西藏班戈节浪垭地区念青唐古拉群变质作用特征  

Metamorphic characteristics of Nyainqentanglha Group in Jielangya area of Bange,Tibet

作　　者：朱志勇[1] 王天武[1] 李才[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061

出　　处：《世界地质》2004年第2期128-133,共6页World Geology

基　　金：中国地质调查局区域地质调查项目资助(H45C002004)

摘　　要：西藏念青唐古拉山的西端出露一套中、低级变质岩,主要有:斜长角闪岩、云母片岩、斜长片麻岩和大理岩等。研究表明,该变质岩经历了两期变形作用的改造,第一期变形稍滞后于变晶作用,形成岩石片理;第二期变形是在片理之上叠加了折劈理。经电子探针分析,岩石中的角闪石、透辉石、石榴石、黑云母和斜长石等单矿物均为变质成因的矿物。利用矿物对该变质岩的变质作用温、压条件进行了计算,分别为:T=540～695 ℃,P=0.4～0.67 Gpa。研究区角闪石Ar-Ar同位素年龄测定,其年龄为(845±1)Ma,表明其变质时代为新元古代。A suit of mid-low grade metamorphic rocks are exposed in western margin of the Nyainqentanglha mountain. The rocks mainly consist of plagioclase-amphibolites,mica-schist,plagioclase gneisses,marbles,etc. The metamorphic rocks have undergone metamorphism in two stages,including the first stage of metamorphism forming schist being slightly later than the crystalloblastesis;and the second stage of metamorphism forming crenulation cleavage after the schist. The analysis with electron microprobe proved that the amphibole,diopside,garnet,biotite and plagioclase in the rocks are metamorphic minerals. Using mineral groups,the authors calculated the metamorphic temperature and pressure conditions of the rocks as 540 to 695℃ and 0.4 to 0.67 Gpa. The Ar-Ar isotopic dating result are(845±1)Ma indicating that these metamorphic rocks were formed in Neoproterozoic metamorphic process.

关 键 词：西藏班戈 念青唐古拉群 变质作用 温压条件 新远古代 

分 类 号：P511.5[天文地球—地质学]