We study the recently discovered Mainpur Kimberlite Field on the Bastar craton in central India. Four of the so far six discovered diatreme-facies kimberlites are diamondiferous, and artisanal mining has yielded stones up to 200 ct. Drill core from the diamondiferous Behradih pipe consists of pelletal-textured and olivine macrocrystic diatreme facies kimberlite variably affected by talc-serpentine-chlorite-carbonate alteration. Crustal xenoliths of resorbed feldspar, granite, and dolerite are common. The rocks have C.I. ≥1.6, 40-43 wt% SiO2, <5 wt% Al2O3, and Mg numbers of 83-87. The trace element composition is typical of kimberlitic rocks and excludes a lamproitic affinity.

The pipes have surprisingly young 40Ar/39Ar whole rock and U–Pb perovskite ages around 65 million years. These ages overlap with the main phase of the Deccan ood basalt magmatism, and suggest a common tectonomagmatic control for both ood basalts and kimberlites. The occurrence of macrodiamonds in the pipes implies the presence of a thick subcratonic lithosphere at the Cretaceous/Tertiary boundary (>140 km), signicantly different from the present-day thickness of the Indian lithosphere. About one third of the Indian lithosphere was lost during or after the Deccan ood basalt event. The superfast northward motion of the Indian plate prior to the collision with Eurasia cannot be related to lithospheric thinning during the Gondwana break-up at 130 Ma, as previously thought. 


    • Lehmann B, Burgess R, Frei D, Belyatsky B, Mainkar D, Chalapathi Rao NV, Heaman LM (2010) Diamondiferous kimberlites in central India synchronous with Deccan flood basalts.
      Earth and Planetary Science Letters 290: 142-149

    • Mainkar D, Lehmann B (2007) The diamondiferous Behradih kimberlite pipe, Mainpur Kimberlite Field, Chhattisgarh, India: reconnaissance petrography and geochemistry.
      In: Fareeduddin and Rao MS, eds, Kimberlites and related rocks of India, Journal Geological Society of India 69: 547-552


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