Eastern Ghats Mobile Belt
The Eastern Ghats Belt (India) bears testimony to the assembly and dispersal of both the Columbia and Rodinia supercontinents, and possibly the formation of East Gondwana. The belt itself is a collage of different lithotectonic and isotopic domains, and therefore the petrological evolution of each domain is to be considered separately prior to the formation of the belt. In this paper, we present an updated review on the petrological and tectonic evolution of the different domains along with geochronological constraints. We develop tectonic models to show how different lithotectonic domains fit into supercontinent cycles in the Proterozoic period.
We present detailed and high-precision geochronological data on granulites occurring along the western boundary of the Eastern Ghats Belt, India. Age data on systematically sampled rocks coupled with geochemical observation have a potential to unravel the overprinted tectonothermal events operated during Precambrian time. Zircon U–Pb SHRIMP and monazite electron probe microanalysis (EPMA) U–Th–total Pb analyses, chemical zoning, microtextural investigation, and pressure–temperature calculations were carried out on samples of four different rock types. Inherited zircons from migmatitic quartzofeldspathic gneiss and mafic granulite yielded ages of approximately 2900–2350 Ma, representing an older crustal component. The age of granulite metamorphism recorded from charnockite and pelitic granulite ranges between approximately 950 and 930 Ma (from zircon and monazite). A possible decompression event from this area that occurred during Rodinia break-up is recorded from the Y-rich zones of monazite closely associated with porphyroblastic garnet in pelitic granulite and dates from approximately 800 to 750 Ma. Zircon grains of charnockite also yield a similar age. The youngest age of approximately 525–510 Ma documented from the monazite grains of migmatitic quartzofeldspathic gneiss and pelitic granulite, along with a spot age from zircon of migmatitic quartzofeldspathic gneiss, testifies to the final assembly of East Antarctica with cratonic India as a part of East Gondwana.