Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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Metamorphic-Metasomatic Fluids and Al, Si Order/Disorder of K-Rich Alkali Feldspars from Southern Indian High Grade Terrain


Affiliations
1 Division of Minerals, CSIRO, Clayton South,. Victoria 3169, Australia
2 Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore - 560 012, India
3 Department of Instrumentation, Indian Institute of Science, Bangalore - 560 012, India
     

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The structural state of K-feldspars in the quartzofeldspathic gneisses, charnockites, metapelites and pegmatites from the southern Karnataka, northern Tamil Nadu and southern Kerala high-grade regions of southern India has been characterized using petrographic and powder X-ray diffraction methods. The observed distribution pattern of structural state with a preponderance of disordered K-feldspar polymorphs in granulites compared to the ordered microclines in the amphibolite facies rocks is interpreted to reflect principally the varying H2O contents in the metamorphic-metasomatic fluids across metamorphic grade. The K-feldspars in the pegmatites of granitic derivation and in a pegmatite of inferred metamorphic origin also point to the important role of aqueous fluids in their structural state.

Keywords

X-ray Diffraction, Amphibolite Facies, Granulites, Metamorphic-Metasomatic Fluids.
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  • Metamorphic-Metasomatic Fluids and Al, Si Order/Disorder of K-Rich Alkali Feldspars from Southern Indian High Grade Terrain

Abstract Views: 213  |  PDF Views: 2

Authors

V. Swamy
Division of Minerals, CSIRO, Clayton South,. Victoria 3169, Australia
G. V. Anantha Iyer
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore - 560 012, India
A. G. Menon
Department of Instrumentation, Indian Institute of Science, Bangalore - 560 012, India

Abstract


The structural state of K-feldspars in the quartzofeldspathic gneisses, charnockites, metapelites and pegmatites from the southern Karnataka, northern Tamil Nadu and southern Kerala high-grade regions of southern India has been characterized using petrographic and powder X-ray diffraction methods. The observed distribution pattern of structural state with a preponderance of disordered K-feldspar polymorphs in granulites compared to the ordered microclines in the amphibolite facies rocks is interpreted to reflect principally the varying H2O contents in the metamorphic-metasomatic fluids across metamorphic grade. The K-feldspars in the pegmatites of granitic derivation and in a pegmatite of inferred metamorphic origin also point to the important role of aqueous fluids in their structural state.

Keywords


X-ray Diffraction, Amphibolite Facies, Granulites, Metamorphic-Metasomatic Fluids.