MULTIPHASE PHENAI MATA INTRUSIVE COMPLEX (DECCAN TRAP PROVINCE, INDIA) AND ITS ANALOGS IN THE SIBERIAN PLATFORM

Abstract

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 late 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 SiO2, TiO2, K2O and incompatible elements, being comparable with the basic rocks of paleorift zones in the Siberian Platform. Ogiginal 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 showsmonzonitoids of different types of occurrence syenite-porhyries of composite dikes of Chara-Sinsk Dike Swarm (CSDS). Similarity between the geodynamic setting of intrusions from CSDS (Vilyui Paleorift System) and PMIC (Narmada Rift Zone) as well as their geochemical resemblance suggest a common mechanism for generation of intermidiate and acidic rocks in toleiite-basalt magmatic series in ancient platforms.