Institute of Disposal Research > Departments > Mineral resources > Research > Very large tuff-facies kimberlite in central India: Tokapal


The crater-facies kimberlite system at Tokapal occurs within the Late Proterozoic chemoclastic cover sequence of the Indravati Basin on the Archean to Meso-Proterozoic Bastar craton in central India. The pyroclastic lapilli tuffs  consist of pseudomorphs of olivine macrocrysts and juvenile lapilli set in a fine-grained talc-serpentine-carbonate matrix with locally abundant spinel and titanite. Garnet is rare. The inequigranular and locally bedded texture is largely preserved, although the olivine component has been completely destroyed. The multiple kimberlite system has about circular shape (2.5 km in diameter) and is probably the oldest and largest crater-facies kimberlite system known in the world. The satellite Bhejripadar system of similar petrographic and chemical characteristics is situated about 4 km to the northwest and has a few hundred meters of diameter.

Samples from both systems have mostly moderate degree of contamination (35-50 wt% SiO2, <4 wt% Al2O3) and Mg numbers of 82-89. The trace element patterns are typical of kimberlitic rocks (REE, Cr, Ni, Nb, Zr), with mobile elements strongly leached due to intense postmagmatic alteration and weathering (Ba, Sr, Rb, alkalis). In-situ U-Pb dating by laser-ablation quadrupole-based ICP-MS on autometasomatic titanite yielded an age of 620 ±30 Ma (2σ).The Nd isotope composition of εNd around -4.5 (T=620 Ma) is diagnostic of South African Group II kimberlite (orangeite). Limited microdiamond testing was unsuccessful so far. 

  • Mainkar D, Lehmann B, Haggerty SE (2004) The crater-facies kimberlite system of Tokapal, Bastar District, Chhattisgar, India. Lithos 76: 201-217
  • Lehmann B, Mainkar D, Belyatsky B (2006) The Tokapal crater-facies kimberlite system, Chhattisgarh, India: reconnaissance petrography and geochemistry. Journal of the Geological Society of India 68: 9-18
  • Lehmann B, Storey C, Mainkar D, Jeffries T (2007) In-situ U-Pb dating of titanite in the Tokapal-Bhejripadar kimberlite system, central India. In: Fareeduddin and RaoMS, eds, Kimberlites and related rocks of India. Journal Geological Society of India 69: 553-565
 

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