Sengupta et al., 1999

Sengupta et al., 1999 - JOURNAL OF PETROLOGY VOLUME 40...

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JOURNAL OF PETROLOGY VOLUME 40 NUMBER 7 PAGES 1065–1087 1999 Ultra-high Temperature Metamorphism of Metapelitic Granulites from Kondapalle, Eastern Ghats Belt: Implications for the Indo-Antarctic Correlation P. SENGUPTA 1 ,J .SEN 1,3 , S. DASGUPTA 1 , M. RAITH 2 * , U. K. BHUI 1 AND J. EHL 2 1 DEPARTMENT OF GEOLOGICAL SCIENCES, JADAVPUR UNIVERSITY, CALCUTTA 700032, INDIA 2 MINERALOGISCH–PETROLOGISCHES INSTITUT, UNIVERSITA ¨ T BONN, POPPELSDORFER SCHLOSS, 53115 BONN, GERMANY 3 ATOMIC MINERAL DIVISION, GOVERNMENT OF INDIA, LALCHAND BASTI, SHILLONG 793011, INDIA RECEIVED FEBRUARY 1, 1998; REVISED TYPESCRIPT ACCEPTED JANUARY 8, 1999 A suite of quartz- and corundum-bearing metapelitic granulites, metamorphism occurred in the lower crust (>8 kbar). Reported intruded by layered gabbronorite–pyroxenite–anorthosite at Kon- U–Pb cooling ages of monazite and allanite from a late pegmatite dapalle, Eastern Ghats Belt, preserves a multitude of reaction suggest the UHT metamorphism to be older than 1600 Ma. The textures involving oxide and silicate minerals that attest to several deduced P T history and the absence of Grenvillian high-grade prograde and retrograde reactions. In the quartz-bearing associations, metamorphism in the study area provide important constraints on the reactions are: (a) biotite + sillimanite + quartz garnet the configuration of East Gondwana, in particular on the continuation + liquid; (b) garnet + sillimanite spinel ( + magnetite) + of the Napier–Rayner terrane boundary into the Eastern Ghats quartz; (c) Fe 2 TiO 4 + O 2 ferrian ilmenite + magnetite; (d) Belt. reversal of reaction (b); (e) Fe 2 O 3 -rich ilmenite + plagioclase + quartz Fe 2 O 3 -poor ilmenite + garnet + O 2 . Reactions in the corundum-bearing associations are: (f) spinel + biotite + sil- limanite garnet + liquid; (g) biotite + sillimanite garnet + Ti-rich spinel + corundum + liquid; (h) biotite + sillimanite KEY WORDS: metapelitic granulites; UHT metamorphism; Eastern Ghats garnet + corundum + liquid; (i) Fe 2 4 + FeAl 2 O 4 + Belt, India; Indo-Antarctic terrane assembly O 2 ferrian ilmenite + Fe 3 O 4 + Al 2 O 3 (in ilmenite); (j) garnet + corundum spinel + sillimanite. To examine the paragenetic evolution of the metapelitic granulites, a petrogenetic grid for the KFMASH system at high temperatures and pressures, involving INTRODUCTION quartz and corundum, was constructed. The sequence of inferred Detail petrological investigations over the last decade reactions documents an anticlockwise heating–cooling path. Re- have identified a small number of regional granulite facies integrated compositions of spinel (with >10 mol % Fe 2 4 ) and terranes that underwent UHT metamorphism (ultra- feldspars indicate ultra-high temperature (UHT) of metamorphism high temperature >950 ° C) similar to pelitic xenoliths in (>1000 ° C), comparable with the liquidus temperature of the basaltic magma [reviewed by Harley (1989, 1992), enclosing magmatic rocks. Crystallization pressures inferred for the Hensen & Harley (1990) and Dasgupta & Sengupta magmatic rocks and the pressure constraints imposed by the petro- (1995); references therein]. Thermal modelling of these
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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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Sengupta et al., 1999 - JOURNAL OF PETROLOGY VOLUME 40...

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