Carbonate xenoliths hosted by the Mesoproterozoic Siddanpalli Kimberlite Cluster (Eastern Dharwar craton): Implications for the geodynamic evolution of southern India and its diamond and uranium metallogenesis

A number of limestone and metasomatised carbonate xenoliths occur in the 1,090 Ma Siddanpalli kimberlite cluster, Raichur kimberlite Field, Eastern Dharwar craton, southern India. These xenoliths are inferred to have been derived from the carbonate horizons of the Kurnool (Palnad) and Bhima Proterozoic basins and provide evidence for a connection between these basins in the geological past. A revised Mesoproterozoic age is proposed for the Bhima and Kurnool (Palnad) basins based on this kimberlite association and is in agreement with similar proposals made recently for the Chattisgarh and Upper Vindhyan sediments in Central India. The observed Bhima–Kurnool interbasinal uplift may have been caused by: (1) extension- or plume-related mafic alkaline magmatism that included the emplacement of the southern Indian kimberlites at *1.1 Ga, (2) mantle plume-related doming of the peninsular India during the Cretaceous, or (3) Quaternary differential uplift in this region. It is not possible, with the currently available geological information to constrain the exact timing of this uplift. The deep erosion of primary diamond sources in the Raichur kimberlite Field in the upper reaches of the Krishna River caused by this uplift could be the elusive source of the alluvial diamonds of the Krishna valley. Mesoproterozoic sedimentary basins can host world class unconformity-type uranium deposits. In light of its inferred Mesoproterozoic age, a more detailed stratigraphic and metallogenic analysis of the Kurnool basin is suggested for uranium exploration

Tracking India within precambrian supercontinent cycles

The term supercontinent generally implies grouping of formerly dispersed continents and/or their fragments in a close packing accounting for about 75% of earth’s landmass in a given interval of geologic time. The assembly and disruption of supercontinents rely on plate tectonic processes, and therefore, much speculation is involved particularly considering the debates surrounding the applicability of differential plate motion, the key to plate tectonics during the early Precambrian. The presence of Precambrian orogenic belts in all major continents is often considered as the marker of ancient collisional or accretionary sutures, which provide us clues to the history of periodic assembly of ancient supercontinents. Testing of any model assembly/breakup depends on precise age data and paleomagnetic pole reconstruction. The record of dispersal of the continents and release of enormous stress lie in extensional geological features, such as rift valleys, regionally extensive flood basalts, granite-rhyolite terrane, anorthosite complexes, mafic dyke swarms, and remnants of ancient mid-oceanic ridges. Indian shield with extensive Precambrian rock records is known to bear signatures of the past supercontinents in a fragmentary manner. Vast tracts of Precambrian rocks exposed in peninsular India and in the Lesser Himalaya and the Shillong plateau further north and east provide valuable clues to global tectonic reconstructions and the geodynamics of the respective periods. The Indian shield is a mosaic of Archean cratonic nuclei surrounded by Proterozoic orogenic belts, which preserve the records of geologic events since the Paleoarchean/Eoarchean. Here we discuss the sojourn of the Indian plate from the Archean through Proterozoic, in light of available models for supercontinent assembly and breakup in the Precambrian. We also discuss the issues in constraining the configuration, which is mainly due to scanty exposures, lack of reliable paleomagnetic poles from different cratons, and their time of formation or amalgamation. In this chapter, we briefly review Precambrian geology of India to track her participation in the making of the supercontinents through time.Sarbani Patranabis-Deb, Dilip Saha, and M. Santos