Chapter 9 Palaeoarchaean–Mesoproterozoic sedimentation and tectonics along the west-northwestern margin of the Singhbhum Granite body, eastern India: a synthesis

Abstract

Abstract The Singhbhum Craton preserves large low-grade tracts of an extensive stratigraphic period in the Precambrian and therefore is of prime importance for studying the Earth's early evolutionary processes. An early ( c. 3.1 Ga) crustal stabilization followed by a long period ( c. 500 Ma) of high freeboard conditions has been postulated from the terrane in recent times. Tectonostratigraphic analyses of the supracrustal successions, carried out in the present study, from the west-northwestern margin of the Singhbhum Granite body in the craton identify a hitherto undetected Mesoarchaean shelf sequence among these supracrustal successions. In contrast to current thinking, the observations imply immediate development of a passive margin setting following the craton's early stabilization. The cratonic margin later succumbed to a major compression, resulting in successive emplacement of thrust sheets from the northern hinterland side that produced an intermingling of thrust slices of basement rocks and the deformed shelf and rift sequences. This later compressive episode not only involved a part of the Mesoproterozoic Kolhan Basin, but its effects are also manifest as a second deformation throughout the western Iron Ore Group belt. Involvement of the Kolhan Group in the deformation milieu constrains the timing of this orogeny to the Grenvillian ( c. 1.0 Ga).