Subduction-related origin of eclogite xenoliths from the Wajrakarur kimberlite field, Eastern Dharwar craton, Southern India: Constraints from petrology and geochemistry

Petrogenesis of lamprophyres synchronous to kimberlites from the Wajrakarur kimberlite field: Implications for contrasting lithospheric mantle sources and geodynamic evolution of the eastern Dharwar Craton of southern India

“…Pyroxene barometry (Putirka, ), as applied to the UKL, shows a pressure range of 1.15–1.6 GPa (Pandey, Chalapathi Rao, Chakrabarti, et al, ), corresponding to a depth of pyroxene crystallization of ~60 km and consistent with a model of lamprophyre genesis at a depth of <100 km. In contrast, mantle xenoliths from the WKF kimberlitic intrusives commonly show pressures of equilibration >5 GPa (Dongre et al, ; Nehru & Reddy, ; Patel, Ravi, Thakur, Rao, & Subbarao, ). Furthermore, the presence of diamonds in many of the kimberlite intrusives of the WKF serves to confirm their derivation from depths >150 km consistent with a thick underlying mantle lithosphere at the time of their emplacement.…”

“…This supports a model of contribution of melts from a lithospheric mantle source that had undergone metasomatic enrichment. An earlier subduction‐related tectono‐metamorphic event which consolidated the eastern and western parts of the Dharwar Craton took place in the Neoarchean (Chadwick, Vasudev, Hegde, & Nutman, ; Dongre et al, ; Rogers, Kolb, Meyer, & Armstrong, ), which is also marked by the intrusion of the Closepet granite and its equivalents at ~2.511 Ga. Multiple convergence of Cratonic microblocks during Dharwar Craton assembly at the end of the Neoarchean, leaving behind the greenstone belts as zones of palaeo‐ocean closure, is also envisaged in a recent study (Santosh & Li, ).…”

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

“…Moreover, eclogitic source can also be ruled out since eclogite restite in mantle would suppress the HREEs in the melts in equilibrium with them alike the adakites, which is not observed in these shoshonitic lamprophyres (Table ). Again, there are no reports of carbonates in the eclogite xenoliths found in co‐spatial Wajrakarur kimberlites (Dongre et al, ; Patel et al, ). It is also clear that only carbonate metasomatism is incapable of enriching these rocks in Al 2 O 3 and HREEs.…”

“…Since the eclogite and mafic mantle xenoliths from the kimberlites, from the WKF, reveal equilibration of mineral phases at pressures more than 5 GPa and, therefore, suggesting a thickened mid‐Proterozoic lithosphere (~170 km) beneath EDC (Chalapathi Rao et al, ; Dongre et al, ; Ganguly & Bhattacharya, ; Nehru & Reddy, ; Patel et al, ; Patel et al, ), it is unlikely that the SCLM was eroded or delaminated. Also, the occurrence of diamonds in Wajrakarur kimberlites is consistent with their derivation from mantle below minimum diamond stability depth (~150 km) and argues against a SCLM delamination or erosion model.…”

“…Numerous deep mantle derived alkaline rocks such as lamprophyres, lamproites, kimberlites, and their entrained eclogitic xenoliths have been used as proxies to understand the nature and evolution of the SCLM beneath the Eastern Dharwar Craton (EDC) in the past decade or so (e.g., Chalapathi Rao, Gibson, Pyle, & Dickin, ; Chakrabarti, Basu, & Paul, ; Chalapathi Rao, Wu, Mitchell, Li, & Lehmann, ; Dongre, Jacob, & Stern, ; Pandey, Chalapathi Rao, Pandit, et al, ; Pandey, Chalapathi Rao, Chakrabarti, et al, ; Patel, Thakur, Rao, & Subbarao, ; Patel et al, ). Recently, Pandey, Chalapathi Rao, Chakrabarti, et al () have shown that although the shoshonitic lamprophyres are coeval and cospatial with the Mesoproterozoic diamondiferous kimberlites from the Wajrakarur kimberlite field (WKF), they are not genetically related.…”