Home – Home – Jornals – Russian Geology and Geophysics 2002 number 10

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 Narmadan Rift Zone. It is made up chiefly of trap-intruding layered gabbros and related quartz monzonites. These both rocks are intruded by dikes of basites of tholeiite composition. The gabbroids are rich in Mg and poor in K. The final-stage basites are distinguished by higher contents of SiO₂, TiO₂, K₂O, and incompatible elements and are comparable with basites of paleorift zones of the Siberian Platform.
Original material was used to compare differentiates of tholeiite series from two largest provinces of manifestation of basaltic magmatism of ancient platforms: Deccan and Siberia. 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-Sin' 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 silicic rocks in tholeiite-basalt magmatic series on ancient platforms.