Petrogenesis of Mesoproterozoic kimberlites in the Chigicherla region, Eastern Dharwar craton, Southern India: Insights into the origin of small-volume, enriched-mantle derived melts and link to subduction and supercontinent cycle

Abstract

We present new mineralogical, elemental and U-Pb perovskite age data for diamondiferous intrusions from Chigicherla kimberlite cluster of the Eastern Dharwar craton (EDC) in southern India. These rocks display inequigranular textures and contain macrocrysts, and segregations of solidified melts which are interpreted to be magmaclasts. Mineralogical studies indicate that intrusions CC-1 and CC-2 show a similarity to Kaapvaal lamproites, while the other three intrusions (CC-3, CC-4, and CC-5) display characteristics indicative of true kimberlite nature. The whole rock major and trace element geochemistry, involving large-ion lithophile and high-field strength elements, supports this observation. The geochemical signatures resembling Ocean Island Basalts (OIB) and metasomatism of source regions by fluids/melts emanating from deep-sourced upwelling mantle are consistent across the Chigicherla intrusions, mirroring other kimberlite intrusions within the EDC. Perovskite dating revealed a ²⁰⁶Pb/²³⁸U age of 1110 ± 9.5 Ma for the CC-1 pipe and 1116 ± 14 Ma for the CC-3 pipe.

This new data enables us to study the genesis of the Chigicherla intrusions specifically and to propose a new geodynamic model for the eruption of kimberlites and lamproites in southern India in general. The eruptions of predominantly kimberlites between 1055 and 1153 Ma and lamproites between 1300 and 1400 Ma are attributed to processes such as prolonged subduction, lithospheric extension, and mantle return flow, considering the plate tectonic evolution of the EDC during the Mesoproterozoic.