Investigation of Cretaceous East Thethyan Mantle Sources Through An Isotopic Study of Yarlung-Zangpo Suture Zone Basalts, Tibet

9805318 Mahoney印度洋海岭玄武岩的地幔源区具有不同于太平洋和北大西洋海岭玄武岩的Pb-Nd-Sr同位素特征。印度洋地幔特征的原因尚不清楚：它可能起源于冈瓦纳超大陆的分裂，或者它可能是从中生代冈瓦纳北部现已消失的特提斯洋地幔继承的一个更古老的特征。然而，特提斯地幔的性质知之甚少，因为很少有同位素或微量元素数据存在有限的现代暴露的物质来自这个地幔源。为了弥补我们知识中的这一空白，进而解决印度洋地幔独特同位素特征这一更大的问题，将对保存在南亚南特提斯缝合带陆地上的特提斯洋地壳碎片进行系统调查。在一个难得的机会中，美国调查人员被邀请参加中国的一个考察队，在藏南雅鲁藏布江缝合带（Yarlung-Zangpo suture zone）研究特提斯海底碎片，该缝合带是南特提斯缝合带最长的一段。美国研究人员将对采集的玄武岩和辉长岩样品进行Nd、Pb和Sr同位素比值校正和多种微量元素分析。这些数据将与中国团队的岩石学、构造和年代学研究相结合。该项目将为地幔演化和动力学的基本问题提供新的见解，同时也促进了中美研究人员和学生之间的合作和科学交流。

9805318MahoneyThe mantle sources of Indian Ocean ridge basalts have a Pb-Nd-Sr isotopic signature distinct from those of the Pacific and North Atlantic ridges. The reason for the Indian Ocean mantle signature is unknown: it may have originated with the breakup of the supercontinent of Gondwana, or it may be an older feature inherited from the mantle of the now-vanished Tethyan Ocean which lay to the north of Gondwana in the Mesozoic. However, the nature of Tethyan mantle is poorly known as few isotopic or trace element data exist for the limited present-day exposures of materials derived from this mantle source. To address this gap in our knowledge, and in turn the larger issues of the unique isotopic signature of the Indian Ocean mantle, a systematic investigation of Tethyan Ocean crust, fragments of which are preserved on land in the South Tethyan suture belt of southern Asia, will be conducted. In a rare opportunity, the American investigators have been invited to join a Chinese expedition working on Tethyan seafloor fragments exposed in the Yarlung-Zangpo suture zone of southern Tibet, one of the longest stretches of the South Tethyan suture belt. Age-corrected Nd, Pb, and Sr isotopic ratios and a variety of trace elements will be analyzed by the US researchers on basalt and gabbro samples collected. These data will be obtained in conjunction with petrological, structural, and geochronological studies by the Chinese team. This project will provide new insights on fundamental questions of mantle evolution and dynamics while also promoting cooperation and scientific exchange between US and Chinese researchers and students.