Evolution of ca. 2.5 Ga Dongargarh volcano-sedimentary Supergroup, Bastar craton, Central India: Constraints from zircon U-Pb geochronology, bulk-rock geochemistry and Hf-Nd isotope systematics

The amalgamation of five Precambrian protocontinent blocks [Singhbhum, Bastar, Dharwar, Aravalli and Bundelkhand] resulted in the present-day tectonic configuration of India. The Dongargarh Supergroup is a major volcano-sedimentary sequence in the Bastar craton, central India. For nearly six decades: (1) it was presumed that the extensive lava pile in the Dongargarh Supergroup has accumulated over a protracted duration of magmatic eruptions spanning ~1.1 Gyr; and (2) the geodynamic setting in which the volcanic sequences of the Dongargarh Supergroup have evolved, remained enigmatic.
In this study, the detrital zircon U-Pb depositional ages acquired for the three intercalated sedimentary units, in combination with, the geochemistry and Hf-Nd isotope systematics in the volcanic rocks, as such, does not provide any evidence of significantly prolonged magmatism in the Dongargarh Supergroup. Rather, the results suggest short-lived magmatic event(s) spanning few tens of million years around ca. 2.5 Ga. Further, the geochemical attributes taken together with the Hf-Nd isotope signatures provide a compelling evidence of magmatism at a continental margin involving the subduction of oceanic crust beneath the continental lithosphere resulting in an Andean-type magmatic arc.  Furthermore, the oldest concordant zircon yielded a U-Pb age of 3770 Ma. This evidently indicates the presence of Eoarchean crust in the Bastar craton, central India. 
For further reading the reader is referred to the web version of the paper published in Earth-Science Reviews https://doi.org/10.1016/j.earscirev.2018.11.014 external link

Corresponding Author: Tarun C. Khanna (khannangri@ngri.res.in) 


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