滇东成冰纪南沱组碎屑锆石U-Pb年代学研究及其地质意义  

STUDY OF DETRITAL ZIRCON U-Pb AGE OF THE CRYGENIAN NANTUO FORMATION IN EASTERN YUNNAN PROVINCE AND ITS GEOLOGICAL SIGNIFICANCE

作　　者：江卓斐[1,2] 崔晓庄[1,2,3] 伍皓[1,2] 卓皆文[1,2] 王剑[1,2] 熊国庆[1,2] 陆俊泽[1,2] 蔡娟娟[4] JIANG Zhuofei1,2, CUI Xiaozhuang1,2,3, WU Hao1,2, WANG Jian1,2 , XIONG Guoqing1,2 , LU Junzhe1,2 , CAI Juanjuan4(1. Chengdu Center, China Geological Survey ,Chengdu 610081,China; 2. Key Laboratory for Sedimentary Basin and Oil and Gas Resources, Ministry of Land and Resources,Chengdu 610081,China Institute of Sedimentary Geology, Chengdu University of Technology ,Chengdu 610059,China 4. Graduate School of Chinese Academy of Geological Sciences ,Beijing 100037,Chin)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]国土资源部沉积盆地与油气资源重点实验室,四川成都610081 [3]成都理工大学沉积地质研究院,四川成都610059 [4]中国地质科学院研究生院,北京100037

出　　处：《矿物岩石》2018年第1期42-54,共13页Mineralogy and Petrology

基　　金：国家自然科学基金项目(41502114;41402103;41672112);中国地质调查局项目(DD20160017)

摘　　要：针对滇东峨山和澄江新元古代晚期成冰纪南沱组碎屑锆石LA-ICP-MS U-Pb年代学研究的测试结果显示:峨山小街南沱组下段底部冰川杂砾岩最年轻碎屑锆石^(206)Pb/238 U年龄为725 Ma±4 Ma(Th/U=1.4,谐和度=98%);峨山小街南沱组上段底部泻湖相泥质粉砂岩最年轻碎屑锆石206Pb/238 U年龄为665 Ma±4 Ma(Th/U=1.9,谐和度=98%);澄江大飞田南沱组下段底部冰川杂砾岩最年轻碎屑锆石206Pb/238 U年龄为728Ma±4 Ma(Th/U=1.7,谐和度=98%)。采用单颗最年轻碎屑锆石U-Pb年龄定年法(YSG)定年可知,南沱组下段底部沉积时间可能晚于或等于725 Ma±4 Ma,上段底部沉积时间可能晚于或等于665Ma±4Ma,与扬子东南缘长安冰期(Sturtian)和富禄间冰期启动时间相近。沉积年龄下限和沉积特征分析表明,滇东南沱组下段可能与扬子东南缘早冰期长安组对比,而滇东南沱组上段则可能与扬子东南缘间冰期富禄组、大塘坡组对比。碎屑锆石U-Pb年龄谱显示,滇东南沱组碎屑锆石U-Pb年龄谱清晰记录了Rodinia超大陆裂解过程的构造—岩浆热事件,其中ca.850 Ma代表超级地幔柱上涌,ca.820 Ma代表裂谷盆地开启,ca.800 Ma代表裂谷盆地强烈扩张。The detrital zircon U-Pb chronology by LA-ICP-MS is carried out on the Neoprotero- zoic Crygenian Nantuo Formation in Eshan County and Chengjiang County, eastern Yunnan Prov- ince. It shows that the youngest detrital zircon 206Pb/238U age is 725 Ma±4 Ma （Th/U= 1.4, concordance degree=98%） at the bottom of the lower Member of the Nantuo Formation glacial diamictite in Xiaojie of Eshan County,665 Ma±4 Ma （Th/U=1. 9,concordance degree = 98%） at the bottom of the upper Member of the Nantuo Formation lagoon muddy siltstone,and 728 Ma ±4 Ma （Th/U= 1.7, concordance degree = 98%） at the bottom of the lower Member of the Na- ntuo Formation glacial diamictite in Feidatian of Chengjiang County, respectively. According to single youngest zircon U-Pb age dating method （YSG）, the deposition time of the bottom of the lower Member of the Nantuo Formation may be later than or equal to 725 Ma±4 Ma,and the deposition time of the bottom of the upper Member of the Nantuo Formation may be later than or equal to 665 Ma±4 Ma,close to the onset times of the Chang＇an Glaciation （Sturtian） and Fulu Interglaciation in southeastern Yangtze Block. The maximum ages and deposition characteristics indicate that the lower Member of the Nantuo Formation in eastern Yunnan Province may be cor- related to the early glacial Chang＇ an Formation in southeastern Yangtze Block and the upper Member of the Nantuo Formation in eastern Yunnan Province to the interglacial Fulu Formation and Datangpo Formation in southeastern Yangtze Block. The detrital zircon U-Pb age spectrums have distinctly recorded the tectonic-magmatic thermal events of the breakup of the Rodinia Sup- per Continent. Of the detrical zircon U-Pb ages, ca. 850 Ma may be the record of the supper mantle plum upwelling, ca. 820 Ma may be the record of the opening of the rift basins,and ca. 800 Ma may be the record of the strong expansion of rift basins.

关 键 词：滇东 南沱组 锆石U-PB年龄 冰期 间冰期 

分 类 号：P597.3[天文地球—地球化学]