The Deformation History of the India-Asia Suture Zone, Lopukangri Rift, South-Central Tibet

西藏中南部洛布岗日裂谷印亚缝合带的变形历史

• 批准号: 0711527
• 负责人: Michael Murphy
• 金额: $ 29.98万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711527&HistoricalAwards=false
• 关键词: Deformation; History; India; Asia; Suture

Quantitative tectonic models that explain the evolution of deep-crustal rocks in the Tibet-Himalayan orogen call upon processes which link them to the suture zone between India and Asia. Inherent in all models that describe the dynamics of the suture zone are predictions of the kinematic history, origin, and pressure-temperature-time evolution of suture zone rocks. This project, carried out by a research team from the University of Houston in collaboration with scientists from the Chinese Academy of Sciences, exploits a rare exposure of the deep and shallow portions of the suture between India and Asia, the Indus-Yalu suture zone, in south-central Tibet afforded by the Lopukangri rift, a rift that extends approximately 150 km from the Lhasa terrane into the Indian subcontinent. Reconnaissance studies of the rift show that its uplifted footwall provides a window into the deformation history of deep suture zone rocks, while the history of the shallow portion of the suture zone is archived in its hanging wall. The goals are to determine: 1) the crustal architecture and kinematics of deformation within the India-Asia suture zone; 2) the derviation of the suture zone rocks (subducted Indian plate or Asia); 3) determine the nature and timing of metamorphism in the suture; 4) the exhumation rate of the metamorphic suture zone rocks; 5) the relationship between the geologic history recorded in deep suture zone rocks to that of the shallow crustal regions and the Himalayan thrust belt. The deformation history, petrogenesis, and thermal history of suture zone rocks will be examined using a variety of techniques including field mapping and structural analysis, thermobarometry, Nd isotope geochemistry, 40Ar/39Ar thermochronology, and Sm-Nd garnet geochronology. The resulting data will directly address the predictions of models for Tibet-Himalayan orogenesis and suture zone dynamics.The Tibet-Himalayan orogen is a paradigm for active continental collision; hence studies of its evolution have played a major role in shaping the conceptual understanding of mountain-building processes and continental growth by accretion. While numerous geodynamic models of mountain building have emerged from geologic and geophysical studies of the Tibet-Himalayan Range, their predictions for the behavior of middle and lower crust remain largely untested because access to deep rocks is, in general, limited to the frontal regions in the High Himalaya. This project exploits an unusual exposure of these deep rocks in the interior of the range and employs techniques in isotope geochemistry, geochronology, and geological mapping of the to address processes hypothesized to operate during intercontinental collision, such as, the deep structure of suture zones, and the rates at which suture zone rocks are translated from great depths to the surface. Integration and analysis of these new observations with existing geologic and geophysical data from other parts of the Himalaya and Tibet will significantly impact the conceptual understanding of the evolution of mountains belts and continents. The project involves a significant collaboration with Chinese scientists, supports early career researchers, and actively promotes participation of underrepresented groups in earth science research.

解释西藏-喜马拉雅造山带深地壳岩石演化的定量构造模型，要求将它们与印度和亚洲之间的缝合带联系起来。固有的所有模型，描述缝合带的动力学是预测的运动历史，起源，和压力，温度，时间演化的缝合带岩石。该项目由休斯顿大学的一个研究小组与中国科学院的科学家合作开展，利用了印度和亚洲之间的缝合线的深部和浅部的罕见暴露，即印度-雅鲁藏布江裂谷提供的印度-雅鲁藏布江缝合带，该裂谷从拉萨到印度次大陆延伸约150公里。对裂谷的勘测研究表明，它隆起的下盘为了解深部缝合带岩石的变形历史提供了一个窗口，而缝合带浅部的历史则保存在其上盘。目标是确定：1）印度-亚洲缝合带的地壳结构和变形运动学; 2）缝合带岩石的变形（俯冲的印度板块或亚洲）; 3）确定缝合带变质作用的性质和时间; 4）变质缝合带岩石的折返速率;（5）深缝合带岩石记录的地质历史与地壳浅部和喜马拉雅冲断带的地质历史的关系。变形历史，岩石成因，缝合带岩石的热历史将使用各种技术，包括现场测绘和结构分析，热压，Nd同位素地球化学，40 Ar/39 Ar热年代学，Sm-Nd石榴石地质年代学检查。由此产生的数据将直接解决西藏-喜马拉雅造山带和缝合带动力学模型的预测。西藏-喜马拉雅造山带是一个活跃的大陆碰撞的范例;因此，其演化的研究在塑造造山过程和大陆增长的概念理解中发挥了重要作用。虽然从西藏-喜马拉雅山脉的地质和地球物理研究中已经出现了许多造山运动的地球动力学模型，但它们对中地壳和下地壳行为的预测在很大程度上仍然未经检验，因为进入深部岩石的途径通常仅限于高喜马拉雅山脉的前沿地区。该项目利用了这些深层岩石在山脉内部的不寻常暴露，并采用了同位素地球化学，地质年代学和地质测绘技术，以解决假设在洲际碰撞期间运作的过程，例如缝合带的深层结构，以及缝合带岩石从很深处转移到表面的速率。将这些新的观测结果与喜马拉雅山和西藏其他地区现有的地质和地球物理数据相结合并进行分析，将大大影响对山脉带和大陆演化的概念性理解。该项目涉及与中国科学家的重要合作，支持早期职业研究人员，并积极促进代表性不足的群体参与地球科学研究。