期刊
JOURNAL OF THE GEOLOGICAL SOCIETY OF INDIA
卷 78, 期 6, 页码 501-509出版社
SPRINGER INDIA
DOI: 10.1007/s12594-011-0126-0
关键词
Orthopyroxene; Deccan Traps; Concurrent Assimilation and Fractional Crystallization; Gabbro; Phenai; Mata.
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 A degrees 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.
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