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

西藏雅鲁藏布江缝合带玄武岩同位素研究白垩纪东塞提斯地幔源区

• 批准号: 9805318
• 负责人: John Mahoney
• 金额: $ 14.05万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-01 至 2001-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9805318&HistoricalAwards=false
• 关键词: Investigation; Cretaceous; East; Thethyan; Mantle

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.

9805318 mahoney印度洋脊玄武岩的地幔源具有与太平洋和北大西洋脊不同的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，或者它可能是中生代冈瓦纳北部现已消失的特提斯洋的地幔继承的一个更古老的特征。然而，特提斯地幔的性质尚不为人所知，因为目前很少有同位素或微量元素的数据显示来自该地幔源的物质。为了解决我们知识上的这一空白，进而解决印度洋地幔独特同位素特征的更大问题，将对特提斯海洋地壳进行系统的调查，其碎片保存在南亚南特提斯缝合带的陆地上。美国研究人员将对收集的玄武岩和辉长岩样品进行年龄校正后的Nd、Pb和Sr同位素比率以及各种微量元素的分析。这些数据将与中国团队的岩石学、构造学和地质年代学研究一起获得。该项目将为地幔演化和动力学的基本问题提供新的见解，同时促进中美研究人员和学生之间的合作和科学交流。