Understanding the Neoproterozoic geodynamics of NW India: clues from tectonomagmatic studies of the Cryogenian Sindreth Basin at the eastern Malani Igneous Province

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The Sindreth basin in NW India can be regarded as archive for the multiphase pulses of bimodal volcano-plutonic melts representing a characteristic feature of the c. 20 Ma lasting Malani magmatic activity. The Neoproterozoic Malani Igneous Suite (MIS) in NW India along with analogous magmatic rocks from the adjoining Nagarparkar region in SE Pakistan can be classified as a Silicic Large Igneous Province (SLIP). This magmatic event includes predominant felsic volcanism, granite emplacement and felsic and mafic dyke intrusions. Felsic rocks have typical A-type affinity originated from high temperature melting with major crustal input. It has been evaluated during the first project phase that mafic volcanics and dykes of the bimodal suite show geochemical homogeneity and derivation from a depleted continental mantle source without significant crustal contamination. In this second project phase we will study the geochemical and radiogenic isotope composition of the mafic rocks in order to determine (1) their relation to the felsic MIS rocks, (2) the mantle source(s) of the dykes, (3) the possible contamination with crustal rocks of different tectonic blocks, and (4) the potential origin from melting of subcontinental lithospheric mantle that could be similar to the 65-million-year-old Deccan flood basalts. The geochemical study will thus provide insight into the origin of the large volumes of magmas of the MIS and on the structure and composition of the lithosphere at the boundary between the Marwar and Aravalli Cratons.