Geochemical Constraints on Anorogenic Felsic Plutonism in North Delhi Fold Belt, Western India

Ajitgarh pluton, along the northwestern fringe of Indian peninsular shield, is a composite trondhjemite-alkali granite body. Both the granitoid types, intrusive into metasediments of Delhi Supergroup, represent different pulses of anorogenic magmatism. The granitoids, post-dating the major deformational phase, demonstrate a time relationship with each other. Subtle variations in mineralogy and geochemistry indicate distinctive petrogenetic lineage for both the granitoids. Their tectonic setting, mineralogical compositions and geochemical signatures are consistent with A-type granites and an igneous source. rh granitoids are quite distinct from other syn-orogenic, S-type granite massifs (1700-1500 Ma) of North Delhi Fold Belt and appear to be related to the late Proterozoic anorogenic magmatism associated with rejuvenation of the rift system that controlled the Delhi sedimentation. All the granitoid bodies within North Delhi Fold Belt have so far been presumed to be syn-orogenic and coeval at 1700-1500 Ma.