帕米尔高原沙克达拉穹窿变质作用及新生代下地壳演化  

The Cenozoic metamorphism and tectonic evolution of the lower crust of Shakhdara dome,Pamir Mountains

作　　者：李羿芃[1] 丁林[1] 刘德亮[1] OimahmadovIlhomjon MustafoGadoev NegmatRajabov 李顺[1] 

机构地区：[1]中国科学院青藏高原研究所,北京100101 [2]塔吉克斯坦共和国科学院地质地震工程与地震学研究所杜尚别

出　　处：《地质科学》2013年第2期468-483,共16页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国科学院资环局国际合作项目(编号:KZCX2-YW-GJ05);中国科学院战略性先导科技专项(编号:XDB05010400);国家重点基础研究发展计划“973”项目(编号:2011CB403101)资助

摘　　要：帕米尔高原从西到东展布的8个新生代变质穹窿构成帕米尔高原变质地壳的主体，沙克达拉穹窿是其中最大的一个。沙克达拉穹窿变质杂岩中石榴矽线石片麻岩峰期组合（Grt＋Ky＋Bi＋Rt＋Pl＋Qz）变质作用温压条件为丁约810oC／P约10kbar；石榴石单斜辉石基性麻粒岩峰期组合（Grt＋cpx＋RI＋Pl＋Qz）变质作用温压条件为r约824℃／P约16．3kbar；榴闪岩退变较强，其残留峰期组合（Grt＋Pl＋Hbl＋ilm＋Qz）变质作用温压条件为r，约683℃～873oC／P约8．6～11．7kbar。基性麻粒岩变质锆石的u—Pb年龄为19～35Ma，反映了从晚始新世到早中新世帕米尔高原下地壳加热加厚过程。帕米尔穹窿的变质作用可以与高喜马拉雅结晶岩系类比，在新生代印度亚洲大陆碰撞过程中，帕米尔陆内各地体沿前新生代缝合带的陆内俯冲可能是帕米尔下地壳加厚的主要动因。Pamir metamorphic crust is dominated by eight metamorphic domes exposed across Pamir from east to west, among which Shakhdara dome is the biggest one. Peak T-P condition of Shakhdara garnet-sillimanite gneiss is T - 810 ℃/P - 10kbar represented by its peak assemblage Grt＋Ky ＋ Bi ＋ Rt ＋ P1 ＋ Qz, while the peak T-P condition undergone in Shakhdara＇s garnet-clinopyroxene granulite is T - 824 ℃/P - 16.3kbar calculated from the peak assemblage Grt ＋ Cpx ＋ Rt ＋ P1 ＋ Qz. As to garnet-amphibolites in Shakhdara, which had experienced relatively severe retrograde, T - 683 ℃ - 873 ℃/P - 8.6 - 11.7kbar is revealed as the metamorphism condition of its residual peak assemblage Grt ＋ P1 ＋ Hbl ＋ ilm ＋ Qz. Peak metamorphic age 19 - 35 Ma of the mafic granulites dated by U-Pb method on zircons may reflect the thickening and heating process of Pamir lower crust from Late Eocene to Early Miocene. The metamorphism of Pamir domes could be compared with that of High Himalaya crystalline complex and we suggest that Cenozoic Pamir intra-continental-subduction alone the formerly formed suture zone after India-Asia Collision could be the trigger of Cenozoic thickening and metamorphism of lower crust in Pamir.

关 键 词：帕米尔穹窿 下地壳 新生代变质作用 陆内俯冲 

分 类 号：P542[天文地球—构造地质学] P588[天文地球—地质学]