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

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• 作者：C.V. Dharma Rao^a ; ^{Dharma_rao@hotmail.com} ; M. Santosh^b ; Yunpeng Dong^c
• 关键词：U&ndash ; Pb zircon geochronology ; Layered igneous complex ; Subduction ; Mesoproterozoic ; SW Indian plate
• 刊名：Journal of Asian Earth Sciences
• 出版年：2012
• 出版时间：30 April, 2012
• 年：2012
• 卷：49
• 期：Complete
• 页码：362-375
• 全文大小：2991 K

文摘

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 ²⁰⁷Pb/²⁰⁶Pb ages of 1634 ¡À 18 Ma (MSWD = 0.55) for the anorthosite from Pangidi. Two anorthosite samples from Kondapalle yield mean²⁰⁷Pb/²⁰⁶Pb ages of 1628 ¡À 36 Ma (MSWD = 0.54) and 1693 ¡À 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.