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Author Topic: What process created this?  (Read 16941 times)

Offline beem

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What process created this?
« on: 02/02/2009 01:26:11 »

I hope newbies are welcome to post New Topic...otherwise please ignore.
Discovered this superb website today...(and spent all day reading!)

Process?  Rock Type?




Thanks
Beem


 

Offline frethack

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What process created this?
« Reply #1 on: 02/02/2009 04:59:15 »
Welcome to the forum beem  ;D

You got me on this one.  Either stromatolites or algal mats with fenestral poring or some sort of gneiss with a preferentially weathered mineral(s).  Either way, Im pretty sure that Im wrong.
 

Offline DoctorBeaver

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What process created this?
« Reply #2 on: 02/02/2009 14:16:24 »
beem - welcome to TNS, and of course you can post. We are always pleased to see contributions from new members.

I'm not a geologist so I can't answer your quetion. I just dropped into this thread because I'm nosey.
 

Offline Mazurka

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What process created this?
« Reply #3 on: 02/02/2009 15:58:18 »
Looks like weathered metamorphic rock to me.  Grey stuff probably the result of hydrothermal fluids.  If nice little cubic crystals i would guess at Galena.
 

Offline Bass

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What process created this?
« Reply #4 on: 02/02/2009 18:29:14 »

I hope newbies are welcome to post New Topic...otherwise please ignore.
Discovered this superb website today...(and spent all day reading!)

Process?  Rock Type?




Thanks
Beem

Definitely high-grade metamorphic rock- note the isoclinal/chevron folds.  Probably a sheeted quartz vein before being so elegantly smashed and mashed.  Gray looks like some sort of coating from weathering- or is it part of the rock?  Is it metallic?  (My guess is not, since it doesn't show any signs of oxidation). 

 

Offline beem

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What process created this?
« Reply #5 on: 02/02/2009 19:05:02 »
Thanks for the welcome.
Nice to know geology dummies aren't taboo here.  ;D

Interesting replies..

Picture quality presents its own problem:  I'm so mesmerized by an interesting rock that my breath quickens, plus it's only a Sony Cybershot, so...a bit more info may be necessary.

This is the first of numerous rock pics I wish to show you, all from my 15 acres in the Okanagan of B.C. Canada.  A Geological Survey of Canada on BC's formations described my area as in between Chu Chua Formation with its accompanying grey phyllite and greenstone, and the Chilcotin Group containing basalt flows, ash, and volcaniclastic rocks.  Adjacent are pebble to boulder conglomerate, sedimentary breccia, sandstone, and rare shale and coal.  Also adjacent is Church's Penticton Group, the Dewdrop Flats Formation, with granite, gneiss, limestones and micaceous or argillaceous shists and slates.  Yet another area adjacent is known for basaltic andesite, biotite, hornblende and augite.

Numerous synclines mark the surrounding ridges.  And the "rare shale" includes a personal experience when I tried--eventually succeededing--in planting fifty 3-foot tall Douglas firs atop the shale outcrop whose width encompassed my entire planting area.   >:(  The outcrop was overlain by only 2 inches of soil.

The geological study concluded its report by adding "...an interesting area, deserving of further study."  (but not planting trees)  ;D

My uneducated guess was gneiss.
And wonder whether a vent could result in such chevron folding, or do vents generally...well...vent in basically a straight line?

So, as they say on TV, is that your final answer:D

Thanks for your opinions.
By finding this website, I know I've died and gone to heaven.  ;)
Next photo in 30 minutes....29.......28..... :)



 

Offline beem

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What process created this?
« Reply #6 on: 02/02/2009 19:27:37 »
Picture #2
Process? ID?

Sorry for large size (probably not allowed) ;) Oops, only reduced size transmitted.
Again, thanks for letting me harvest your knowledge.  ;D

A friend said this evidenced precipitous calcification.
I think he's dead wrong but don't know why ;D





 

Offline Bass

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What process created this?
« Reply #7 on: 02/02/2009 22:17:59 »
If that is calcite, my first thought would be solution collapse breccia, especially with the drusy texture.  In karst (caves) terrain, which I know exist in some of the limestones in the BC Okanagan area, as caves collapse the fragments are cemented with calcite, dolomite and more rarely quartz.

As to your first specimen- quartz veins generally form in fairly regular lines.  While these may wiggle a bit, or intersect other veins, it is highly unlikely that they form in folds (the one exception would be saddle reefs- but those tend to thicken noticeably in the hinges).  As to the process of formation, quartz veins were either injected into the country rock or formed during metamorphism by segregation of quartz, then were intensely folded during metamorphism.
 

Offline beem

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What process created this?
« Reply #8 on: 02/02/2009 23:15:38 »
Thank you!
My imagination is trying to create a vivid picture.

If only we could punch your text into graphics software to simulate the process.  [8D]
For visual people, like me.

Picture #3 Process?  ID?
At first glance, erosion by water. 
Couldn't be, though, as the effect shows relatively evenly all the way around.





 
 

Offline Bass

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What process created this?
« Reply #9 on: 03/02/2009 02:02:24 »
Looks like erosion by water - my guess is that this is a thinly bedded sandstone/siltstone that has been rounded by stream erosion.  Note how well rounded overall the rock is- the layers may contain thin laminations of mud or calcite that are more easily eroded, revealing the sedimentary layers.
 

Offline beem

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What process created this?
« Reply #10 on: 03/02/2009 03:38:44 »
Oh...oops [:I]

Would it then follow that Rock #3's little square bit was at the top in the shallow streambed, because straight edges vs rounded evidence less erosion?

All this talk about water (forgetting the glaciers for just a moment) is astounding, because the area now receives barely 13 inches rain annually.
These rocks are all being labelled tomorrow.  Thanks.

Please let me know when you've had enough of this ;D
 
Rock #4 Process?  ID?

Looks like it's been rusting inside?



 

Offline daveshorts

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What process created this?
« Reply #11 on: 03/02/2009 11:04:12 »
I might be wrong, but it looks like a piece of limestone or marble which has been crushed in a fault and then remineralised with something containing iron as water or mud flowed into the cracks. Although without adding acid to it is hard to be sure that it is limestone and not another white crystaline mineral.
 

Offline Bass

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What process created this?
« Reply #12 on: 03/02/2009 16:51:18 »
I agree with daveshorts.  Also, it would be helpful to provide a bit more information on your specimen, such as hardness, descriptions of any crystals, luster, etc.

The orange oxidation is typical of carbonates.  Most CaCO3 contains a bit of iron (siderite), when weathered tends to produce a distinctive orange-brown color. 
 

Offline beem

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What process created this?
« Reply #13 on: 03/02/2009 20:12:06 »
Damn...I lost my Preview copy to timing out. :(

Will learn procedure for Mohs hardness test this spring.
Recently joined local rockhound club.

The white covering on Rock #4 reminded me of a thin layer of hardened cracked cake icing, smooth and uniformly shiny, with no jagged pieces.

Rock #5  Process?  ID?


Grateful you're still interested in looking!  :)
 

Offline JimBob

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What process created this?
« Reply #14 on: 03/02/2009 23:54:21 »

I hope newbies are welcome to post New Topic...otherwise please ignore.
Discovered this superb website today...(and spent all day reading!)

Process?  Rock Type?




Thanks
Beem

Definitely high-grade metamorphic rock- note the isoclinal/chevron folds.  Probably a sheeted quartz vein before being so elegantly smashed and mashed.  Gray looks like some sort of coating from weathering- or is it part of the rock?  Is it metallic?  (My guess is not, since it doesn't show any signs of oxidation). 



This appears to be a cored volcanic bomb to me, deformed as it bounced around, partially solidified.
« Last Edit: 04/02/2009 00:00:03 by JimBob »
 

Offline JimBob

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What process created this?
« Reply #15 on: 04/02/2009 00:01:00 »
Looks like erosion by water - my guess is that this is a thinly bedded sandstone/siltstone that has been rounded by stream erosion.  Note how well rounded overall the rock is- the layers may contain thin laminations of mud or calcite that are more easily eroded, revealing the sedimentary layers.

agreed
 

Offline JimBob

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What process created this?
« Reply #16 on: 04/02/2009 00:02:57 »
Oh...oops [:I]

Would it then follow that Rock #3's little square bit was at the top in the shallow streambed, because straight edges vs rounded evidence less erosion?

All this talk about water (forgetting the glaciers for just a moment) is astounding, because the area now receives barely 13 inches rain annually.
These rocks are all being labelled tomorrow.  Thanks.

Please let me know when you've had enough of this ;D
 
Rock #4 Process?  ID?

Looks like it's been rusting inside?





Oh, Oh, someone get Bass into his chains.! This is his favorite rock - a breccia. He will surely give the lecture on this specimen.
 

Offline JimBob

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What process created this?
« Reply #17 on: 04/02/2009 00:04:56 »
Damn...I lost my Preview copy to timing out. :(

Will learn procedure for Mohs hardness test this spring.
Recently joined local rockhound club.

The white covering on Rock #4 reminded me of a thin layer of hardened cracked cake icing, smooth and uniformly shiny, with no jagged pieces.

Rock #5  Process?  ID?


Grateful you're still interested in looking!  :)

Hydrothermal vein rose quartz.
 

Offline beem

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What process created this?
« Reply #18 on: 04/02/2009 01:11:43 »
Quote
cored volcanic bomb
re Rock #1.
If your reply means the same as Bass' high-grade metamorphic, then you agree.

Re Rock #4 your reply, Breccia, a Google Image result shows so many different-looking rocks, presumably all formed by the same ? process?
The picture elicited no (apparent) excitement from Bass  ;D
He's likely exhausted from this exercise  [^]

Thanks JimBob for comments and ID'ing #5.

To myself Do I dare post another picture...yes, until they say ENOUGH

Rock #6  Process?  ID?
(this one's my favorite):


Thanks for looking!

After posting this, I discovered and read What is this and why all the layers?.
So...I know Rock #6 is NOT a Schist, but a Gneiss.

There's no smiley for patting myself on the back...
« Last Edit: 04/02/2009 01:25:52 by beem »
 

Offline frethack

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What process created this?
« Reply #19 on: 04/02/2009 03:27:25 »
Is the limestone breccia tectonically formed or is it from solution collapse?
 

Offline beem

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What process created this?
« Reply #20 on: 04/02/2009 04:20:02 »
oh, sure, frethack...the moment I get up enough courage to guess...er...a...draw upon what I've learned here, you hit me with a question that'll put me back where I belong...among the uninitiated   :D :D

Answer:  (drumroll) tectonic.

I'll answer your next question before you can pose it... [^]
Because of the red stuff in there.
More why:  The red stuff entered during a heat episode while deep in the ground.

(OMG, somebody help me out of this hole I'm digging myself into.

End my misery by telling me what the red stuff is.
Hopefully not blobs from a dripping grease gun. ;D
 

 

Offline frethack

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What process created this?
« Reply #21 on: 04/02/2009 05:25:32 »
Sorry beem, I was being a bit vague.  I was actually referring to this pic:



I should have pasted the pic in my response...sorry bout that!
 

Offline beem

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What process created this?
« Reply #22 on: 04/02/2009 05:36:19 »
Oh!
Schist!
 [:I]
 

Offline Bass

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What process created this?
« Reply #23 on: 04/02/2009 06:33:04 »
Beem, you guessed right!! [:0]

Quote
Oh, Oh, someone get Bass into his chains.! This is his favorite rock - a breccia. He will surely give the lecture on this specimen.

And since JimBob asked so nicely...

Tectonic breccia- no doubt.  Note that the clasts are all the same material, and that there is little rotation with matching boundaries.

Solution collapse breccias typically contain a mix of clast types (but not always), and the clasts are obviously displaced- rotated, no matching clast boundaries, may be rounded, and are commonly coated with calcite rims or drusy calcite and/or quartz.

There are two obvious fault structures cutting the rock, one from the upper right to the lower left, and another from the upper left to the middle where it gets cut off by the first fault.
 

Offline beem

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What process created this?
« Reply #24 on: 04/02/2009 17:18:52 »
So #6 rock is a gneiss.
And the red intrusions?
low-grade garnet?  or?  [?]

#4 rock is a breccia...I still don't get that one.  ???
Once the snow's gone I'll locate it and try to remove all the white and orange stuff to locate the jagged broken pieces typical of breccia.

Thank you.


 

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What process created this?
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