甘肃敦煌观音沟地区变质作用初步研究  

Preliminary report on the metamorphic evolution of the Guanyingou amphibolites,Dunhuang Metamorphic Complex,NW China

作　　者：彭涛[1] 王浩[1] 陈泓旭[1] 孟洁[1] 卢俊生[1] 王国栋[1] 吴春明[1] 

机构地区：[1]中国科学院大学地球科学学院,北京100049

出　　处：《岩石学报》2014年第2期503-511,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41372199;41225007)资助

摘　　要：敦煌东南三危山观音沟地区,出露有石榴斜长角闪片麻岩,岩石中保存了三个阶段的变质矿物组合。进变质阶段的矿物组合（M1）以石榴子石变斑晶中的包裹体矿物组合（Hbl1＋Pl1＋Qtz1）为代表,形成条件约为550-575℃/5.2-5.7kbar（绿帘角闪岩相）。变质高峰期矿物组合（M2）主要由石榴子石变斑晶和基质矿物（Hbl2＋Pl2＋Qtz2±Cpx2）组成,形成温度〉670℃,压力〉11.9kbar（角闪岩相）。退变质阶段矿物组合（M3）为后成合晶矿物组合（Hbl3＋Pl3＋Qtz3）,形成条件约为590-640℃/4.3-5.9kbar（角闪岩相）。观音沟石榴斜长角闪片麻岩记录了包含进变质、变质高峰、退变质过程的造山过程＂西阿尔卑斯＂型P-T轨迹,其中退变质阶段具有明显的近等温降压特征。变质作用P-T轨迹指示本地区可能经历了俯冲-碰撞-快速抬升的造山过程。结合年代学资料,该期造山事件可能发生于泥盆纪。Exposed in the Guanyingou area,Mt. Sanweishan,Dunhuang,NW China,the garnet-bearing amphibolites record different metamorphic mineral assemblages formed during three metamorphic stages. The prograde assemblage（ M 1）,enclosed in garnet porphyroblast,is consisted of hornblende,plagioclase and quartz and the P-T conditions were estimated to be 550~575℃ /5. 2~5. 7kbar（ epidote amphibolite facies）. The metamorphic peak assemblage（ M 2） is composed mainly of garnet and hornblende, plagioclase,quartz and locally clinopyroxene in the matrix,with P-T conditions estimated to be of 670℃ and 11. 9kbar（ amphibolite facies）. The retrograde assemblage（ M 3） is the so-called＂white-eye socket＂symplectite rimming garnet porphyroblast, consisted mainly of hornblende,plagioclase and quartz,and were formed at about 590~640℃ /4. 3~5. 9kbar（ amphibolite facies）. Micropetrographic investigation and thermobarometric computation show that the amphibolites experienced clockwise,west-Alpine type P-T paths including near isothermal decomposition（ ITD） segments,suggesting that the terrane involved in a collisional orogenic process,possibly in the Devonian.

关 键 词：斜长角闪片麻岩 矿物温度计 矿物压力计 变质作用P-T轨迹 敦煌变质杂岩 

分 类 号：P588.345[天文地球—岩石学]