Isotopic Studies of Deccan and Parh Group Basalts, and East Tethyan and Old Western Indian Ocean Seafloor

该项目将(1)继续成功开展与印度德干圈闭相关的地球化学工作，(2)研究浩瀚而神秘的印度洋地幔域的起源。最近的模型将德干事件归因于快速移动的大印度之下的留尼汪羽头的撞击；然而，Basu等人1993年对德干火山北部的碱性侵入物进行的研究表明，留尼汪热点在德干火山主要喷发前至少3万年就存在了。建议对收集的Parh玄武岩进行Nd、Pb、Sr同位素和ICP-MS微量元素分析，以确定它们是否确实是留尼旺早期热点产物。最近的研究表明，现代印度洋MORB具有与太平洋和北大西洋MORB截然不同的Pb-Nd-Sr同位素特征。然而，这个巨大的地幔域的早期历史是不确定的，它是随着冈瓦纳大陆的分裂和印度洋的开放而起源和发展，还是从东特提斯洋软流圈继承而来的一个更古老的特征，也不得而知。建议分析Pb、Nd和Sr同位素微量元素，必要时分析来自西印度洋DSDP遗址的主要元素，以及保存在马西拉、雅鲁藏布江和俾路支省蛇绿岩中的东特提斯海底岩浆单元，以回答这个问题。

9418168 Mahoney This project will (1) continue successful geochemical work related to the Deccan Traps of India, and (2) investigate the origins of the vast but enigmatic Indian Ocean mantle domain. Recent models attribute the Deccan event to impact of the Reunion plume head beneath a fast-moving Greater India; however, a study of alkalic intrusions north of the Deccan by Basu et al. 1993 suggests that the Reunion hotspot existed at least 3 m.y. before the main Deccan eruptions. Propose to analyze a collection of Parh basalts for Nd, Pb, and Sr isotopes and ICP-MS trace elements, in order to establish whether they are indeed early Reunion hotspot products. Recent investigations have shown that modern Indian Ocean MORB, has a Pb-Nd-Sr isotopic signature quite distinct from that of Pacific and North Atlantic MORB. The earlier history of this immense mantle domain is uncertain, however, and whether it originated and grew with the breakup of Gondwana and the opening of the Indian Ocean, or is an older feature inherited from the East Tethyan Ocean asthenosphere is unknown. Propose to analyze Pb, Nd, and Sr isotopes trace elements and , where necessary, major elements from DSDP sites in the western Indian Ocean, and magmatic units of East Tethyan seafloor preserved in the Masirah, Yarlung-Zangpo, and Baluchistan ophiolites in order to answer this question.