A new cache of Eoarchaean detrital zircons from the Singhbhum craton, eastern India and constraints on early Earth geodynamics

Bulusu Sreenivas , Sukanta Dey , Y.J. Bhaskar Rao , T. Vijaya Kumar , E.V.S.S.K. Babu, Ian S. Williams

We present U-Pb ages and Hf isotopic compositions of detrital zircon grains from w2.9 Ga old quartzites and magmatic zircon from a 3.505 Ga old dacite from the Iron Ore Group of the Singhbhum craton, eastern India. The detrital zircon grains range in age between 3.95 Ga and 2.91 Ga. Together with the recently reported Hadean, Eoarchean xenocrystic (up to 4.24 Ga) and modern detritus zircon grains from the Singhbhum craton, our results suggest that the Eoarchean detrital zircons represent crust generated by recycling of Hadean felsic crust formed at w4.3e4.2 Ga and w3.95 Ga. We observe a prominent shift in Hf isotope compositions at w3.6e3.5 Ga towards super-chondritic values, which signify an increased role for depleted mantle and the relevance of plate tectonics. The Paleo-, Mesoarchean zircon Hf isotopic record in the craton indicates crust generation involving the role of both depleted and enriched mantle sources. We infer a short-lived suprasubduction setting around w3.6e3.5 Ga followed by mantle plume activity during the Paleo-, Mesoarchean crust formation in the Singhbhum craton. The Singhbhum craton provides an additional repository for Earth’s oldest materials.

U-Pb concordia plot of zircons from dacite sample (SC-17-2). Symbol colors correspond to U concentration of zircons

 

Geoscience Frontiers 10 (2019) 1359e1370

https://doi.org/10.1016/j.gsf.2019.02.001