Formation and fragmentation of the Palaeoproterozoic supercontinent Columbia: evidence from the Eastern Ghats Granulite Belt, southeast India

摘要

Recognition of Palaeoproterozoic subduction-induced continental collision and Mesoproterozoic rifting within the Great Proterozoic Fold Belt (GIPFOB) of India supports the existence of Columbia. The Eastern Ghats Granulite Belt (EGGB) is an important component of the GIPFOB and a key player in models of the configuration of the supercontinent. The southern segment of the EGGB records widespread 1.85–1.7 Ga subduction-related arc magmatism and 1.5–1.35 Ga rift-zone igneous activity. The Kondapalli Layered Complex and associated felsic and mafic granulites show unambiguous subduction-related bulk-rock geochemistries and appear to represent deeply eroded remnants of a Palaeoproterozoic continental-margin magmatic arc. The Kandra Ophiolite Complex (KOC), containing a well-developed sheeted-dike complex and plagiogranite, characterizes new oceanic crust formed in a suprasubduction- zone environment. Internal structures, lithological associations, and bulk-rock compositions indicate that the KOC represents a Rocas Verdes-type continental backarc basin. Mesoproterozoic extension, initiated between 1.5 and 1.35 Ga, involved the intrusion of alkaline complexes + variegated mafic dikes and the development of large sedimentary basins. This rifting produced an outboard transitional-to-true oceanic crust paralleling the Palaeoproterozoic arc axis. Voluminous Palaeoproterozoic subduction-related and Mesoproterozoic rift-related magmatism within the EGGB provide strong evidence for global events that correlate with the assembly and break-up of Columbia.