Collaborative Research: Subduction and Exhumation of Ulltrahigh-Pressure Rocks -- Field and Drilling Studies in Eastern China

Stanford University, Stanford CA

Investigators

Abstract

0003355 Liou This project is focused on the area around a 5 km drill hole the Chinese are going to drill in the Sulu ultrahigh-pressure (UHP) metamorphic terrane in east-central China. The goal of the project is to understand the formation and exhumation of UHP rocks through study of ultramafic (mantle) rocks from a "forbidden zone" of P-T conditions (i.e., very high P, very low T). Some specific questions to be addressed are: o What type of crust-mantle interaction occurs when continents are subducted? o How much of continental mass is recycled in this manner? o Can timing of fluid-rock interactions be constrained? o What do the UHP garnet peridotites tell us about "petrotectonic" processes? o How were UHP peridotites emplaced into the crust? How did they evolve during exhumation? What mechanisms and rates of ascent are necessary to preserve their high P, low T assemblages? o What roles do slab hydrous phases play in recycling of volatiles into the mantle? o Can we tell the difference between subduction/collisional architecture of orogens from younger events using deep-seismic profiles? o In what tectonic settings does UHP metamorphism and subsequent exhumation occur? Is continent-continent collision required? The Principal Investigators will employ a variety of methods in their study: 1) mapping and structural analysis; 2) petrology & geochemistry; 3) geochronology; 4) geophysics at the Donghai drill site; and 5) geodynamic modeling. ***