The Ahar River Granite, Its Stratigraphic and Structural Relations with the Early Proterozoic Rocks of South-Eastern Rajasthan

Abstract

The Ahar River granite near Udaipur city, considered by Heron as intrusive into the Aravalli rocks of early Proterozoic age, is a coarse-grained, massive, leucocratic rock except along the outcrop margins. The granite ranges in composition from alkali granite to granodiorite and tonalite, with about 5% ferromagnesian minerals. The enveloping Aravalli metasediments form a continuous sequence starting with greenschist (metavolcanics) and quartzite (locally conglomerate) along the granite contact. The stratigraphic position of the Ahar River granite in relation to the surrounding metasediments suggests that the granite is the basement rock. The granite characteristically shows post-crystalline deformation of the constituent grains, specially quartz and feldspar; and the granite-cover contacts are marked by ductile shear zones developed during the earliest deformation of the Aravalli rocks.