豫西蛇尾秦岭群P-T轨迹定量计算及其地质意义

THE P-T PATHS OF QINLING GROUP AND THEIR IMPLICA-TIONS FOR THE EVOLUTION OF METAMORPHIC ENVI-RONMENT, TECTONISM AND MIGMATISM

河南省西峡县北部蛇尾地区秦岭群变质泥质岩系的黑云二长榴线岩中的石榴石成分环带是连续变质反应的结果。本文根据该岩石的石榴石环带成分定量计算了变质作用P-T轨迹。P-T轨迹样式表明,本区秦岭群的变质作用可以分为两大期:第一期发生在大陆碰撞带环境中,变质的温度压力演化受均匀地壳增厚及隆起侵蚀过程控制;第二期发生在岛弧环境或活动大陆边缘环境,变质温压条件早阶段与深部上升的热流有关,中阶段受侵位的炽热花岗岩体控制,晚阶段受地体背冲推覆的构造过程制约。

The zoned garnets of tne metapelites from Qinling Group in Shewei area, Xi-Jtia county, Henan Province can all be attributed to the continuous reactions. According to the garnet zoning, the patterns of the P-T paths by quantitative calculation show that there have been two important metamorphic events occurring in the past. The first metamorphic event took place in the tectonic environment of continental collision zone. The geological factors that controlled the pressure and temperature conditions were the processes of uniform crustal thickening and uplift. The second event occurred in the arc tectonic setting. At the earlier stage, the P/T condition was controlled by the heat flow raising from the deep crust. At the middle stage, it was controlled by the intrusion of hot granitic body, and by the processes of the opposite thrust of Qinling Group onto the Lower Palaeozoic fold belts at the later stage.