What's with the pit? Is that a grave?!?
Reilly

Mountain climber
The Other Monrovia- CA
Feb 9, 2012 - 12:49pm PT
Bob, what a find!

Near the base of Fitzroy. A diamond in the rough.


BASE104

climber
An Oil Field
Feb 9, 2012 - 01:01pm PT
In sedimentary basin analysis, we call a hole "accomodation space."

It has a huge impact on how and why you get certain depositional environments of different sedimentary rocks.

Trust me. It goes far deeper than shales, sandstones, and limestones.

I do a lot of basinwide correlations of different rock sequences. Every day I yank up cross sections that are 50 or more miles long and correlate them. After a while, I have a total spiderweb of cross sections and can create a 3D model (easy on computers these days) of the basin. That, along with lithology and looking at the actual rocks for depositional environments, enables you to unravel 500 million years of history.

It is fun and not that hard. For me, anyway. I have been doing it for 25 years. I specialize in deltaic environments but have been working carbonates for the last 4 years.

Geology is so fun. You don't just look at the surface. You have to understand the 3D picture throughout the time that the rock records. Things also happen to rocks after they are deposited, so diagenisis is also an important part.

The general public has no appreciation for sedimentary rocks. They are super cool.
Bob Harrington

climber
Bishop, California
Feb 9, 2012 - 10:15pm PT
I want to be in a band called Accommodation Space.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 9, 2012 - 11:40pm PT
Here's another photo taken near Mono Lake of a similar feature to the one Bob Harrington posted above...


... soft sediment deformation triggered by a seismic event or deformation resulting from a glacier advancing into the lake??
Dr.Sprock

Boulder climber
I'm James Brown, Bi-atch!
Feb 9, 2012 - 11:44pm PT
have you guys heard of the lisping geologist?

Minerals

Social climber
The Deli
Feb 13, 2012 - 12:12am PT
Ah, Poleta. Jfailing posted a Google Earth photo of those folds in post #61 of this thread. Looks like an interesting area – I’ve driven by on 168 but never stopped to take a close look. Have you ever checked out the Papoose Flat Pluton and its contacts with the surrounding host rock? That’s been on my list for years.

Thanks for the references on sliding playa rocks. I found evidence on a playa here in Northern Nevada last spring, which is the first time that I’d seen this outside of the Racetrack Playa. Funny that I haven’t seen more evidence, given that I have been on a lot of playas here in Nevada. But maybe that’s because there are no rocks on ‘em in the first place! I mentioned what I had seen last spring to a professor friend and he thought it was interesting. Paula Messina and the Mojave… will keep that reference in mind and have a look.


Cool photo of the soft sed deformation. There is a photo in the new book, Geology Underfoot in Yosemite National Park, by Allen Glazner and Greg Stock, 2010, that is pretty much the same as your photo.

From the photo caption on page 251:

“Intensely contorted beds of basaltic Black Point tephra atop planar beds of the same material exposed at stop 1. The folds developed as the upper layers slumped while underwater – to the right in the photo. The boundary between the planar and folded layers is the slippery surface upon which the sliding took place. The white layer at the base of the tephra (foot level) is composed of a few inches of fine lake sediment (deposited at the bottom of Lake Russell) and is underlain by pinkish ash from the Mono Craters.”

And from the text on page 250:

“The amazing pear-shaped layers are folds that formed in the upper sandy layers when they slumped downhill, toward the center of the lake, during earthquakes. How did this happen? The cross-bedded sedimentary layers deposited on the lakebed were saturated and, being parallel to the lakebed, had a slight tilt toward the center of the lake. Earthquake shaking was enough of a jolt to cause some of the layers to slide downhill. The beds were folded and crumpled as they slid across the slippery surface of the beds below. Similar intensely folded layers of sediment occur in sand layers derived from other volcanoes around the lake, indicating that this process was common.”


Tradster, is that the same road cut? Looks very similar. Nice.


“Geology is so fun.”

Agreed! And it’s tough to ignore when we spend so much time outside having fun.


Oh… a grave? I suppose it’s a grave of sorts, for scrap metal from an abandoned ore mill. There is an old concrete foundation close to where the photo was taken, and a skarn mine a ways to the west. I thought I had found some more target material one morning, but after a little excavation exercise, it turned out to be more metal than I could manage. Darn. So I filled the hole in. But that’s not geology… Back to geology!

Minerals

Social climber
The Deli
Feb 13, 2012 - 12:17am PT
And…… a BUMP to bring back Weschrist and FortMental!!! They have certainly made positive contributions to threads like this one.

TGT

Social climber
So Cal
Feb 26, 2012 - 01:25am PT
Tucker has this in his collection, Don't know where it came from, but anyone have an idea of what the composition of the black inclusion in the quartz is?


It obviously grew as a crystal. Looks like it's octagonal
BASE104

Social climber
An Oil Field
Feb 26, 2012 - 04:07am PT
hmmm. Tourmaline often looks pretty black and crappy like that.

Hard to do geology from pictures, though.
Jaybro

Social climber
Wolf City, Wyoming
Feb 26, 2012 - 12:23pm PT
What minerals said.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Mar 18, 2012 - 11:48am PT
Outcrop of late Miocene Neroly Fm, andesite cobble-rich conglomerate, Altamont Hills, CA
This outcrop contains a long, 1 to 2 ft diameter, cylindrical cavity. At first I thought it was man made, but upon further inspection it appears natural.
Here is a photo of the feature looking back toward the face of the outcrop
Another view of this feature in the opposite direction taken with a flash light for illumination. The feature appears to extend 10s of feet.
Nearby feature, claystone-filled cavity...possible clue?

I'm puzzled as to how this long cylindrical feature formed...any ideas?

Grampa

Trad climber
OC in So Cal
Mar 18, 2012 - 12:19pm PT
If a block of soft material was covered during deposition of the conglomerate, then that soft material would erode faster than the harder conglomerate and leave a cavity.

Or aliens dug it out.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Mar 18, 2012 - 12:55pm PT
A long cylinder-shaped claystone rip up...the feature in the last photo is a remnant??
BASE104

Social climber
An Oil Field
Mar 18, 2012 - 02:11pm PT
I would say that it isn't a claystone. It is hard to tell from one little picture what the size of the clasts are in the conglomerate, but it looks to me like a boulder sized chunk is missing.

PM me whenever this thread wanders into sedimentary rocks.

edit: looked at the pictures and retract the above statement. I would love to look at it, but you have to follow the outcrop all around to really understand it.

The clasts are very well rounded, so they traveled a fair distance before being deposited in a high energy environment. That is conglomerate 101.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Mar 18, 2012 - 06:45pm PT
BASE104: interesting to think about the California paleogeography at the time these sediments were deposited. Very different than today. Probably like the Cascades.

The light grey lithology in the last photo of my post above is definitely claystone or silty claystone. The conglomerate contains predominately andesitic volcanic cobbles derived from the Sierra foothills. The Neroly Fm is roughly correlated to the Mehrten Fm in the Sierra foothills and also consists of andesite-rich fluvial and lahar deposits.

from a USGS open file report...
Tn Neroly Sandstone (Miocene) -- Blue, volcanic - rich, cross-
bedded sandstone and conglomerate; mainly nonmarine. The
Neroly Sandstone in this assemblage contains tuffs with K/Ar
ages of about 9.7 Ma (Black Diamond Park Tuff ) and 10-12 Ma
(Alves Tuff) (Sarna-Wojcicki, written communication, 1990).
Includes minor siltstone, locally mapped (Tns).

Some info on the Mehrten.
http://search.datapages.com/data/doi/10.1306/03B5AB06-16D1-11D7-8645000102C1865D

Here are a few more photos of the Neroly

Darwin

Trad climber
Seattle, WA
Jun 3, 2012 - 12:57pm PT



Y'all think there would be interest in a Caves and Karst thread? I know cavers have deep seated issues w.r.t. cave locations, and those issues make surfers look like open and welcoming come-share-my-break peaceniks. Nonetheless, the BC Limestone thread and others makes me think we could pull it off. I think I'm too timid to start the thread, though.

My real question that I asked some posts ago.

How often do large bodies of calciferous rocks exist without caves?
I'm thinking of the large body of calciferous rock in the White Mountains NE of Bishop, CA? I don't know if there are caves there, but I found no evidence of them in my brief camp out there. Is the explanation for no-caves as simple as lack of water to erode/dissolve the rock? nfw.

Darwin
Minerals

Social climber
The Deli
Jul 11, 2012 - 04:52pm PT

“Fe3O4”




Magnetite sand concentration derived from the weathering of Cathedral Peak Granodiorite, seen at the high-water mark along the Tuolumne River, just west of Tuolumne Meadow, summer solstice, 2010. Yes, you can pick it up with a magnet.

Minerals

Social climber
The Deli
Oct 2, 2012 - 07:58pm PT
Going for the Moho…

http://www.cnn.com/2012/10/01/tech/mantle-earth-drill-mission/index.html?hpt=hp_c1



(CNN) -- Humans have reached the moon and are planning to return samples from Mars, but when it comes to exploring the land deep beneath our feet, we have only scratched the surface of our planet.

This may be about to change with a $1 billion mission to drill 6 km (3.7 miles) beneath the seafloor to reach the Earth's mantle -- a 3000 km-thick layer of slowly deforming rock between the crust and the core which makes up the majority of our planet -- and bring back the first ever fresh samples.

It could help answer some of our biggest questions about the origins and evolution of Earth itself, with almost all of the sea floor and continents that make up the Earth´s surface originating from the mantle.

Geologists involved in the project are already comparing it to the Apollo Moon missions in terms of the value of the samples it could yield.

However, in order to reach those samples, the team of international scientists must first find a way to grind their way through ultra-hard rocks with 10 km-long (6.2 miles) drill pipes -- a technical challenge that one of the project co-leaders Damon Teagle, from the UK's University of Southampton calls, "the most challenging endeavor in the history of Earth science."

Their task will be all the more difficult for being conducted out in the middle of the ocean. It is here that the Earth´s crust is at its thinnest at around 6 km compared to as much as 60 km (37.3 miles) on land.

They have already identified three possible locations -- all in the Pacific Ocean -- where the ocean floor was formed at relatively fast spreading mid-ocean ridges, says Teagle.

The hole they will drill will be just 30 cm in width all the way from the ocean floor to inside the mantle -- a monumental engineering feat.

"It will be the equivalent of dangling a steel string the width of a human hair in the deep end of a swimming pool and inserting it into a thimble 1/10 mm wide on the bottom, and then drilling a few meters into the foundations," says Teagle.

To get to the mantle scientists will be relying on a purpose-built Japanese deep-sea drilling vessel called Chikyu, first launched in 2002 and capable of carrying 10 km of drilling pipes. It has already set a world-record for the deepest hole in scientific ocean drilling history, reaching 2.2 km into the seafloor.

What makes the task even more difficult is that, currently, the drill bits have a limited lifespan of between 50-60 hours before needing to be replaced, meaning drilling could take many years unless technology improves.

The first attempts to reach the Earth's mantle actually began back in the early 1960s. Dubbed "Project Mohole" after the Croatian meteorologist Andrija Mohorovicic who first discovered the boundary between the Earth's crust and mantle, a team of U.S. scientists managed to drill a few meters into the oceanic crust off Guadalupe Island in the eastern pacific. The achievement was recognized by a telegram from President John F. Kennedy but the project was closed down in 1966.

Since then, a Russian-project in the far north Kola Peninsula during the 1980s has taken over the record for the deepest borehole ever drilled, reaching 12 km into the earth's crust.

And In 2011, the oil giant Exxon Mobil recorded an even longer borehole at just over 12 km in eastern Russia. However, it wasn't drilled vertically downwards and only reached soft sedimentary rocks.

While neither of these record-drilling projects got close to the Earth's mantle, they did give the geologists leading the new project -- The Integrated Ocean Drilling Program (IODP) -- confidence that recent advances in drilling techniques have made their plans more feasible than ever before.

"Many of the technologies required are conventional deep-drilling technologies that are presently being used in the oil and gas industry," explain IODP geologists.

However, given the challenges and the likely cost of $1 billion plus, much of which still needs to be raised, skeptics may question the necessity of the mission.

For Teagle, reaching the Earth's mantle would provide a "legacy of fundamental scientific knowledge" and "inspire" future generations.

"I was giving a lecture to a group of 15-year-old high-school students recently and they [and their teachers] were fascinated by the technology and the thought that we could re-enter a hole just a few centimeters across with a drill string dangled from a ship in the open ocean 4 km above."

As well as the technical achievement of bringing back samples, the samples themselves will clarify many of the assumptions we have about how our planet works. Despite making up 68% of the Earth´s mass, Teagle says we only have a "reasonable" idea of what the mantle is made of and how it works.

"[The mantle] is the engine that drives how our planet works and why we have earthquakes and volcanoes and continents. We have the textbook cartoons but detailed knowledge is lacking," he says.

The Japanese government has already invested substantially in the project through the construction of Chikyu, with some scientists regarding the mission as the country's "moon project."

If Japanese support can be combined with other funding, Teagle says they could start drilling before the end of the decade, making it possible for humans to finally reach the Earth's mantle by the early 2020s.

BASE104

Social climber
An Oil Field
Oct 2, 2012 - 10:00pm PT
Minerals,

When I got my B.S., the last class you take is field geology, which in our case was at the OU Field Camp near Canon City, CO.

A lot of it was mapping structure and stratigraphy of sedimentary rocks, but we had a week of geophysics. This included doing gravity and magnetic surveys.

Well, we had worked an igneous area a couple of weeks before, and it had huge chunks of magnetite. I must have saved twenty pounds of the stuff. We had to divide up into small teams to use the magnetometer and gravity meter. My group of four was up second on the magnetic survey, which passed over a complicated ultramafic system.

I got the bright idea of tossing out about five pounds of magnetite at a couple of the mag survey flags that everyone took their readings at. Nobody caught on, but the area had been surveyed over and over each year and the prof knew the numbers. So 9/10 of the class had wild readings at two stations.

Nobody caught on. It just looks like a dark cobble, and that fit in well with the crap laying around.....

I was a little turd.

Also, that black crystal included into quartz above is 99% probability of tourmaline. I've seen the exact same stuff several times. Most tourmaline is not only not gem quality, it will fall apart in yer hands.
mechrist

Gym climber
South of Heaven
Apr 4, 2013 - 01:05pm PT
Interesting (but shallow) article about a study of the (deep) structure under CA

http://www.nature.com/news/how-the-west-was-built-1.12724
john hansen

climber
Apr 4, 2013 - 01:42pm PT
TT, this is probably out there but could that cylindrical hole be caused by a "tree mold"?

If a mud flow solidified around a tree stump and the stump eventually rots away.

They are fairly common when lava flows surround tree trunks. Could happen the same with a mud / slurry flow.
mechrist

Gym climber
South of Heaven
Apr 4, 2013 - 01:46pm PT
^ I'd say that is a good possibility, especially given the nature of the deposit. But I've seen similar things in grainite (not quite as long), which were clearly not formed by trees.
mechrist

Gym climber
South of Heaven
Oct 17, 2013 - 01:25pm PT
Man, searching soopertaco is a pain in the ass!

Probably a better thread for this, but I ain't spending the time to find it.

If you ever get a chance to play in the 3D simulator, you should. It is a blast.

http://www.isgtw.org/feature/3d-tectonic-modeling-answers-age-old-geology-question
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Oct 17, 2013 - 02:06pm PT
"Flat subduction" of the Farallon Plate is also evoked to explain mountain building during the Laramide Orogeny in the Rocky Mountains at the end of the Cretaceous.

http://1.bp.blogspot.com/-J2oEQPJQcVc/TlDdBjXBXdI/AAAAAAAAAc0/R9gVPko1Ct4/s1600/Farallon+subduction.jpg

http://www.gps.caltech.edu/~gurnis/Papers/2010_Liu_etal_NatureGeosci.pdf

john hansen: that's the best explanation I've heard so far. We find a lot of wood, including whole tree trunks, in the Neroly Fm that are petrified.

Here's one for Minerals..."cross bedding" in granite. Photo taken near Tenaya Lake.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Oct 17, 2013 - 03:00pm PT
My impression of the Basin & Range is a large-scale thermal dome extending from the Owens Valley to the Rocky Mts and underlain by a still active subducted oceanic ridge and melting Farallon Plate. Many of the regional extensional faults are reactivated thrust faults.

However, the complexity of B&R geology at the outcrop to 7.5 min quad scale can be overwhelming and has lead many geologists to drink.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Oct 17, 2013 - 04:04pm PT
not sure what the problem is...seems pretty straight forward ;-)

Grapevine Mts

Titus Cyn
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