Lithosphere–asthenosphere interaction and carbonatite metasomatism in the genesis of Mesoproterozoic shoshonitic lamprophyres at Korakkodu, Wajrakarur kimberlite field, Eastern Dharwar Craton, southern India

Abstract

The spatial and temporal association between lamprophyres and kimberlites provides unique opportunities to explore their genetic relationships. This paper explores such a relationship by detailing mineralogical and geochemical aspects of Korakkodu lamprophyre dykes located within the well‐known Mesoproterozoic diamondiferous Wajrakarur Kimberlite field (WKF), towards the south‐western margin of Paleo–Mesoproterozoic Cuddapah Basin, Eastern Dharwar Craton, southern India. Mineralogy reveals that these dykes belong to calc‐alkaline variety of lamprophyres, but their geochemistry display mixed signals of both alkaline and calc‐alkaline lamprophyres. These lamprophyres are highly potassic, and their high Al2O3 and low‐TiO2 content implies a shoshonitic character. Low Mg#, Ni, and Cr concentration highlight their evolved nature. High (La/Yb)N and (Gd/Yb)N content is consistent with their derivation from low degrees of partial melting, whereas highly fractionated nature suggests the presence of garnet in their source. Absence of prominent Nb‐Ta anomaly implies to the dilution of lithospheric mantle source by melts rich in HFSEs and low La/Nb ratio compared to those of the calc‐alkaline island arc volcanics and suggests an asthenospheric overprint on lithospheric mantle source. Carbonatite metasomatism in the source region of these lamprophyres is apparent from conspicuously high‐Zr/Hf ratio, and the HFSE budget of these lamprophyres are principally controlled by the presence of phlogopite veins in their lithospheric source. An extremely heterogeneous and layered lithospheric mantle beneath Eastern Dharwar Craton has been inferred from the divergent genetic history of Mesoproterozoic lamprophyres and kimberlites in the Wajrakarur field.

Mineralogy and petrology of shoshonitic lamprophyre dykes from the Sivarampeta area, diamondiferous Wajrakarur kimberlite field, Eastern Dharwar craton, southern India

“…In this paper, mineral chemistry, bulk-rock, and radiogenic isotopic (Sr-Nd) geochemistry of the Sivarampeta lamprophyre (SPL) dykes are presented. Our aim is to explore the petrogenetic relationship, if any, between the hitherto studied lamprophyres and the co-spatial kimberlites of the WKF and compliments similar recent studies carried on calc-alkaline and/or shoshonitic lamprophyres at the Mudigubba, the Kadiri, the Korakkodu, and the Udiripikonda areas towards the western margin of the Cuddapah basin in the EDC (Pandey et al, 2017a(Pandey et al, , 2017b(Pandey et al, , 2018a(Pandey et al, , 2018bKhan et al, 2018;Raghuvanshi et al, 2019). We also attempt to understand the nature of mantle source of the Sivarampeta lamprophyres vis-à-vis recently identified three distinct lamprophyre source domains from the EDC (see Giri et al 2019).…”

“…Lamprophyres towards the western margin of the Cuddapah basin are relatively less studied compared to those from the Prakasam Alkaline Province at the eastern margin. Recent studies (Pandey et al, 2017a(Pandey et al, , 2017b(Pandey et al, , 2018a(Pandey et al, , 2018bRaghuvanshi et al 2019) on lamprophyres from the western margin of the Cuddapah basin have brought out involvement of three distinct mantle source domains in their genesis; (a) Domain I: represented by orogenic calc-alkaline and/or shoshonitic lamprophyres (e.g., Mudigubba, Udiripikonda, and Kadiri) derived from the SCLM, (b) Domain II: represented by orogenic-anorogenic, alkaline to calc-alkaline lamprophyres (e.g., Korakkodu) sampling mixed orogenic-anorogenic transitional source, and (iii) Domain III: represented by alkaline lamprophyres (e.g., Ankiraopalle) displaying a strong OIB type (asthenospheric) overprint on the SCLM source (see Giri et al 2019). The present study on the Sivarampeta lamprophyre dykes, located within diamondiferous Mesoproterozoic-Late Cretaceous Wajrakarur kimberlite field (WKF), assumes importance in this context.…”

Lamprophyres from the Indian shield: A review of their occurrence, petrology, tectonomagmatic significance and relationship with the Kimberlites and related rocks

“…3). An interesting finding is the presence of sagenitic texture in mica grains as a result of exsolution of 5-10 μm titanite needles, which is found in shoshonitic lamprophyres from other parts of the globe as well (Raghuvanshi et al, 2019). The elevated K 2 O content as compared to other lamprophyres from the EDC is due to the abundance of biotite.…”

Kimberlites, lamproites and lamprophyres from the Indian shield: Highlights of researches during 2016-2019

“…Petrology, bulk rock geochemistry and isotope geochemistry (Sr-Nd) studies of Mudigubba, Udiripikonda, Kadiri, Sivarampeta and Korakkodu lamprophyre dykes intruding the Peninsular Gneissic Complex, towards the western margin of the Cuddapah basin, have been reported from the Eastern Dharwar craton (Phani et al 2019, Raghuvanshi et al 2019, Pandey et al 2017a,b,c, 2018and Khan et al 2018. These lamprophyres, based on mineral chemistry and geochemistry, can be broadly grouped into belonging to two domains: (i) calc-alkaline lamprophyres (CALs) e.g., Mudigubba, Kadiri and Korakkodu and (ii) Shoshonitic lamprophytes e.g., Udinipikonda and Sivarampeta.…”