Le Breton, 1988 deshidratación de bt

Le Breton, 1988 deshidratación de bt - Contrib...

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Contrib Mineral Petrol (1988) 99:226-237 Contributions to Mineralogy and Petrology Springer-Verlag 1988 Fluid-absent (dehydration) melting of biotite in metapelites in the early stages of crustal anatexis Nicole Le Breton* and Alan Bruce Thompson Departement fiir Erdwissenschaften, ETH-Zentrum, CH-8092 Zfirich, Switzerland Abstract. Experimental investigation of the fluid absent melting reaction biotite+plagioclase+A12SiOs+quartz~ garnet + K-feldspar + melt at 10 kbar, indicated that melt- ing began between 760 and 800~ and was extensive at 850 ~ C. This reaction apparently has a positive dP/dT at least up to 10 kbar, compared to a calculated backbending in a simplified system. Natural biotites are stabilised to higher dehydration melting temperatures probably by Ti. Consequently, metapelites undergo two-stages of fluid-ab- sent melting even in thickened, continental crust. The two stages firstly as muscovite, and secondly as biotite react, appear to persist to at least 17 kbar, depending upon biotite composition. This lies well within the stability field of kya- nite migmatites. Thus, complex petrogenetic grids can be computed from the little available data over a wide range of P-T-Xroek-XH20 conditions. Microprobe analyses indicate
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This note was uploaded on 03/19/2012 for the course GEOLOGY 6 taught by Professor Rm during the Spring '12 term at UNAM MX.

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