U-Pb zircon chronology of the Pangidi-Kondapalle layered intrusion, Eastern Ghats belt, India: Constraints on Mesoproterozoic arc magmatism in a convergent margin setting

The Pangidi-Kondapalle layered intrusion is emplaced within high-grade supracrustal rocks in the southern sector of the Eastern Ghats Granulite Belt proximal to the south-eastern periphery of the Indian plate. This layered complex consists mainly of anorthosites and gabbronorites with pyroxenite cumulates containing orthopyroxenites and chromitites in a regressive intrusive sequence. Here we report laser ablation ICP-MS data and REE geochemistry of zircons from three co-spatial anorthositic bodies in this complex. Our results show mean Pb-207/Pb-206 ages of 1634 +/- 18 Ma (MSWD = 0.55) for the anorthosite from Pangidi. Two anorthosite samples from Kondapalle yield mean(207)Pb/Pb-206 ages of 1628 +/- 36 Ma (MSWD = 0.54) and 1693 +/- 110 Ma (MSWD = 5.5). The zircons from all the anorthosite samples show high REE contents, prominent HREE enrichment and a conspicuous positive Eu anomaly, suggesting a common melt source. The prominent Mesoproterozoic ages revealed from our U-Pb dating of zircons from these layered complexes suggest subduction-related magmatic underplating in a convergent margin setting associated with the amalgamation of the Columbia-derived fragments within the Neoproterozoic supercontinent. (c) 2011 Elsevier Ltd. All rights reserved.