Multiphase Phenai Mata intrusive complex (Deccan Trap province, India) and its analogs on the Siberian Platform

This paper reports new data on petrology and geochemistry of gabbroids and quartz monzonites from the multiphase Phenai Mata Intrusive Complex (PMIC). The complex is situated in the northwest of the Deccan Trap Province in the Narmada Rift Zone. It is made up chiefly of trap-intruding layered gabbros and related quartz monzonites, both intruded by dikes of basic rocks of tholeiite composition. The gabbroids are rich in Mg and poor in K. The final-stage basic rocks have higher contents of SiO (sub 2) , TiO (sub 2) , K (sub 2) O, and incompatible elements, being comparable with the basic rocks of paleorift zones of the Siberian Platform. Original material was used to compare tholeiitic-series differentiates of two largest provinces, Deccan and Siberia, where basalt magmatism of ancient platforms is displayed. Comparison of element distribution shows that monzonitoids of different types of occurrence have in general similar chemical composition and the PMIC rocks are very close to quartz syenite-porphyries of composite dikes of the Chara-Sinsk Dike Swarm (CSDS). Similarity between the geodynamic settings of intrusions from the CSDS (Vilyui Paleorift System) and the PMIC (Narmada Rift Zone) as well as their geochemical resemblance suggest a common mechanism for generation of intermediate and acidic rocks in tholeiite-basalt magmatic series on ancient platforms.