Petrogenesis and tectonic settings of Proterozoic mafic magmatism from the northern Indian Shield and the Himalaya: possible role for interaction of mantle plume with the subcontinental lithospheric mantle

Abstract

Northern Indian Shield and the western Himalaya have an impressive record of mafic magmatism. The Aravalli Craton preserved 2.3 Ga komatiitic (picritic) and 2.1–1.8 Ga tholeiities. Gwalior and Betul belts preserved 2.1 and 1.5–1.2 Ga tholeiites, respectively. Western Himalaya has preserved 2.1–1.8 Ga tholeiites in Garhwal and Himachal regions. Studied rocks depict enriched rare earth elements, large ion lithophile elements and depleted high field strength elements. Whereas komatiites/picrites represent higher degrees of partial melting (c. 35–40%) at higher temperatures (c. 1500°C), tholeiites represent lower degrees of partial melting (c. 10%) at lower temperatures (c. 1200°C). Our results indicate interaction of mantle plume with variably enriched subcontinental lithospheric mantle sources, causing generation of these varied magmatic suites of rocks. Whereas the higher temperature komatiitic/picritic melts from the Aravalli region appear to have been generated closer to the plume head, the lower temperature tholeiitic melts from the shield region and western Himalaya were generated towards the plume margins. Different terrains of the study have undergone plume tectonics causing the development of the rift valleys. The majority of these developed into aulacogens, except for the Aravalli basin, which developed into deeper marine facies.