I am studying a sedimentary succession and DRX analysis indicate the presence of pirofilite. As I have no evidence of metamorphism I am thinking about the hydrothermal activity as the main cause for the pirofilite occurrence.
Dear A.J.C. Magalhães
it is very difficult to find literature sources about pyrophyllite in sediments. Hydrothermal or metamorphic origin Pyrophyllites are mostly trasportet to sediments.
Here are some papers. It can be useful for you!
Regards
Polla
1) http://www.sciencedirect.com/science/article/pii/0025322785900052
2) attached PDF file
Dear Mr. Magalhães,
pyrophyllite is the low-grade metamorphic successor of kaolinite-group minerals (> 400°C) and common to high-T hydrothermal alteration. I am currently studying pyrophyllite-bearing sediments in S America. The clay minerals are mainly detrital and preserved in the sediments as the pH is below pH 7. Please check my publications on APS minerals and kaolin, all of which are available on the Researchgate server.
Best regards
H.G.Dill
Dear AJC,
You say you have no evidence of metamorphism, however you have talc/pyrophillite, which is evidence of metamorphism! - metamorphism isn't always orogenies and plates smashing together, or igneous intrusions. Submarine spreading ridges commonly exhibit greenschist facies metamorphism in the basalts - mainly due to the hydrothermal activity. Talc is common in this (serpentinising) environment.
It stands to reason that if you had some deep muds or whatever that got hydrothermally altered, you'd find some metamorphic minerals.
Dan
Thank you Dan. Yes, you're correct. As I have pyrophyllite, I do have evidence of metamorphism.
Magal
Magal,
Sorry if that was a little basic, without a bit more info on the geological setting, it's hard to know how to pitch things on here!
Oi Magal!
Depois olhe no GEOBANK o mapa e nota explicativa da Folha Pará de Minas, aqui em Minas Gerais. Na área há um grande depósito de agalmatolito (rico em pirofilita), estudado pelo Prof. Antônio Romano (UFMG). Talvez haja informações úteis para você lá!
Grande abraço
Dear Dr. Magalhaes
In Argentina, in a Precambrian/Lower Paleozoic sedimentary sequence in Tandilia Sistem (Buenos Aires Province) at least 4 different levels with pyrophillite have been recongnized: There are serious discrepancies about the origin, some authors think that they are hydrothermal and other clastic (the basement is altered to phyrophillite in some parts). I am attaching two papers where you can find some references. In the paper of Poire et al, I highlighted the different outhors and source of phyrophyllite.
Hope these can help you
Sincerely
Dr. Fernanda Cravero
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