中央山系大别、东秦岭和东昆仑造山带最古老岩系变质过程对比

A COMPARISON ABOUT METAMORPHISM AMONG THE OLDEST ROCK UNITS FROM OROGENIC BELTS OF DABIE, EASTERN QINLING AND EASTERN KUNLUN OF THE CENTRAL MOUNTAIN RANGE, CHINA

大别造山带、东秦岭造山带和东昆仑造山带是中国中央山系的主要构成部分，每个造山带古老岩系的变质作用过程各具特色．大别山最古老岩系大别岩群于印支期陆内俯冲碰撞，发生了区域性的中偏高压区域变质作用，顺时针型ｐｔ轨迹上ｔｍａｘ和ｐｍａｘ近于同时达到，退变质轨迹段斜率陡，埋深后受构造驱动快速抬升到上中地壳．东秦岭最古老岩系秦岭岩群在晋宁期（约１．０Ｇａ前）初始板块构造总背景下发生强烈的中压型碰撞变质作用，顺时针型ｐｔ轨迹上ｔｍａｘ在压力大幅度降低的过程中达到，反映弧陆碰撞增厚后深埋岩系受重力均衡抬升；至加里东期，秦岭岩群再次在板块构造的总背景下发生岛弧型变质，局部叠加中压型接触变质作用；晚海西以来北秦岭东段缺乏高于低角闪岩相条件的区域变质作用记录．东昆仑造山带最古老岩系于吕梁或早吕梁期发生中压碰撞区域变质，主体为角闪岩相，局部高角闪岩相－麻粒岩相条件，造山带剥露较浅使低压变质带得以良好保存．

The Dabie Orogen, eastern Qinling Orogen and eastern Kunlun Orogen are the major components of the central mountain range of China and each has distinctively metamorphic processes in their oldest rock units. Intermediate_higher pressure regional metamorphism took place in the oldest rock units of Dabie Orogen during intra_continent collision_subduction event in the Indosinian movement. The clockwise pt path, synchronous attainment of t max and p max and a segment of high slope retrograde path suggest a tectonic_driven rapid exhumation of the oldest rocks to upper_middle crustal level following the end of the subduction. Intensive collision metamorphism occurred in the oldest rock unit of eastern Qinling Orogen at an immature plate tectonic framework during Jinningan Movement about 1000Ma ago. The clockwise pt path with reach of t max following several hundreds of MPa decreasing from p max suggests that denudation of the deeply buried rock unit was due to static gravity relaxation. During the Caledonian stage, the highly metamorphosed oldest rock unit suffered a high_temperature thermal event in arc environment and superimposed by contact metamorphism. After t peaks the rock unit uplifted in a short distance and cooled down isobarically. No regional metamorphism higher than upper greenschist facies since 300Ma has been traced within exposed rocks in the eastern portion of northern Qinling Orogen. In the eastern Kunlun Orogen, the oldest rock unit was regionally metamorphosed to upper amphibolite facies in major and lower granulite facies locally responding to an intermediate_pressure collision event earlier than or during the Lüliang movement. Shallow erosion of the orogenic belt led to the good preservation of the low_pressure metamorphic belt.