GeologyRocksQuartz and Olivine
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It's to do with CIPW
Thu, 11/01/2007 - 21:39It's to do with CIPW calculations I seem to recall. Remember the phase diagram might have SiO2, not quartz.
CIPW norm emphasizes the concentration of silica in relation to other oxides -> assign SiO2 first to feldspars, then, pyroxenes, and finally to quartz. In other words there has to be enough SiO2 free after all the other silicates have gotten their share. When you have a basic rock which contains olivine, it is undersaturated wrt SiO2 and hence no free SiO2 to make quartz.
I did this a long while ago, so someone might correct me 
That help?
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yea It did, although i just
Fri, 11/02/2007 - 01:38yea It did, although i just came across a phase diagram that shows a 2 liquidus state of quartz and olivine, so i guess they can exist together. they'll just keep re-reacting with each other until SiO2 becomes Cristabolite and olivine well olivine... i think i get it
man these phase diagrams are a pain.
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Quartz and Olivine
Submitted by Fulcrum on Wed, 10/31/2007 - 21:05.Is it possible?
I keep reading that these 2 minerals hate each other and will not form together, but looking at a few phase diagrams, i dont really see the evidence?