西秦岭地区秦岭岩群的变质作用研究—对中央造山系秦-祁-柴-昆高压-超高压变质岩带之间关系的约束

西秦岭地处中央造山系中段，既是中央造山系东西转换的关键，又是连接秦岭造山带、祁连造山带和昆仑造山带的纽带。本项目拟以前期研究在西秦岭秦岭杂岩中发现的高级变质作用线索为切入点和突破口，在详细的岩相学、矿物学、包体矿物学以及矿物出溶体成分、形态和结构研究的基础上，结合变质相平衡计算、岩石地球化学和年代学研究，寻找和确定高压-超高压变质的证据，确定它们变质作用的P、T条件和P-T轨迹，确定峰期变质和退变质的时代。在此基础上，通过与东秦岭、北祁连、柴北缘以及东昆仑高级变质岩石在变质岩石组合、峰期变质时代和变质作用P-T轨迹的详细对比，探讨东秦岭古生代的高压-超高压变质岩带：①是否可延伸到西秦岭？②从西秦岭再往西是与北祁连还是柴北缘或者东昆仑相连？最终为进一步探讨早古生代时期中央造山系中西部的构造格局和演化过程提供重要约束。

The West Qinling orogen is situated at the middle of the central orogenic system of China. It connects the East Qinling orogenic belt to the east and Qilian and Kunlun orogenic belts to the west. Taking the new clues for the high grade metamorphism in Qinling Complex from the West Qinling as breakthrough point, this project will carry out detailed petrography, mineralogy, mineral inclusion and exsolution texture study to find high pressure-ultrahigh pressure evidences in West Qinling. And based on phase equilibrium modelling technique, geochemistry and geochronology study, we devote to the confirmation of the P-T path and peak and retrograde metamorphic ages of the high grade metamorphic rocks in West Qinling. Eventually, by comparing the rock assemblages, peak metamorphic ages and P-T paths of the high metamorphic rocks in West Qinling, East Qinling, North Qilian, North Qaidam and East Kunlun, we will discuss the problems of ① whether the Early Paleozoic East Qinling high pressure-ultrahigh pressure metamorphic belt could extend to West Qinling; and ② the relationship between the West Qinling and North Qilian, North Qaidam and East Kunlun ultrahigh pressure metamorphic belts in the west. All of these results will provide important constraints for the tectonic framework and evolution history of the midwest part of the central orogenic system in Early Paleozoic.