Petrology and geochemistry of Mesoproterozoic calc alkaline lamprophyres and Paleoproterozoic shoshonitic syenites from Eastern Dharwar Craton southern India

Abstract

The Dharwar Craton of the southern Indian shield is a mosaic of Archean granite-greenstone belts, divided into different crustal blocks differing in terms of the age of the basement, nature of the greenstone belts, and thickness of the crustal column (Ramakrishnan and Vaidyanadhan, 2008). The geodynamic evolution of the Eastern Dharwar Craton (EDC) is widely debated and the proposed models include (i) non-uniformitarian sagduction (Chardon et al., 1996, 1998), (ii) uniformitarian plate convergence (e.g., Chadwick et al., 1996, 2000; Jayananda et al., 2013), (iii) plume-model (Jayananda et al., 2000; Chardon et al., 2002) and (iv) a combination of both accretion and vertical tectonic processes (Naqvi et al., 2006). The signatures of these geodynamic processes are tapped in the sub-continental lithospheric mantle (SCLM) of the Dharwar Craton, which can be deciphered using deep mantle derived magmatic rocks like lamprophyres, kimberlites, lamproites, mafic dykes, etc as a tool. newlinePaleoproterozoic of the EDC include multiple distinct mafic dyke swarms ranging in age from 2.37 to 1.79 Ga (Samal et al., 2019) and ~2.21 Ga shoshonitic syenites of the Dancherla alkaline complex (Suresh et al., 2010), whereas the Mesoproterozoic of the EDC include ~1.5 Ga syenites from the Pulikonda alkaline complex (Suresh et al., 2010) and kimberlite, lamprophyre and lamproite provinces ranging in age from 1.4 to 0.96 Ga (see Chalapathi Rao et al., 2013 and references therein). Some of the interesting problems associated with the Neoarchean and Proterozoic geodynamics of the Eastern Dharwar Craton include (i) do the post-Archean magmatic rock record of the EDC tap a lithospheric mantle modified previously by subduction during Neoarchean accretion-related origin of the EDC?, (ii) how did the SCLM beneath the EDC evolve during Precambrian?, (iii) why is the Cuddapah Basin crescent shaped?, (iv) what caused a magmatic shutdown in the EDC for almost 400 million years (1.8-1.4 Ga)?, (v) what are the links between different alkaline provinces and newline2 newlinesupercontinent assemblies?, (vi) what triggered the kimberlite eruption during Grenvillian age?, and (vii) why is the WDC deprived of the alkaline rocks? This thesis attempts to answer some of these questions pose newline