川西新元古代苏雄组层型剖面SHRIMP锆石U-Pb年龄及其地质意义  

SHRIMP Zircon U-Pb Ages for the Stratotype Section of Neoproterozoic Suxiong Formation in Western Sichuan Province and Their Geological Significance

作　　者：卓皆文[1,2] 江卓斐[1,2] 江新胜[1,2] 王剑[1,2] 蔡娟娟[3] 熊国庆[1,2] 陆俊泽[1,2] 崔晓庄[1,2] 刘建辉[4] 

机构地区：[1]中国地质调查局成都地质调查中心,成都610081 [2]国土资源部沉积盆地与油气资源重点实验室,成都610081 [3]中国地质科学院研究生部,北京100037 [4]北京离子探针中心,北京102206

出　　处：《地质论评》2017年第1期177-188,共12页Geological Review

基　　金：国家自然科学基金资助项目(编号:41672112;41030315;41502114);中国地质调查局项目(编号:DD20160017;12120114067901;1212011121105)的成果~~

摘　　要：对采自川西新元古代苏雄组层型剖面中上部的英安岩进行SHRIMP锆石U-Pb定年,获得了两组谐和年龄值:838±9 Ma(n=9,MSWD=0.80)和780±12Ma(n=5,MSWD=1.2)。其中780±12 Ma解释为苏雄组英安岩的喷发时限,代表康滇裂谷盆地强烈扩张时期的构造岩浆热事件;而838±9 Ma则可能代表康滇裂谷盆地开启前的构造岩浆热事件。综合研究认为,苏雄组位于康滇裂谷半地堑盆地的调节带,为华南新元古代幕式岩浆活动的产物;火山活动和沉积记录均表明,扬子周缘发育与地幔柱相关的裂谷盆地系统,且华南可能是Rodinia超大陆裂解的重要组成单元。Objectives： The age and tectonic setting of extensive Neoproterozoic volcanic activities around the margin of Yangtze Block were of great significance for reconstructing the position of South China Block in the Rodinia supereontinent. At present, only a few precise ages were obtained from the volcaniclastics of Suxiong Formation in the western margin of Yangtze Block. Therefore, a dacite sample for the stratoype section was collected from Suxiong Formation, with the purpose of determinating the high-precise age in western Sichuan province. Methods：The zircon SHRIMP U-Pb analysis was used to determinate the age of the dacite sample from the Suxiong Formation, which was carried out by SHRIMP Ⅱ in Beijing SHRIMP Center, Chinese Academy of Geological Sciences. Results：Two precise ages of 838 ± 9 Ma and 780 ± 12 Ma were obtained. Conclusions：Among them, the younger one, 780 ± 12 Ma, was interpreted as the eruption age of the dacite sample, which could represented the tectonic--magma event of the Kangdian rift basin during the period of strong extension, and the older one, 838 ± 9 Ma, represented the tectonic--magma event before the opening of the Kangdian rift basin. Through the comprehensive analysis, the Suxiong Formation was regarded as the product of episodic magmatic activity, locating at the accommodation zones of the Kangdian half graben. Consequently, a series of rift basins, which were related to the mantle plume that led to the breakup of Rodinia supercontinent, should be developed around the margin of Yangtze Block, while the South China Block could be a member of Rodinia supercontinent breakup, through the analysis of volcanic activities and sedimentary records.

关 键 词：苏雄组 英安岩 SHRIMP锆石U—Pb年龄 新元古代 构造岩浆热事件 

分 类 号：P597.3[天文地球—地球化学] P534.3[天文地球—地质学]