Petrology and Mineral Chemistry of Picrite Sill from Peddakudala-Velpula Area, in Southwestern Part of the Proterozoic Cuddapah Basin, Andhra Pradesh, India - Chapter 7 - 2011-

Uranium (Nuclear Minerals) / Exploration, Mining, Marketing, & Acquisitions

V.V. Sesha Sai reported in 2011 that Mafic-ultramafic magmatism constitutes an integral part of evolution of Dharwa craton, having taken place repeatedly at various stages of its development Basaltic sills and lava flows (∼1.88 Ga) are commonly intercalated with sediments in the lower part of the sedimentary sequence in the intra-cratonic, mid-Proterozoic Cuddapah basin of southern India. The Proterozoic Cuddapah basin of Peninsular India covering an area of around 44,000 km² in the state of Andhra Pradesh, is one of the well known Proterozoic sedimentary basins in the world. Contemporaneous with the sedimentation, Cuddapah basin has witnessed number of phases of igneous activity during the course of its evolution

Six phases of igneous activity are recorded in Cuddapah basin. Sub-aerial eruption of basic lava flows after the deposition of Vempalli Formation marks the first phase of igneous activity within the basin. The volcanic activity represented by fine grained basic rocks and tuffs within the Tadpatri Formation represents the second phase of igneous activity and intrusion of sills of picritic and doleritic composition into the Vempalle and Tadpatri succession marks the third phase of igneous activity. The barium and iron oxide rich volcanic activity which was contemporaneous with the Pullampet/Cumbum Formation represents the fourth phase, while intrusion of basic dykes and alkaline rocks (riebeckite syenites of Giddaluru-Racherla-Idamakallu-Dhupadu and Chelima Lamproite) into the rocks of Nallamalai Fold Belt represents the fifth phase of igneous activity. The sixth phase of igneous activity is represented by intrusion of granitic rocks into the Nallamallai Group in the northeastern fringes of the Cuddapah basin. However, later work revealed that the Nakerikallu and Ipuru granitoids are traversed by dolerite dykes.

A number of NNW-SSE to NW-SE trending sills of picrite, dolerite and olivine gabbro compositions are emplaced parallel to the south western margin of Cuddapah basin. The present paper pertains to petrology and mineral chemistry of a major NW-SE trending picrite body in southwestern part of Cuddapah basin.