Abstract
A suite of quartz- and corundum-bearing metapelitic granulites, intruded by layered gabbronorite-pyroxenite-anorthosite at Kondapalle, Eastern Ghats Belt, preserves a multitude of reaction textures involving oxide and silicate minerals that attest to several prograde and retrograde reactions. In the quartz-bearing associations, the reactions are: (a) biotite + sillimanite + quartz →garnet + liquid; (b) garnet + sillimanite →spinel (+ magnetite) + quartz; (c) Fe2TiO4 + O2 →ferrian ilmenite + magnetite; (d) reversal of reaction (b); (e) Fe2O3-rich ilmenite + plagioclase + quartz →Fe2O3-poor ilmenite + garnet + O2. Reactions in the corundum-bearing associations are: (f) spinel + biotite + sillimanite →garnet + liquid; (g) biotite + sillimanite →garnet + Ti-rich spinel + corundum + liquid; (h) biotite + sillimanite →garnet + corundum + liquid; (i) Fe2TiO4 + FeAl2O4 + O2 →ferrian ilmenite + Fe3O4 + Al2O3 (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 quartz and corundum, was constructed. The sequence of inferred reactions documents an anticlockwise heating-cooling path. Reintegrated compositions of spinel (with >10 mol % Fe2TiO4) and feldspars indicate ultra-high temperature (UHT) of metamorphism (>1000°C), comparable with the liquidus temperature of the enclosing magmatic rocks. Crystallization pressures inferred for the magmatic rocks and the pressure constraints imposed by the petrogenetic grid on the metapelite assemblages indicate that the emplacement of the igneous suite and the accompanying UHT metamorphism occurred in the lower crust (>8 kbar). Reported U-Pb cooling ages of monazite and allanite from a late pegmatite suggest the UHT metamorphism to be older than 1600 Ma. The deduced P-T history and the absence of Grenvillian high-grade metamorphism in the study area provide important constraints on the configuration of East Gondwana, in particular on the continuation of the Napier-Rayner terrane boundary into the Eastern Ghats Belt.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
