How Does Mid to Lower Arc Crust Respond to the Transition from Subduction to Collision? Investigation of the Gangdese Orogen Crustal Section

这个项目将研究两个构造板块之间的会聚如何影响大陆地壳的结构、热和成分性质。了解大陆地壳在板块会聚过程中对俯冲和碰撞的反应将有助于深入了解大陆地壳数亿年的演化史，以及构造和岩浆作用如何影响主要山带的地表地形。为了回答这个问题，研究小组将调查藏南冈底斯岩基，它是在印度板块和欧亚板块长期汇聚期间形成的。该项目的主要目标包括建立古冈底斯岩基地壳的横截面，以研究地壳性质(例如，结构和成分)如何沿垂直(深度)剖面变化。为此，研究人员将收集岩石样本以确定它们的压力-温度历史，并研究如何使用保存在这些岩石中的记录来限制地壳厚度、地形高度和质量转移过程的时间变化。该项目的结果将有助于理解构成我们宜居星球基础的大陆地壳的演化，以及地壳的结构和组成如何受到各种类型的固体地球过程的影响。该项目促进了地球科学的多样性，促进了美国和中国科学家之间的国际合作，并支持STEM研究生和本科生以及一名职业生涯早期的研究员。该项目还旨在通过面对面交谈和一个流行的社交媒体平台，增加对K-12学生和更广泛公众的教育宣传。研究成果将通过开放获取的数据库、出版物和在太平洋两岸举行的国际会议传播，包括喜马拉雅研究界。藏南冈底斯造山带中国是地球上仅有的研究大洋-大陆俯冲-陆-陆碰撞转换及其对陆壳构造和演化影响的地点之一。拟议工作的总体目标是建立整个造山带东部的基岩压力和压力-温度-时间-变形(P-T-t-D)历史的区域格架。研究小组将：(1)系统收集冈底斯造山带东部不同构造层次的构造观察和样品，包括较少研究的变质沉积岩暴露；(2)使用各种新的气压计和岩石计时技术建立火成岩和变质沉积岩的P-T-t轨迹；(3)进行结构和电子背散射衍射分析，以量化有限应变形状、强度、变形温度和组构运动学；(4)结合P-T-t-D资料和现有地壳厚度资料，研究冈底斯深部的地质作用过程，以及这些过程在弧岩浆作用向碰撞作用转变过程中和之后的演化。冈底斯造山带为探索变质作用、变形和地壳运动在不同构造阶段的变化提供了独特的机会，所有这些都可以外推到活动的大陆岩浆造山带和其他古老的大陆岩浆造山带，以促进我们对大陆地壳演化的理解。这一奖项反映了NSF的法定使命，通过使用基金会的学术价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will investigate how the convergence between two tectonic plates influences the structural, thermal, and compositional properties of the continental crust. Understanding how continental crust responds to subduction and collision during plate convergence will provide insights into the hundreds-of-million-of-years history of continental crust evolution and how tectonic and magmatic processes influence the surface topography in major mountain belts. In order to answer this question, the research team will investigate the Gangdese Batholith in southern Tibet that was formed during the prolonged convergence between the Indian and Eurasian plates. The major goals of this project include establishing a cross section through the ancient Gangdese Batholith crust to study how crustal properties (e.g., structures and compositions) change along the vertical (depth) profile. To do this, the researchers will collect rock samples to determine their pressure–temperature histories and investigate how the record preserved within these rocks can be used to constrain the temporal variation of crustal thickness, topographic elevation, and mass transfer processes. The results of this project will help in understanding the evolution of the continental crust that forms the foundation of our habitable planet and how the structure and composition of the crust are shaped by various types of solid earth processes. This project promotes diversity in geosciences, fosters international collaboration between US and Chinese scientists, and supports STEM graduate and undergraduate students and one early-career investigator. This project also aims to increase educational outreach with K-12 students and the broader public via in-person talks and through a popular social media platform. Research results will be disseminated through open-access databases, publications, and international meetings held on both sides of the Pacific, including the Himalayan research community. The Gangdese orogen in southern Tibet, China, is one of the only locations on Earth to study the transition from ocean-continent subduction to continent-continent collision and how such transition affects the construction and evolution of the continental crust. The overall goals of the proposed work are to establish the regional framework of bedrock pressures and the pressure–temperature-time–deformation (P–T–t–D) history across the eastern portion of the orogen. The research team will: (1) systematically collect structural observations and samples from different structural levels exposed in the eastern Gangdese orogen, including less-studied metasedimentary rock exposures; (2) use a variety of novel barometers and petrochronometry techniques to establish P-T-t paths of igneous and metasedimentary rocks; (3) conduct structural and electron backscatter diffraction analyses to quantify finite strain shape, intensity, deformation temperatures, and kinematics of fabrics; and (4) integrate P-T-t-D data and existing crustal thickness data to investigate geological processes operating in the deep Gangdese crust and to investigate how these processes evolve during and after the transition from arc magmatism to collision. The Gangdese orogen provides a unique opportunity to probe how metamorphism, deformation, and crustal flow vary during different tectonic stages, all of which can be extrapolated to active and other ancient continental magmatic orogens to advance our understanding of the evolution of the continental crust. held on both sides of the Pacific, including the Himalayan research community.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.