BIOTITE DEHYDRATION, PARTIAL MELTING, AND FLUID COMPOSITION: EXPERIMENTS IN THE SYSTEM KALO2-FEO-MGO-SIO2-H2O-CO2
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dc.contributor.author | Graphchikov A.A. | |
dc.contributor.author | Konilov A.N. | |
dc.contributor.author | Clemens J.D. | |
dc.date.accessioned | 2021-01-12T05:15:17Z | |
dc.date.available | 2021-01-12T05:15:17Z | |
dc.date.issued | 1999 | |
dc.identifier | https://elibrary.ru/item.asp?id=13322484 | |
dc.identifier.citation | American Mineralogist, 1999, , 1, 15-26 | |
dc.identifier.issn | 0003-004X | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/22733 | |
dc.description.abstract | Biotite solid-solutions are a significant H 2 O reservoir in the lithosphere, and the assemblage Bt+Opx+Kfs+Qtz is commonly used to estimate a H2O in high-grade metamorphic and magmatic rocks. Here we report experimental constraints on subsolidus mineral equilibria involving biotite and orthopyroxene in the system KAlO 2 -MgO-FeO-SiO 2 -H 2 O-CO 2 . Our experiments address the question of stability of biotite of a given X Fe in the assemblage Bt+Qtz+ or -Sa, or the stability of the assemblage Opx+Sa+ or -Qtz. Clemens (1993) and Clemens et al. (1997) concluded that CO 2 has no effect other than to lower a H2O and thereby raise the solidus T. Our data at X Fl H2O < extend these conclusions to encompass Fe-bearing systems more similar to natural rocks. From a comparison of experimental data and calculated isopleths of biotite composition in the divariant assemblage Bt+Opx+Kfs-Qtz+fluid, it appears that phlogopite-annite solid-solutions must be significantly non-ideal (at T<800 degrees C) or that enstatite-ferrosilite solid-solutions must have negative values for their Margules-type parameters. Ignoring these factors would result in any calculated a H2O values being too low. Although various models allow us to estimate X H2O in H 2 O-CO 2 fluids, we are still unable to use biotite equilibria to estimate a H2O accurately during high-grade metamorphism and magma crystallization. We also consider qualitatively the effects Fe-Mg biotite solid-solution on partial melting equilibria in fluid-poor (rock-dominated) systems in which hydration-dehydration reactions control the fluid composition. | |
dc.title | BIOTITE DEHYDRATION, PARTIAL MELTING, AND FLUID COMPOSITION: EXPERIMENTS IN THE SYSTEM KALO2-FEO-MGO-SIO2-H2O-CO2 | |
dc.type | Статья |
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