• Vikas Swarnkar

      Articles written in Journal of Earth System Science

    • Significance of assimilation and fractional crystallization (AFC) process in the generation of basaltic lava flows from Chhotaudepur area, Deccan Large Igneous Province, NW India

      Hari K R Vikas Swarnkar Manu Prasanth M P

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      Basaltic and basaltic andesitic flows have been identified from the Chhotaudepur area in the Deccan Large Igneous Province. The $\rm{SiO_{2}}$ content of these flows varies from 46.7 to 53.7 wt%. None of the samples have primary magma signatures as they exhibit low Mg# (0.42–0.68), Ni (4.8–33.4 ppm) andCr (33.08–143.06 ppm). Highly variable concentrations of the LILE [Rb (2–74 ppm), Ba (52–351 ppm), Cs (0.1–1 ppm) and Sr (273–745 ppm)] and relatively enriched LREE are also noticed. The coherent chondrite normalized REE diagram and primitive mantle normalized multi-element diagram suggests a consanguinity among the flows. Low $\rm{(Nb/Th)_{PM}}$ (0.30–1.09), high $\rm{(Th/Yb)_{PM}}$ (3.09–16.58) ratios and marked variations in Rb concentration (2.4–74.11 ppm) with variable La/Yb (5.5–23.7) ratios suggests that magmas in the Chhotaudepur region were assimilated by the crustal components. The elevated Th/Ta and La/Yb relation further indicate concurrent assimilation and fractional crystallization process was involved in the genesis of the flows. Assimilation and fractional crystallization modelling of the flows was carried out with 20% olivine, 25% clinopyroxene, 45% plagioclase and 10% titano-magnetite as fractionating minerals and upper continental crust as the assimilant. The results reveal that all the flows were modified by AFC process.

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