【摘要】 北天山西部温泉岩群中新发现的石榴角闪岩对于研究中亚造山带的形成与演化具有重要意义。详细的岩相学和相平衡模拟的结果表明,石榴角闪岩的变质演化过程可以划分为三个阶段:(1)升温升压进变质阶段,以石榴子石中包裹绿帘石为特征,矿物组合为石榴子石+角闪石+斜长石+石英+钛铁矿+绿帘石,峰期变质条件为700℃/9. 6kbar,可能发生的变质反应为角闪石+绿帘石+石英→石榴子石+斜长石+水;(2)近等温降压退变质阶段,以石榴子石周围发育由"斜长石+石英+角闪石"组成的"白眼圈"结构为特征,可能发生的变质反应为石榴子石+石英+水→角闪石+斜长石;(3)降温降压退变质阶段,以石榴子石发育绿泥石化为特征。结合前人研究成果,推测石榴角闪岩形成于晚奥陶世古亚洲洋俯冲消减的环境中。更多还原

【Abstract】 The newly discovered garnet amphibolites in the Wenquan Group,western North Tianshan,China,are of great significance for providing valuable insights into the formation and evolution of the Central Asian Orogenic Belt. The detailed petrography and phase equilibria modeling reveal that the metamorphic evolution of the garnet amphibolite can be divided into three stages:（ 1） the prograde metamorphic stage with heating and pressure increase,characterized by epidote wrapped by garnet,a mineral assemblage of garnet + hornblende + plagioclase + quartz + ilmenite + epidote and a peak P-T of 700℃/9. 6 kbar,which is suggested to be dominated by a continuous dehydration reaction: hornblende + epidote + quartz → garnet + plagioclase + H₂O;（ 2） the metamorphic stage with isothermal decompression,featured with " white-eye socket" textures made up of " plagioclase + hornblende + quartz",which may be controlled by the reaction garnet + quartz + H₂O→hornblende + plagioclase;（ 3） the retrograde stage with cooling and decompression,featured with chlorite developing along the fractures of garnet. Combined with previous results,it is speculated that the garnet amphibolite was formed during subduction and erosion of the Paleo-Asian Ocean in the Late Ordovician.更多还原