I’m in the process of writing a paper for my intro geology class and I’m having a few problems. The topic seems easy enough…“Choose at least 5 minerals and describe what they show about igneous and metamorphic rock formation”. I’ve been searching the internet and geology textbooks and have found volumes of information, but none of it directly applies to my situation. I know I have to include texture, composition, etc to discribe various aspects of a rock, but with my limited knowledge I’ve been unable to put it all together. Any help would be GREATLY appriciated.
It has something to do with crystallization?
How long is this paper supposed to be? Are you a geology major, or is this just filling a “sciences” requirement?
I am a geophysicist, but I’m not going to write your paper for you either; you might want to search (you are familiar with Google?) for the rock cycle and take note of the conditions of formation within such of both igneous and metamorphic rocks. Pay heed to the environmental conditions, such as heat and pressure.
Thanks a lot for everyone’s help. I think I should clearify a few things…I wasn’t very clear in my OP. I definitely don’t want anyone to write the paper for me, I’m just having some trouble fitting all of this together. I guess I need resources outlining various observable traits. Like say what the abundance of a certain mineral says about the composition of the magma or protolith. For some reason I’m having serious problems relating my limited knowledge of minerals to the formation of rocks.
I’m just finishing up my science requirements…I had no idea I would have this much trouble with an intro course
For metamorphic rocks particularly, many minerals form only under very specific conditions. There are polymorphs with the same chemical composition but different crystal form, depending on temperature and pressure; for example andalusite, sillimanite and kyanite.
And to the rest of y’all, learn the difference between rocks and minerals.
OK 'babe, I’ll fire off the top of my head that a rock is a naturally occuring bound aggregate of minerals. And our OP is concerned with the minerals that compose the rocks of igneous or metamorphic origin.
He’s probably given up on us for the night before the paper’s due anyway.
Nope, I’m still here. Thanks a lot for all your responses…I really appriciate it. It’s a little late so you’ll have to excuse my writing. I think the best way to describe my problem (and from what I can tell the entire class’s problem) is to use an example: olivine. If I happen to find a rock, that I determine to be igneous, with a high concentration of olivine I can assume that it formed at a higher temperature than say amphibole (at least I believe I can assume this because as the melt cools the now forming olivine crystals will sink to the bottom). If the rock formed at lower temps, the olivine would have become unstable, yes? I guess I’m just seeing if I’m on the right track.
Yes, most of y’all (meaning, except for Geobabe, lieu, and the former beatle, Ringo), please learn the difference between rocks and minerals! It pains me!
I am a geologist, and like the other geologists and non-geologists here I’m not going to write your paper for you, but in referencing Bowen’s Reaction Series(*), you’ve answered your own question. Here’s the hint: every mineral in a rock is significant in that it says something about the conditions in which the rock formed, whether it’s pressure, temperature, oxygen fugacity, silica activity, or etc. Usually especially when combined with data from another mineral phase present.
(*)By the way, whilst in Boston last week for the GSA meeting, I picked up a copy of N.L. Bown and Crystallization-Differentiation: The Evolution of a Theory by Davis Young. It’s a history of Igneous Petrology! Who wants to read it next? Anyone? Anyone?
My esteemed colleague here has said what I would have had I not been about to be late for work this morning. Seriously. Your answer is to be found in the Bowen Series, Grasshopper.
Hey, it’s what us Hard-Rock Igneous Petrology types do best!
And if you really want to squeal, check out my soon-to-be-issued article in the Journal of Volcanology and Geothermal Research (volume 111, pages 155-182, I think; due to be released in December) on the origins of a quartz trachyte-rhyolite suite by combined crustal melting, magma mixing, and fractional crystallization.
Talk about squealing! Petrogenesis gets me every time…