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

Abstract

Kimberlite field is an example of widespread Mesoproterozoic intracontinental magmatism. Recent studies have identified deep subcontinental lithospheric mantle as a source region of the kimberlite magmatism while timing, origin, and processes responsible for the generation of coeval lamprophyres remain poorly constrained. Here, we present and discuss new petrological and geochemical data for two lamprophyre dykes from the Wajrakarur kimberlite field and assess their petrogenetic relation to the kimberlite occurrences. Based on mineral compositional and whole‐rock geochemical characters, it is suggested that lamprophyres are formed through low degrees of partial melting of “enriched” lithospheric mantle that was modified and metasomatized by melts derived from recycled crust. This differs from geochemical imprints found in coeval kimberlites, where a crustal source component appears to be absent and is more consistent with rock derivation from “depleted” lithosphere which has experienced interaction with asthenosphere‐derived melts. An apparent lack of garnet in the mantle sources of lamprophyres is suggestive of melting at comparatively shallow depth (~100 km) relative to the kimberlites. Hence, these geochemically contrasting rocks, although have formed at the same time, are derived from vertically heterogeneous lithospheric mantle sources and can be explained through and linked with a thermal anomaly in the underlying convective asthenosphere. We suggest that the deeper mantle source region of the kimberlites was more pristine and devoid of subduction‐related signatures, whereas the shallower mantle source region of the lamprophyres seems to have preserved imprints of plate convergence and subduction associated with the evolution of the Dharwar Craton.

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).…”

“…(b) Geological map (afterNayak and Kudari, 1999) showing Sivarampeta lamprophyre confined to the Lattavaram cluster of Wajrakarur kimberlite field. Location of Ankiraopalli and Khaderpet lamprophyre are taken fromGiri et al (2019) andKhan et al (2018) respectively. Other fields are taken fromPandey et al (2017b).…”

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

“…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. The asthenospherization of lower reaches of SCLM by the carbonatitic melts from asthenosphere is the most plausible model to explain the mixed orogenic–anorogenic character in the shoshonitic lamprophyres from the WKF of EDC (Khan, Dongre, Viljoen, Li, & Le Roux, ; Pandey, Chalapathi Rao, Chakrabarti, et al, ). These sub‐lithopsheric carbonatite melts created enriched metasomes/veins rich in carbonates and phlogopite in the garnet lherzolite that was previously modified by fluid‐subduction metasomatism.…”

“…(b) Dy/ Yb vs. K/(Yb*1000) diagram (after Duggen et al, 2005) present geochemical modelling results. Non-modal fractional partial melting curves presented for garnet-lherzolite (Ol 0.6 Opx 0.2 Cpx 0.15 Grt 0.05 ), garnet phlogopite lherzolite (Ol 0.56 Opx 0.19 Cpx 0.14 Grt 0.05 Phl 0.06 ), and garnet amphibole lherzolite (Ol 0.56 Opx 0.24 Cpx 0.09 Sp 0.05 Amp 0.06 ) [Colour figure can be viewed at wileyonlinelibrary.com]mixed orogenic-anorogenic character in the shoshonitic lamprophyres from the WKF of EDC(Khan, Dongre, Viljoen, Li, & Le Roux, 2018;…”

Evolution of the Indian subcontinent: Introduction

“…A comparison of the mafic dykes with those of the eastern Dharwar Craton suggests the possibility of different mafic magmatic events in the WDC and EDC. Khan, Dongre, Viljoen, Li, and Le Roux (—this issue) focus on the petrogenetic history of lamprophyres, which are coeval with kimberlites in the Wajrakarur kimberlite field of the Dharwar Craton, considered to be of Mesoproterozoic age. They suggest that these geochemically contrasting rocks, although coeval, were derived from heterogeneous lithospheric mantle sources, which they link with a thermal anomaly in the underlying convective asthenosphere.…”