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

00033555刘这个项目的重点是中国中东部苏鲁超高压（UHP）变质地块一个5公里钻孔附近的区域。该项目的目标是通过研究来自P-T条件“禁区”（即非常高的P，非常低的T）的超镁质（地幔）岩石来了解UHP岩石的形成和发掘。需要解决的一些具体问题是：当大陆俯冲时，发生了何种类型的壳幔相互作用？o有多少大陆块以这种方式被循环利用？流体-岩石相互作用的时间能否受到限制？o UHP石榴石橄榄岩告诉我们关于“岩石构造”过程的什么信息？超高压橄榄岩是如何嵌入地壳的？在挖掘过程中它们是如何进化的？需要什么样的上升机制和上升速率来保持它们的高P低T组合？板块含水相在将挥发物再循环到地幔中起什么作用？o我们能否利用深地震剖面来区分较年轻造山带的俯冲/碰撞构造？在什么样的构造背景下，超高压变质作用和随后的发掘发生？大陆与大陆之间是否需要碰撞？首席研究员将在他们的研究中采用多种方法：1)制图和结构分析；2)岩石与地球化学；3)地质年代学;4)东海钻井现场地球物理；5)地球动力学建模

0003355LiouThis 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.***