Malani Igneous Suite: Hot-Spot Magmatism and Cratonization of the Northern Part of the Indian Shield

Abstract

The trans-Aravalli igneous activity of Malani suite of western Rajasthan comprising non-orogenic peraluminous (Jalore and Tusham) to peralkaline (Siwana) granites with the cogenetic carapace of acid volcanics are characterized by ring structures. This alkaline (as opposed to subduction related calc-alkaline) magmatism which was due to hot-spot activity in the region is interpreted as the final tectono-magmatic event that marked the cratonization (stabilization) of the northern part of the Indian shield after the closure of Aravalli-Delhi orogenic cycles. The alkaline to subalkaline magmatism in the form of ring shaped intrusions of nepheline syenites, carbonatites and kimberlites is indicative of tensional environments which existed in the region prior to the emplacement of Malani suite of rocks. The nucleus of the Indo-Gangetic rift was probably formed some 1000 Ma ago. The cratonization was completed with the deposition of Vindhya Platform sediments. The scope of tin mineralization in the region is also discussed in the light of trace element data.