Geochemical Constraints on the Petrogenesis of Tirodi Gneissic Complex (TGC) from Central India

The Tirodi Gneissic Complex (TGC) from central India represents part of the basement gneisses. The TGC comprises a combination of pink and grey granitic gneiss assemblages, and it is petrographically characterized by biotite-rich granite gneisses. The geochemistry and isotope (Rb–Sr) data set is used to constrain the petrogenesis of TGC granitoids and Precambrian crustal evolution. Previous geochemical results from the study area were not focused on the genesis and crustal evolution of these granitoids. The present contribution addresses these issues by using new geochemical and isotopic data sets. The studied samples were analyzed by WD-XRF (Siemens SRS 3000) and ICP-MS (Perkin Elmer, Elan DRC-e) facility at Wadia Institute of Himalayan Geology Dehradun. These granitoids classified as calc-alkaline granite-trondhjemite with metaluminous to peraluminous composition. The negative correlation of ferromagnesian oxide with silica suggests primary magmatic igneous parental melt. Multi-element patterns for the TGC granitoids are characterized by large ion lithophile elements (LILE) enrichment, depletion in high field strength elements (HFSE: Nb, P and Ti) and positive Pb and Zr anomalies. Negative anomalies in HFSE correspond to crustal/lithospheric sources with some influence of K-feldspar, plagioclase and Ti-oxide fractionation. Isotopic data presents the Initial 87Sr/86Sr(t=1.6 Ga) ratio that varies from 0.70595 to 0.73191 for TGC granitoid. Such a range of initial 87Sr/86Sr ratios (> 0.706), corresponding to the TGC granitoid, indicate they are generated within the crust. The elevated value of the initial 87Sr/86Sr ratio may also correspond to the alteration. The geochemical results on the TGC granitoids indicate transitional tectonic settings from “within plate granite” to “volcanic arc syn-collisional granite”.