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

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

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.