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golsen
Social climber
kennewick, wa
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Mar 16, 2005 - 02:39am PT
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thanks quickhiker. I get the cooling and I understand that it takes place at a gradient. I am missing the 120 degrees? That must be energy minimization on a molcular level? My PhD chemist girlfriend tells me that pentagons dont form at the moleculr level. These things are pretty uniform pentagons which I think would be 360/5 = 72 degrees. Oh well, they sure are fun to climb on.
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Haggis
Trad climber
Scotland
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Mar 16, 2005 - 09:57am PT
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nature:
ive left my notes at home
ill write a repy regarding the dolimite tomorrow when im back in my flat.
it has a lot to do with trace elements in melts and how they are very abundant in low melt fractions.
Rob
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nature
climber
Flagstaff, AZ
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Topic Author's Reply - Mar 16, 2005 - 10:29am PT
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bobh noted quartz monzogranite isn't on the ternary diagram so I assumed I had typed it wrong. I have not. So now maybe quckhikers statement regarding "not classifiable" has validity. Dibblee and others did map it as monzogranite. That must be the old nomenclature. quicktimer (or minerals or anyone) can you tell me how/where to look up classification of the monzogranite - how does it relate to the IUGS diagram?
Rob - looking forward to the explaination.
OK QH can I at least get out of you where you did your work? Was it UW?
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Lambone
Ice climber
Ashland, Or
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Mar 16, 2005 - 11:04am PT
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you won't hear from QH for a few days because he is out in the field...but yes, UW. he recently earned his phd....but he's too modest to tell anyone that. he'd probly rather take personal questions of line, send him an email.
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nature
climber
Flagstaff, AZ
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Topic Author's Reply - Mar 16, 2005 - 11:36am PT
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Lambone - thanks. I figured as much. I didn't mean to get personal with the questions and will email him directly. I do understand how asking about timing (length, etc.) might be a bit personal. I guess I really just wanted to know the level of eduction (I had guessed phd), where the degree was granted and the specialty. Seems right within context of this thread.
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Lambone
Ice climber
Ashland, Or
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Mar 16, 2005 - 11:38am PT
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yeah...all I know is he did most of his Thesis feild work in Toulomne! I can't pronounce or even come close to spelling his specialty, but I know it's more on the structural side.
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Haggis
Trad climber
Scotland
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Mar 17, 2005 - 10:36am PT
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i hope this makes sence
ok lets consider what happens when you just start to melt the mantle at high pressure.
starting with a undersaturated Basalt what happens if we remove SiO2?
Note I know and so should you that you cannot remove silica from the melt I will explain at the end just run with it
Your K2O + NaO : SiO2 ration increases
Basalt consists of Olivine Augite and Plag
Therefore the Plag starts to break down by losing the SiO2
This forms CaTs or CaTiTs as so CaAl2Si2O8 – SiO2 => CaAl2SiO6
It also forms Nepheline as so NaAlSi3O8 – 2SiO2 => NaAlSiO4
This produces Ol + Neph + TiAugite (Ti looks like Si so they replace each other very well)
Note there is no longer any Plag
Ok now hike the pressure up a bit more thus further reducing the SiO2 concentration
Your K2O + NaO : SiO2 ration increases again
Diopside now starts to loose SiO2
4CaMgSi2O6 – 3SiO2 => 2Ca2MgSi2O6 + MgSiO4
Diopside – silica reacts to form Melilite + Fosterite
thus we now have 2Ol + Mel + Neph
HOWEVER
this is where it gets really weird
you are now such low melt fractions that all of the incompatibles (Li Rb La’s Ac’s and volatiles like H2O and CO2) are concentrating in the melt and silica is not melting thus you start forming a lot of strange minerals
in the presence of lots of CO2 the system must stabiles and obey the laws of thermodynamics and le chatalites (SP?) principle
thus Fosterite + Diopside + carbon Dioxide => Dolomite + Ensatite
2Mg2SiO4 + CaMgSi2O6 + CO2 => CaMg(CO3)2 + 4MgSiO3
if you count the silica’s then they haven’t changed however you have not formed Mel which is a very unstable structure it has been replaced by dolomite also note that we are not taking about pheocryst phases and this stuff very rarly makes it to the surface becasue the mantel melts by decompression
ok now the hard bit
you cannot remove silica from the melt as its liquidus is higher than the liquiduses of the minerals above, thus you must melt to such a small degree that you start from Dolomite + Ensatite + Faylite + Neph and as you increase the melt you increase the silica and these react away to form undersat MORB
thus you start with what I have ended with and work backwards in real life its just better shown when you start with minerals that most people know and take for granted
in essence all really undersaturated Basalt starts life as this but when the melt increases it forms more stable species.
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Haggis
Trad climber
Scotland
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Mar 17, 2005 - 10:50am PT
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this may make things easier to grasp here
Rob
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Jaybro
Social climber
The West
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Mar 17, 2005 - 11:08am PT
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I concur that the NA intrusion is a mind blower. but, if it's not random what is it? Or, is the point just to ask the question?
The spider web intrusion that tells you where the east ledge rappells are is a mindblower, though it doesn't look like anything more than a vague spider web pattern. IMHO,It doesn't have to resemble anything else to be remarkable.
Vedauwoo, with it's hoodoos, Mushroom boulders and plethora of balanced rocks is one of the most mind blowingly surreal landscapes anywhere.
In both (and many more) cases it's not "random," Cause and affect and a nitpickingly tedious series of events lead to what's there.
I just don't buy the assertion of design, that the rejection of the 'Random' ( for lack of a better word) model seems to imply. Doesn't that lead to an unknowable infinite regression?
Gtanted, on some level it's all unkowable, anyway.
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Jaybro
Social climber
The West
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Mar 17, 2005 - 12:01pm PT
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Maybe a rough draft?
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nature
climber
Flagstaff, AZ
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Topic Author's Reply - Mar 17, 2005 - 01:53pm PT
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but the layer that looks like NA wasn't exposed until after the NA took shape.
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quickhiker
Trad climber
Seattle
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Mar 18, 2005 - 12:46am PT
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Haggis, I think you have a lot of neat ideas, and certainly have done a bit of chemistry to look at forumulae and not run screaming, and to have heard of Le Chatlier's principle. You opened a bit of a pandora's box, with a lot of neat, neat stuff in it. You may wish to look at a program called MELTS put together by Mark Ghiorso and Richard Sack (yes, that is his name). This program looks at equilibrium mineral assemblages in association with a melt. It doesn't deal with high silica melts (say dacite and above) very well, or metamorphic at all, but is exceptional at melting in the mantle. A few rules of thumb: increasing pressure will reduce melt fraction by stabilizing more compact crystal forms (volume/entropy tradeoff); dolomite is, sensu stricto, a sedimentary rock, the metamorphic changes you are referring to are part of a prgression towards pyroxenites, a very active field of research for those interested in the mantle; Le Chatliers principle is fundamentally based on energy arguments (G=H-TS is the simplest relation), and CO2 can happily exist separately in the mantle as a supercritical fluid (this is indirectly the source of DeBeers wealth as diamonds when you spawn kimberlites). A neat brother of Le Chatlier's principle that is relevant here is the somewhat obscure Darken relation.
The 120 degree geometric relationship is an energy minimization in a slightly different sense- more of a stress orientation thing. The intersections are at 120, though they can form columns of many shapes (pentagons, etc) depending on how the intersections are aligned. Individual fractures will curve into the stress field around other fractures. Mudcracks show the same thing, and the physics are actually pretty similar. You can actually figure out which cracks propagated first. The first ones will have nice 120 intersections. If you see a crack intersecting a line at 90, it happened later. Most of the time the crack will noticably curve in to be perpendicular to the straight edge. Repeat ad nausem and you can figure out the order of cracking. Not a great use of time, but something to do while you are waiting for people to catch up on a trail.
Since Lambone blew my cover... I did my PhD at UW which included field work in Tuolumne looking at mixing relationships between the various units and a second project at Chaos Crags in Lassen Volcanic National Park. Before that I did my BS and MS at UCSC doing structure/tectonics research. Fun stuff, but academia didn't leave nearly enough time for all the other things in life.
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Ed Hartouni
Trad climber
Livermore, CA
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Mar 18, 2005 - 02:10am PT
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Truely awesome to watch the Rock Jocks go at it here... makes me wish my brain were wired differently so I could actually do that science, geology.
As for randomness vs. purpose, our conscious existence results in a propensity for interperting that randomness as an intentional act or as some more purposeful event. It is one of the motives that drive scientific investigation as well as spiritual investigation. These are two path ways to enlightenment, I can't judge which is the more valid, but I do know which I have choosen.
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quickhiker
Trad climber
Seattle
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Mar 18, 2005 - 02:25am PT
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Yes. Who says those paths are separate? Chaos theory, non linear dynamics and related fields show that relatively moderate actions have impacts and can shift systems between stable states, into oscillations or into unstable trajectories (be it weather or populations or the chemistry of our bodies). In many ways, this is a back door to the holistic view of interconnectedness. Why not skirt the middle between the two? The divide between creative and emotive life and science is artificial, to me at least.
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Haggis
Trad climber
Scotland
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Mar 18, 2005 - 09:46am PT
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i am fortunate to have a really good lecturer and a basic understanding of chemistry
if you understand the diagram I posted above then you can do 90% of igneous geology with a little common sense.
Its only when we start raving on about carbonatites, kimberlites and other oddities that things start breaking at the edges.
I found out about a volcano called Ol Doingo Lengia in Tanzania today that erupts sodium carbonate how cool is that!! The lava flows are about 5cm think and are as runny as hot mud. They also dissolve in H2O so they don’t exist in the record.
Very strange
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nature
climber
Flagstaff, AZ
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Topic Author's Reply - Mar 18, 2005 - 09:48am PT
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A quick google search on your name and a lucky guess on the school and I had many web pages and all I needed to know. Though since you disclosed UCSC did you know a Rick Koehler while you were there?
Le Chatelier's priciple: "A system in equilibrium responds to stress in a manner that tends to relieve that stress".
G = H-TS
Gibbs = Enthalpy - Temp * Entropy
Speaking of screaming. Geochem flashbacks with Don Garlick. Gibbs always made me start to lose it. Of course, that equation is too simple (for Don). He wrote "if you memorize anything memorize this equation!"
dG =< VdP - SdT
yikes! (and that's not a equal to or greater than - dunno how ot properly get that symbol in but I'm sure the thermo folks know what it's suppose to be)
QH - maybe you missed this from above (where I wrote):
bobh noted quartz monzogranite isn't on the ternary diagram so I assumed I had typed it wrong. I have not. So now maybe quckhikers statement regarding "not classifiable" has validity. Dibblee and others did map it as monzogranite. That must be the old nomenclature. quicktimer (or minerals or anyone) can you tell me how/where to look up classification of the monzogranite - how does it relate to the IUGS diagram?
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bobh
climber
Bishop, California
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Mar 18, 2005 - 11:33am PT
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Nature, I've got an igneous petrology book from the 1940's somewhere, but I couldn't find it last night. I'll let you know if I find it.
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Minerals
Social climber
The Deli
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Mar 18, 2005 - 12:42pm PT
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I have been kinda out of touch with geology recently. All I can think about is dirt bikes. Racing every weekend, pimping out my new ride, and rebuilding the 500. But, I’ve got to start working on a poster for a GSA meeting at the end of April.
How’s it going, Glen? Good to hear that you have finished your PhD. Nice work! Will you be at the GSA meeting in San Jose? I’m working on ladder dikes hosted in metavolcanics by Steelhead Lake. Have you seen these? Here’s a picture of one of the ladder dikes by the Tuolumne River, as described by Reid (1993).
Anyone have any comments or suggestions for me? Have you seen the ‘Vortex’ on the SE flank of DAFF Dome? It’s a brain twister for sure!
Ladder Dike in Cathedral Peak granodiorite:
Glen, have you seen Walt’s dissertation or the paper in Geology that he wrote with Glazner and Coleman? Neat stuff.
Nature, I'm not sure about old nomenclature...
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Lambone
Ice climber
Ashland, Or
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Mar 18, 2005 - 01:03pm PT
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"Since Lambone blew my cover..."
sorry bro, but you should be prowd of your work at UW.
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Minerals
Social climber
The Deli
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Mar 18, 2005 - 02:16pm PT
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Proud. Prowd is the name of my route on LB.
Yeah, Glen, upper Tenaya Canyon. I remember some pics that you had on your site a while back. One section of the dikes has some pretty crazy mixing and mingling, eh? Hibbard thought someone could do a thesis on that one square meter of outcrop. Wild.
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