...they enjoy it.
Don't believe me? Then ask this muscovite, staurolite, and sillimanite, which have had the pleasure of growing in the space where an andalusite crystal has pulled apart:
Image with labels:
And a little explanation. Andalusite is one variety of aluminum silicate (Al2SiO5). There are three minerals with the same chemical composition: andalusite, sillimanite, and kyanite. They're stable at different temperature and pressures - andalusite is stable where it's hot at shallow depths (and is typically found in sediments that have been baked by the intrusion of magma); kyanite is found at higher pressures (that is, deeper in the crust); sillimanite is found at the highest temperatures (including in rocks that nearly melted). This rock tells a story: it was heated at shallow depths, and then was stretch while it was heated (and, I think, buried a little more).
(Elli, this is from Gallup Mills again. I'm working on probe data. The garnets have really cool zoning.)
Thursday, June 5, 2008
Rocks don't suffer deformation...
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3 comments:
Ha! I think that's a neat way to look at it. At first I thought you might be telling us not to use "suffer" when talking about rocks, and so I was thinking, "the poor, suffering rocks." - It was fun (and a pleasure!) to read your little twist.
Random thought: don't the staurolite crystals in the muscovite look like two eyes, a nose and a mouth???
I'll look forward to seeing the garnet zoning patterns :)
Elli - yes, that's exactly what made me want to post the image. :D It looks like a smile... or at least a grimace.
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