攀枝花大田地区康定群咱里组变质杂岩P—T—t轨迹及其构造意义  

The P—T—t path and its tectonic significance for metamorphic complex of the Zanli Formation,Kangding Group,in Datian area,Panzhihua City

作　　者：张宝玲 陈友良[1,2] 欧何琼 付于真[1] 殷桂芹 顾孟娟 ZHANG Baoling;CHEN Youliang;OU Heqiong;FU Yuzhen;YIN Guiqin;GU Mengjuan(College of Earth Sciences,Chengdu University of Technology,Chengdu,610059;Sichuan Key Laboratory of Applied Nuclear Techniques in Geosciences,Chengdu University of Technology,Chengdu,610059)

机构地区：[1]成都理工大学地球科学学院,成都610059 [2]成都理工大学地学与核技术四川省重点实验室,成都610059

出　　处：《地质论评》2023年第3期881-896,共16页Geological Review

基　　金：国家自然科学基金资助项目(编号:42072096);中国核工业地质局重点科研项目“康滇地轴铀成矿环境及选区研究”(编号:202137-3);成都理工大学珠峰科技计划项目(编号:2021ZF11413)的成果。

摘　　要：扬子板块西缘的康定杂岩为一套由侵入岩和变质岩共同组成的岩浆—变质混合杂岩,是研究罗迪尼亚超大陆裂解的重要窗口。长期以来对康定杂岩中的岩浆杂岩研究较多,但对变质杂岩研究较为薄弱。为全面了解康定杂岩形成的构造背景及成因机制,笔者等对扬子板块西缘的攀枝花大田地区康定群咱里组石榴夕线黑云斜长片麻岩进行了详细的岩相学、矿物地球化学、变质P—T条件估算研究,同时对同一层位的石榴二云片岩进行了锆石LA-ICP-MS U-Pb年代学分析。结果表明:石榴夕线黑云斜长片麻岩可识别出三期变质矿物组合:进变质阶段矿物组合(M1)为石榴子石变斑晶核部及其核部包裹体(石榴子石核部+第一期黑云母+第一期夕线石+钛铁矿+石英),P—T条件为609~690℃—0.2~0.3 GPa;峰期变质阶段矿物组合(M2)为石榴子石变斑晶幔部及变基质矿物(石榴子石幔部+第二期黑云母+第二期夕线石+斜长石+石英),P—T条件为643~732℃—0.20~0.51 GPa;退变质阶段矿物组合(M3)为石榴子石变斑晶边部及变基质矿物(石榴子石边部+第二期黑云母+第二期夕线石+斜长石+石英),P—T条件为602~687℃—0.27~0.39 GPa。石榴夕线黑云斜长片麻岩记录了具近等压冷却型(IBC)的逆时针P—T演化轨迹;石榴二云片岩锆石U-Pb定年结果表明区内的变质时代为842±10 Ma,综合分析表明:扬子板块西缘的变质杂岩形成于拉张环境,结合区内的同期岩浆活动特征,认为区内新元古代变质事件可能与超级地幔柱引发的岩浆活动有关。The Kangding complex in the western margin of the Yangtze Plate is a set of magmatic—metamorphic complex composed of intrusive rock and metamorphic rock,which are important window for studying the disintegration of the Rodinian supercontinent.Although numbers of studies focused on magmatic complex,metamorphic rocks within the complex were weakly understood.To comprehensively understand the tectonic setting and genetic mechanism of Kangding complex,this paper selected Zanli Formation of the Kangding Group in Datian of the Panzhihua area,aimed to apply petrological,mineralogical and geochemistry analysis,date garnet—mica schist using zircon U-Pb method and estimating metamorphic P—T condition for garnet—sillimanite—biotite—plagioclase gneiss.Three metamorphic generations indicated by metamorphic mineral assemblages were identified from garnet—sillimanite—biotite—plagioclase gneiss.The prograde mineral assemblage M1 in the core of porphyroblastic garnet has mineral assemblage of garnet(core)+biotite+fibrolite+ilmenite+quartz,which has P—T condition of 609~690℃—0.2~0.3 GPa.The peak metamorphic mineral assemblage M2 is dominantly composed of porphyroblastic garnet(mantle)and the matrix minerals biotite+fibrolite+plagioclase+quartz,revealing P—T condition of 643~732℃—0.20~0.51 GPa.The retrograde metamorphic mineral assemblage M3 is dominantly composed of porphyroblastic garnet(rim)and the matrix minerals biotite+fibrolite+plagioclase+quartz,which has P—T condition of 602~687℃—0.27~0.39 GPa.Thus an anticlockwise P—T path with nearly isobaric cooling(IBC)type was recorded in the garnet—sillimanite—biotite—plagioclase gneiss.Zircons separated from garnet—mica schist were dated at 842±10 Ma,indicating the metamorphic ages in the region.The comprehensive analysis shows that the metamorphic complex in the western margin of the Yangtze Plate was formed in the extensional environment and combined with the characteristics of contemporaneous magmatic activity in the area,it is sugge

关 键 词：大田地区 康定群变质杂岩 逆时针P—T轨迹 变质时代 构造意义 

分 类 号：P588.3[天文地球—岩石学] P597.3[天文地球—地质学]