Geochemistry and strontium isotopic composition of basalts from the Eastern Deccan volcanic province, India

Abstract

Summary Ten rather uniform tholeiitic basalt flows totalling a thickness of 190 m from Sagar, India, contain two stratigraphical breaks. Major element variation allows the flows to be grouped into two eruption cycles. Due to intraflow variation, however, chemical composition is unlikely to be useful in widespread correlation of flow sequence. The initial 87 Sr/ 86 Sr ratios vary from 0·7039 to 0·7084 with Rb and Sr averaging 6·5 and 184 ppm respectively and Rb/Sr ratios ranging from 0·002 to 0·224, with no systematic relationship between the initial 87 Sr/ 86 Sr ratios and other chemical parameters. Bulk crustal contamination is considered unlikely; selective introduction of 87 Sr from the granitic basement is postulated.