Circum-Indian craton-margin orogenic reactivation during ca. 800-700 Ma: Tectonometamorphic characterization

The Precambrian history of the Indian continent centers around several Archean cratonic nuclei, e.g. the Singhbhum Craton, the Bundelkhand Craton and the Aravalli Craton in the north; the Bastar Craton in the central-east, and the Dharwad Craton in the south. Apart from a group of less disturbed and unmetamorphosed Meso- to Neoproterozoic platformal sedimentary packages resting over deformed and metamorphosed Archean to Paleoproterozoic basement, several Neoproterozoic orogenic belts occur at the margins of these Archean cratonic blocks. These craton-margin orogenic belts are the areas of intense deformation and multiple phases of deep- to intermediate depth, and hence constitute the sites of major records of crustal-scale material recycling through plate movements. They occur on the east, south and west of the Archean cratonic clusters (conjugate north and south Indian cratonic blocks). Though major deep-crustal deformation and metamorphism in these craton-margin orogenic belts can be tracked mostly up to the earliest Neoproterozoic, exhumation-related reactivation seems to be more common in these belt around ca. 800–750 Ma. 

In this study, we shall highlight the east and west Indian marginal belts. We shall present the new data showing conditions of metamorphic pulses and their age from the rocks of the Mercara Shear Zone, marking the south-western boundary of the Archean (>3000 Ma) Dharwar craton. The results indicate at least four events; (1) ~2900 Ma; basin formation with supply from craton, (2) 2900–2700 Ma; age of prograde metamorphism, (3) 2700–2500 Ma, age of charnockite magmatism during Dharwar Orogeny with metamorphic peak, and (4) final reactivation at 830–730 Ma marking exhumation of deep crust during retrograde metamorphism along the crustal scale shear zone (stretching lineation and S-C fabric formation as last deformation event. We shall also review our group’s recent published data on the pressure-temperature-deformation-fluid-age histories during the orogenic reactivation of the western boundary, and the Chilka Domain of the northern Eastern Ghats Belt. Together we shall try to collate data showing the idea of a near-synchronous orogenic reactivation surrounding Indian cratonic cluster during middle to late Tonian Period with various preceding age gaps.