Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

K. R. Hari ¹, C. G. Nambiar ², K. Furuyama ³, Suneet Kumar Rai ¹

Affiliations
1 Govt. Arts and Science College, Durg - 491001, Chhattisgarh, IN
2 Dept. of Marine Geology and Geophysics, Cochin University of Science and Technology, Kochi - 682016, Kerala, IN
3 Dept. of Geosciences, Osaka City University, Osaka 558-8585, JP

Abstract

Chhaktalao area situated 25 km NE of Ambadongar, is characterised by six flows of Deccan Trap. Of these two are tholeiitic basalts, one picrite basalt and three basaltic andesites. These flows are intruded by east-west trending dolerite, olivine dolerite, lamprophyres and carbonate-rich dyke-like bodies. In this paper the genetic relation between the flows and the dykes (dolerite and olivine dolerite) are discussed. Trace element geochemistry suggests that crustal contamination is not significant and did not play any vital role in the evolution of the lava flows and dykes. The dolerite and olivine dolerite dykes and mafic members of the flows show similar trace element characteristics indicating a broad chemical affinity between these two magmatic phases.

Keywords

Deccan Trap, Flows and Dykes, Geochemistry, Petrogenesis, Madhya Pradesh.

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K. R. Hari ¹, M. Satish Kumar ², M. Santosh ³, Suneet Kumar Rai ¹

Affiliations
1 Government Arts and Science College, Durg, Madhya Pradesh 491 001, IN
2 Department of Geoscience, Osaka City University-559, JP
3 Centre for Earth Science Studies, P.B.No. 7250, Akkulam, Trivandrum - 695 018, IN

Abstract

Carbonate-rich rocks occur as E-W trending dyke-like bodies in the Deccan 'basalts at Chhaktalao area in the lower Narmada valley and show a structurally controlled mode of emplacement. Modal composition shows calcite as the dominent mineral (∼90%). Ankerite, apatite, altered olivine, augite and opaques account for the remaining percentage. Geochemically, these rocks show high CaO (>50%) with low SiO₂, TiO₂, FeO* and K₂O. Trace element concentrations are low compared to average carbonatites. Stable isotope studies show that δ¹³C(-1.74‰ to -2.8‰) and δ¹⁸O(+12.75‰ to +13.35‰) values do not compare with those of "primary igneous carbonatites" eventhough they fall within the wide range of "igneous carbonatites". These rocks can be considered only as carbonate-rich rocks and not as true carbonatites.

Keywords

Petrology, Carbonate-Rich Rocks, Stable Isotope, Nannada Valley, Madhya Pradesh.

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