Eastern Ghats Province
The Eastern Ghats province, located east of the Eastern Dharwar craton, consists mainly of high-grade igneous and metamorphic rocks, but the ages of many of the rocks are not well established. The province is elongate in a north-northeast direction, and the main folds and shear zones are generally oriented in this direction as well. The western and northern margin of the Eastern Ghats province is a major thrust fault that places the Eastern Ghats over the Eastern Dharwar craton. This fault, known as the sukinda thrust, corresponds to major changes in the density of the crust on either side, showing that it is a major structure. The Godavari rift cuts the center of the Eastern Ghats province, then extends across the coastline into the Bay of Bengal.
Rock types in the Eastern Ghats include several igneous suites and high-grade metamorphic rocks. These can be divided into six main rock associations:
• mafic schists, consisting of biotite, muscovite, and amphibole
• charnockites, containing quartz, feldspar, and hyperstene
• khondalites, including calc-silicates that represent strongly metamorphosed sedimentary rocks, and are now rich in garnet, silliman-ite, cordierite, and sapphirine
• mafic granulites, containing plagio-clase, clinopyroxene, orthopyroxene, and amphibole
• anorthosites, consisting of plagioclase and associated with gabbro, dunite, and chromite bearing serpentinite, some of which have been dated to be about 1.3 billion years old
• alkaline rocks, forming posttectonic plutons cutting the other rocks, some of which have yielded isotopic ages of around 1.3 billion years
All of the rocks in the Eastern Ghats were strongly deformed and metamorphosed in the mid-Protero-zoic, around 1.4 billion years ago, and some evidence supports a magmatic event around 1.6 billion years ago. Even though there is a paucity of precisely determined isotopic Archean ages from the Eastern Ghats, many of the rocks, especially the schist belts, are quite similar to rocks in the Eastern and Western Dharwar cratons, and many Indian geologists have suggested that they may likewise be Archean.
Evolution of the Eastern Ghats began with deposition of silty and muddy sediments, carbonates, and basalts that later metamorphosed into khondalites and calc-silicate rocks. Volcano-sedimentary rocks that were deposited in several locations along the western side of the Eastern Ghats were later metamorphosed into schist belts. An orogenic event in the Middle Proterozoic caused east-west shortening and deformed the strata into northeast striking folds and shear zones and was associated with the high-grade granulite facies metamorphism. Later folds reorient some of the older folds, and intrusion of alkaline magmas occurred around 1.3-1.4 billion years ago. Structures along the western margin of the belt and the highgrade metamorphism suggest that the deformation and metamorphism formed during a continent-continent collision. similarities between the Eastern Ghats and the southern Granulite terrane suggest that the metamorphic events in the two may be related to the same major continent-continent collision event.
Continue reading here: Bhandara Craton
Was this article helpful?