Geochemistry and petrogenesis of the sendra granitoid complex southern Delhi fold belt Rajasthan NW India

Abstract

There is long-standing debate regarding origin of A-type granites as compared to most orogenic granites (I-, S- and M-types) due to lack of consensus on their petrogenesis. The current Ph.D. thesis aims at understanding Neoproterozoic crustal evolution of the Aravalli orogen from the perspective of granitoid petrology by elucidating sources, petrogenetic processes and tectonic setting of the Sendra Granitoid Complex. The study area is located in Pali district of Rajasthan and forms a part of the South Delhi Supergroup. The Sendra granitoids occur in the form of five independent plutons, namely Chang, Chitar, Borwar, Seliberi and Jaitpura. The granitoids are foliated and medium grained and are mostly granite in composition, showing some variations towards granodiorite and rare tonalite. All the granitoids show typical features of A-type granites, except the Jaitpura granitoids, which are classified as I-type. The REE patterns of the Sendra granitoids are apparently similar at the scale of individual plutons. The Jaitpura granitoids show significant evidence of fractional crystallization, whereas the others are not much fractionated. The Sendra granitoids show high zircon saturation temperatures (801°- 977°C), and are classified as hot granitoids. It is suggested that the Sendra granitoids were generated predominantly by partial melting of mafic crustal source at high temperatures and emplaced in a post-collisional extensional regime. Moreover, the study provides evidence of the preserved subduction-related post-collisional extensional magmatic rocks during the assembly of the Rodinia supercontinent, which is otherwise relatively less prevalent over intra plate or within plate magmatism during this time period. newline