Collaborative Research: Helium-isotope Systematics Along Seismic Profiles in Tibet to Study Geometry of Indian and Tibetan Lithosphere

合作研究：沿西藏地震剖面的氦同位素系统学研究印度和西藏岩石圈的几何形状

• 批准号: 1627930
• 负责人: Laura Crossey
• 金额: $ 8.45万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1627930&HistoricalAwards=false
• 关键词: Collaborative; Research; Helium; isotope; Systematics

Himalaya-Tibet is Earth's type example of active continent-continent collision, between India and Asia, yet the plate-scale geometry remains controversial. Researchers from Stanford University and the University of New Mexico will sample and analyze fluids from hot-springs, which are tracers of deeper structure, in the Himalaya and Tibet to locate the northern limit of the Indian lithosphere (and southern limit of the Asian lithosphere), hence the northern limit to which India has been forced (or underthrust) beneath Asia. This effort will improve scientists' ability to draw accurate cross-sections through the Himalaya and Tibet to greater depths than previously possible. This new understanding of Earth?s most dramatic mountain belt and plateau enhances public interest in science, and offers a natural opportunity to integrate earth science into high-school curricula. To this end, a new video about the research project and associated curricular materials designed to meet the Next Generation science Standards will be produced.The lithospheric geometry of continental collision remains controversial. There is no agreement on a single orogenic cross-section in which Indian crust and mantle penetrate a certain distance northwards beneath Tibet. Instead, growing seismological opinion supports models with large changes from west-to-east, from crustal underthrusting to lithospheric delamination (subduction roll-back) to de-blobbing. Stanford has helped acquire and interpret data from multiple seismic transects across Himalaya/Tibet. The interpretations of deep reflectors and converters from these and other published profiles provide testable models for the geometry of Indian and Tibetan lithospheres as it varies from west to east across Tibet. Pilot measurements of 3He/4He ratios in hot springs show significant, and spatially variable, mantle degassing across the Lhasa block in Chinese Tibet (Xizang and Qinghai). The research team will sample geothermal and carbonic fluids and associated travertines at up to 60 new locations in Tibet during two field seasons along several transects chosen for their accessibility, availability of seismic data, and tectonic/geologic setting. The team will analyze 3He/4He, 22Ne, 36Ar, delta13C, delta18O, deltaD, 87Sr/86Sr, major and trace elements to constrain fluid sources (mantle, crustal, atmospheric, sedimentary, organic), to understand fluid mixing and pathways, and to calculate reservoir temperatures using multi-component chemical geothermometry. Seismic data, both broadband teleseismic and near-vertical reflection data, will be re-analyzed to better understand the source regions and transport pathways of the sampled fluids. The data will constrain the boundary between Indian cratonic mantle lithosphere and Tibetan incipiently melting mantle and help define the mantle suture beneath Tibet.

喜马拉雅地带是地球的类型典型的印度和亚洲之间的活跃大陆碰撞的例子，但板规尺度的几何形状仍然存在争议。斯坦福大学和新墨西哥大学的研究人员将在喜马拉雅山和西藏的示踪剂中采样和分析液体，以定位印度岩石圈的北部极限（以及亚洲岩石圈的南部极限），因此印度对印度北部的限制（北部的限制）是对印度北部的限制（或者迫使它被迫使（或不在）。这项努力将提高科学家通过喜马拉雅山脉和西藏的准确横截面的能力，比以前更大。对地球最戏剧性的山带和高原的新了解增强了公众对科学的兴趣，并提供了将地球科学融入高中课程的自然机会。为此，将制定有关旨在满足下一代科学标准的研究项目和相关课程材料的新视频。大陆碰撞的岩石圈几何形状仍然存在争议。在一个单一的造基形横截面上，印度地壳和地幔在西藏以北的一定距离中尚无协议。取而代之的是，越来越多的地震意见支持从西到东部发生巨大变化的模型，从地壳不伪造到岩石圈分层（俯冲滚动倒带）再到开车。斯坦福大学帮助从喜马拉雅/西藏的多个地震横断面获取和解释了数据。这些和其他已发表的概况的深层反射镜和转换器的解释为印度和藏族岩石圈的几何形状提供了可检验的模型，因为它在西藏各地从西部到东方都不同。温泉中3HE/4HE比率的试验测量表现出显着的，并且在空间上可变，地幔在中国西藏（Xizang和Qinghai）的LHASA块中脱气。研究小组将在两个野外季节中在西藏的多达60个新位置进行测量热热和碳流体以及相关的石灰华，沿几个用于可访问性，可访问性的可用性以及构造/地质环境选择的横断面。 The team will analyze 3He/4He, 22Ne, 36Ar, delta13C, delta18O, deltaD, 87Sr/86Sr, major and trace elements to constrain fluid sources (mantle, crustal, atmospheric, sedimentary, organic), to understand fluid mixing and pathways, and to calculate reservoir temperatures using multi-component chemical geothermometry. 地震数据，无论是宽带伸展的和近垂直反射数据，都将被重新分析，以更好地了解采样流体的源区域和运输途径。数据将限制印度cratonic地幔岩石圈和藏族之间的边界，并有助于定义西藏下方的地幔缝合线。