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阿尔金南缘冰沟南组火山岩锆石U-Pb年龄及其前寒武纪构造演化意义
投稿时间:2018-05-16  修订日期:2018-10-22  点此下载全文
引用本文:曾忠诚,边小卫,赵江林,刘向东,张若愚,李琦,何元方,菅坤坤.2019.阿尔金南缘冰沟南组火山岩锆石U-Pb年龄及其前寒武纪构造演化意义[J].地质论评,65(1):103-118,[DOI]:.
ZENG Zhongcheng,BIAN Xiaowei,ZHAO Jianglin,LIU Xiangdong,ZHANG Ruoyu,LI Qi,HE Yuanfang,JIAN Kunkun.2019.U- Pb Geochronology of Zircons from the Volcanic Rocks in Bingounan Formation, Southern Altyn Tagh: Implication for the Precambrian Tectonic Evolution[J].Geological Review,65(1):103-118.
DOI:10.16509/j.georeview.2019.01.008
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作者单位E-mail
曾忠诚 1)陕西省矿产地质调查中心西安7100683)陕西省地质调查院西安710054 113191186@qq.com 
边小卫 1)陕西省矿产地质调查中心西安7100683)陕西省地质调查院西安710054  
赵江林 1)陕西省矿产地质调查中心西安7100683)陕西省地质调查院西安710054  
刘向东 2)陕西省水工环地质调查中心西安7100683)陕西省地质调查院西安710054  
张若愚 2)陕西省水工环地质调查中心西安7100683)陕西省地质调查院西安710054  
李琦 1)陕西省矿产地质调查中心西安7100683)陕西省地质调查院西安710054  
何元方 1)陕西省矿产地质调查中心西安7100683)陕西省地质调查院西安710054  
菅坤坤 1)陕西省矿产地质调查中心西安7100683)陕西省地质调查院西安710054  
基金项目:注: 本文为中国地质调查局地质调查项目(编号:12120114081901、1212011120533)的成果。
中文摘要:在阿尔金南缘玉苏普阿勒克塔格北侧出露的冰沟组火山岩为一套与滨浅海相细粒陆源碎屑岩和碳酸盐岩共生的中基性火山岩,主要岩石类型有蚀变熔结凝灰岩、安山质凝灰熔岩和强蚀变玄武安山岩。该火山岩作为Columbia超大陆裂解阶段的物质记录,对其年代学和产出的地质构造背景的探讨,有助于探讨阿尔金南缘前寒武纪构造演化过程。LA-ICP-MS锆石U-Pb同位素年代学研究结果显示,强蚀变玄武安山岩样品具有两组锆石年龄,第一组年龄分别为944.7±6.4 Ma(n=8,MSWD=0.057)和951.2±6.3 Ma(n=12,MSWD=0.042),测点位于锆石震荡环带上,显示了典型的岩浆锆石的特征,代表火山岩的形成时代,属青白口纪早期;第二组年龄介于446±5~458±4 Ma,与区域高压—超高压岩石的原岩的退变质时代(~450 Ma)一致,可能代表受该期陆壳深俯冲/折返事件改造。另外,228±6 Ma、229±4 Ma和130±1 Ma的年龄信息,可能代表火山岩还遭受了晚三叠世和早白垩世构造热事件改造。构造背景分析表明,该火山岩形成于板内裂谷环境,对应于Columbia超大陆裂解阶段的晚期,之后索尔库里群沉积盆地由拉张转换到汇聚的构造背景,转为Rodinia 超大陆汇聚阶段。结合区域地质特征和该火山岩年龄信息,进一步制约了阿尔金南缘Columbia超大陆裂解和Rodinia 超大陆汇聚的时限分别为945~1602 Ma和871~945 Ma。
中文关键词:阿尔金南缘  冰沟南组  火山岩  锆石U-Pb定年  前寒武纪构造演化
 
U- Pb Geochronology of Zircons from the Volcanic Rocks in Bingounan Formation, Southern Altyn Tagh: Implication for the Precambrian Tectonic Evolution
NameInstitution
ZENG Zhongcheng1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
BIAN Xiaowei1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
ZHAO Jianglin1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
LIU Xiangdong1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
ZHANG Ruoyu2)Shaanxi Hydrogeology Environmental Geology and Engineering Geology Survey Center, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
LI Qi1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
HE Yuanfang1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
JIAN Kunkun1)Shaanxi Mineral Resources and Geological Survey, Xi’an, 710068;3)Shaanxi Institute of Geological Survey, Xi’an, 710054
Abstract:Objectives: Outcropping along the northern flank of Yusupualeketage, southern Altyn Tagh, the intermediate—basic volcanic rocks in Bingounan Formation are characterized by an assemblage of offshore marine fine grained terrigenous clastic rocks and carbonate rocks. This rock assemblage mainly consists of altered ignimbrite, andesitic tuff—lava and strongly altered basaltic andesite. Given that this rock assemblage records the break up of the Columbia supercontinent, it is essential to carry out geochronology study and tectonic analysis for a better understanding of the Precambrian tectonic evolution of the southern Altyn Tagh. Methods: On the basis of detailed field geological survey, we performed the petrology and the zircon U Pb dating of two strongly altered basaltic andesite samples from the volcanic rocks in Bingounan Formation, southern Altyn Tagh. Results: Zircon U-Pb dating (LA-ICP-MS) of both two samples yield two age groups, respectively. The first age groups show peak at 944.7 ± 6.4 Ma (n = 8, MSWD = 0.057) and 951.2±6.3 Ma (n = 12, MSWD = 0.042), respectively. Given that all of the 20 analyzed points locates on the oscillatory zoning of zircon, indicative of typical magmatic zircon feature, we interpret these volcanic rocks formed during early Qingbaikou Period. In terms of the second age group, zircon U Pb age ranges from 446 ± 5 Ma to 458 ± 4 Ma. Considering the second age group is coeval with the retrograde metamorphism of the protolith (~450 Ma) in this high pressure and ultrahigh pressure metamorphic belt, it shows that the volcanic rocks was affected by the event of deep subduction of continental crust and related exhumation process. In addition, we also obtained three age information of 228±6 Ma, 229±4 Ma and 130±1 Ma, which indicates that volcanic rocks have been transformed by Structural—thermal event in the late Triassic and early Cretaceous. Conclusions: In light of tectonic analysis, we suggest these volcanic rocks probably formed in a continental rift corresponding to the late- stage of the break- up of Columbia supercontinent. Then sedimentary basin filled with Suoerkuli Group evolved from transtension to converged setting during which Rodinia supercontinent convergence initiated. Combined with the regional geology and the age from the volcanic rocks in Bingounan Formation, We limit the Precambrian tectonic evolution stage of the southern Altyn Tagh: ① Break up of Columbia supercontinent during Jixianian to early Qingbaikou Period (945~1602Ma); ② Convergence of Rodinia supercontinent during the middle Qingbaikou Period (871~945 Ma).
keywords:southern Altyn Tagh  Binggounan formation  volcanic rocks  zircon U- Pb geochronology  Precambrian tectonic evolution
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