【摘要】 高级变质富铝片麻岩出露于辽东岫岩北部王家堡子一带南辽河岩群变质岩石中,通过详细的岩相学和变质作用研究,确定其变质峰期典型矿物组合为Sil+Grt+Crd+Bt+Pl+Kfs+Qz;峰期后存在典型的减压反应Grt+Sil+Qz→Crd。早期进变质阶段以出现十字石、蓝晶石为特征,晚期退变质阶段以石榴石变斑晶和黑云母转变为绿泥石为特征。传统地质温压计估算的富铝片麻岩峰期变质条件为:T=640℃～690℃,P=5. 5～7. 0 kbar;峰期后减压阶段变质条件为:T=560℃～660℃,P=4. 7～4. 9kbar;晚期退变质条件为:T=520℃～560℃,P=2. 9～3. 0 kbar。矿物组合特征、矿物相转变结构及其温压条件变化反映其具有近等温减压的顺时针P--T轨迹演化特征,不同于前人所获得的逆时针P--T轨迹。研究结果认为南、北辽河岩群在古元古代可能经历了相同的变质作用演化过程。更多还原

【Abstract】 The study on petrography and metamorphism of aluminum-rich gneiss occurred in South Liaohe Group in Wangjiapuzi of northern Xiuyan area,East Liaoning has been carried out. The peak mineral assemblage consists of garnet + sillimanite + cordierite + biotite + plagioclase + k-feldspar + quartz,and there is a typical decompression reaction of garnet + sillimanite + quartz→cordierite after peak stage. Early prograde metamorphic stage is characterized by the occurrence of staurolite and kyanite,whereas the late retrograde metamorphic stage is characterized by the transformation of garnet and biotite into chlorite. Traditional P--T estimation suggests that the metamorphic conditions for peak stage are 640℃ ～ 690℃ and 5. 5 ～ 7. 0 kbar of aluminum-rich gneiss,560℃ ～ 660℃and 4. 7 ～ 4. 9 kbar for post-peak near-isothermal decompression stage,and 520℃ ～ 560℃ and 2. 9 ～ 3. 0 kbar for late retrograde metamorphic stage. The characteristics of mineral assemblage,transition structure of mineral phase and P--T conditions of aluminum-rich gneiss indicate a clockwise P-T path with near isothermal decompression,which is different from the counterclockwise P--T path obtained by predecessors. The results show that South Liaohe Group and North Liaohe Group probably underwent the same metamorphic evolution process in Paleoproterozoic.更多还原