柴北缘鱼卡硬柱石榴辉岩的岩石学、地球化学和年代学研究

本申请拟以在柴北缘鱼卡河地区新发现的硬柱石假象榴辉岩为重点研究对象，在详细野外地质调研的基础上，对鱼卡河剖面不同类型的榴辉岩及围岩片麻岩进行系统的矿物学、岩石学、地球化学和年代学的综合研究，查明鱼卡地体中硬柱石榴辉岩与其他不同类型榴辉岩的空间分布和相互关系；通过矿物结构和成分研究并结合相平衡计算，确定榴辉岩及其围岩片麻岩的PT演化过程，并确定它们是否经历过超高压变质作用；查明含硬柱石榴辉岩的原岩属性和时代；综合利用锆石、独居石、榍石等副矿物U-Pb体系定年方法，确定榴辉岩和片麻岩的形成、变质或可能的退变质时代。在与已有超高压多硅白云母榴辉岩进行详细对比的基础上，重建鱼卡超高压变质地体的形成和演化历史，进而为整个柴北缘超高压带从洋壳俯冲到陆壳碰撞模式，以及柴北缘造山带的热结构探讨提供重要制约

Based on detailed field investigation, this project will mainly focus on the petrological, geochemical and geochronological studies on different kinds of eclogite, especially the new discovered lawsonite bearing eclogite, and their country rock gneisses in Yuka terrane, the North Qaidam UHP metamorphic belt. First of all figure out the distributions of these different eclogites and the relationship between the lawsonite eclogite with others. By means of texture observation and composition analyses on minerals from different generations combining with phase equilibria modelling, we try to establish P-T evolution path for these eclogites and gneisses, and confirm whether they underwent UHP metamorphism; ascertain the protoligh affinity and age of lawsonite eclogites. Using multiple dating methods of U-Pb dating for zircon, rutile and tatanite, we will try to constrain the formation age, metamorphic age and possible retrograde age for eclogites and geiness. Furthermore, through detailed comparison between lawsonite eclogite and the well constrained UHP phengite eclogite, this project will reconstruct the formation and evolution history of Yuka UHP terrane and finally provide vital constraints on the tectonic model of from oceanic subduction to continental collision and the orogen thermal structure of the North Qaidam UHPM belt.