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Petrogenesis of Gabbro and Orthopyroxene Gabbro from the Phenai Mata Igneous Complex, Deccan Volcanic Province: Products of Concurrent Assimilation and Fractional Crystallization


Affiliations
1 Government V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India
2 Centre of Advance Study in Geology, Banaras Hindu University, Varanasi – 221 005, India
     

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We report the occurrence of orthopyroxene gabbro from the Phenai Mata Igneous Complex (containing thoeliitic and alkaline rocks) that occur within Deccan Traps. The P-T calculations based on two pyroxene thermometry vary from 8.5±1.0 kbar and 963±39 °C. These gabbroic rocks exhibit high Mg# (0.67 to 0.71). But their primary magma signature can be negated due to their high SiO2 ( > 50 wt %), low Ni (32-35 ppm) and Cr (105-182 ppm) contents. Further, simple fractional crystallization was not responsible for the modification of the magma. Modeling carried out using trace element concentrations revealed that concurrent assimilation and fractional crystallization (AFC) was responsible for the genesis of these rocks. Small pods of magma could have accumulated in the crustal portions and concurrent assimilation and fractional crystallization have taken place in the generation of gabbro and orthopyroxene gabbro in the present study area.

Keywords

Orthopyroxene, Deccan Traps, Concurrent Assimilation and Fractional Crystallization, Gabbro, Phenai Mata.
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  • Petrogenesis of Gabbro and Orthopyroxene Gabbro from the Phenai Mata Igneous Complex, Deccan Volcanic Province: Products of Concurrent Assimilation and Fractional Crystallization

Abstract Views: 351  |  PDF Views: 18

Authors

K. R. Hari
Government V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India
N. V. Chalapathi Rao
Centre of Advance Study in Geology, Banaras Hindu University, Varanasi – 221 005, India
Vikas Swarnkar
Government V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India

Abstract


We report the occurrence of orthopyroxene gabbro from the Phenai Mata Igneous Complex (containing thoeliitic and alkaline rocks) that occur within Deccan Traps. The P-T calculations based on two pyroxene thermometry vary from 8.5±1.0 kbar and 963±39 °C. These gabbroic rocks exhibit high Mg# (0.67 to 0.71). But their primary magma signature can be negated due to their high SiO2 ( > 50 wt %), low Ni (32-35 ppm) and Cr (105-182 ppm) contents. Further, simple fractional crystallization was not responsible for the modification of the magma. Modeling carried out using trace element concentrations revealed that concurrent assimilation and fractional crystallization (AFC) was responsible for the genesis of these rocks. Small pods of magma could have accumulated in the crustal portions and concurrent assimilation and fractional crystallization have taken place in the generation of gabbro and orthopyroxene gabbro in the present study area.

Keywords


Orthopyroxene, Deccan Traps, Concurrent Assimilation and Fractional Crystallization, Gabbro, Phenai Mata.

References