Provenance, tectonic setting and source-area weathering of Mesoproterozoic Kaimur Group, Vindhyan Supergroup, Central India
Meenal Mishra, Shinjana Sen
Abstract
The siliciclastic of the Upper Kaimur Group of the Vindhyan Supergroup in Central India have been geochemically studied in order to understand their provenance, paleoweathering conditions and tectonic conditions. A-CN-K (Al2O3-CaO-K2O) ternary diagram and chemical index of alteration (CIA) values suggest that the granitic source rocks underwent moderate to high degree of chemical weathering under moderate weathering conditions for an extended period of time, or under humid weathering for shorter periods of time. Similar CIA values in all textural types indicate that recycling processes homogenized the shale and sandstone compositions. Various geochemical discriminants and elemental ratios such as K2O/Na2O, Al2O3/TiO2, SiO2/MgO, La/Sc, Th/Sc, Zr/Sc, Th/Cr, [Gd/ Yb]N and pronounced negative Eu anomalies indicate the rocks to be the product of post-Archean, Proterozoic granitic source, with minor granodioritic input and substantial sediment recycling. The geochemical signatures corroborate their deposition in a subsiding foreland basin over Bundelkhand craton with provenance from south, south westerly Chotanagpur granite gneiss.