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华北克拉通南缘栾川群的形成时代、物源及其对区域构造演化的意义:锆石U-Pb年代学和Hf同位素制约
投稿时间:2019-01-17  修订日期:2019-03-19  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2019153
摘要点击次数: 126
全文下载次数: 136
作者单位E-mail
李振生 合肥工业大学资源与环境工程学院 lizhensh@163.com 
贾 超 合肥工业大学资源与环境工程学院  
赵卓娅 合肥工业大学资源与环境工程学院  
霍金晶 合肥工业大学资源与环境工程学院  
李全忠 合肥工业大学资源与环境工程学院 liqzhong@hfut.edu.cn 
张交东 中国地质调查局油气资源调查中心  
中文摘要:栾川群沿秦岭造山带和华北克拉通两大构造单元的结合部分布,其时代归属和构造意义长期存在争议。本文从锆石U-Pb年代学和Hf同位素角度对栾川群进行物源分析和区域对比分析,为合理地理解华北克拉通南缘晚前寒武纪构造演化提供重要证据。栾川群上部大红口组浅变质粗面岩的结晶年龄为854±8Ma,成因以古元古代晚期陆壳物质的再循环或改造为主。栾川地区栾川群变碎屑岩中最年轻的碎屑锆石U-Pb年龄和大红口组浅变质粗面岩及相关侵入岩的结晶年龄限定栾川群沉积时代在917~844 Ma,属于新元古代青白口纪。栾川群白术沟组中上部至鱼库组变碎屑岩的碎屑锆石U-Pb年龄和Hf同位素特征一致,碎屑锆石U-Pb年龄集中在1.85~1.10 Ga之间,北秦岭地体是最可能的物源区;Hf两阶段模式年龄(TDM2)为1.33~2.92 Ga,揭示源区经历了~1.45Ga、~1.8Ga、~2.1Ga和~2.5Ga四期元古代陆壳增生。栾川群白术沟组下部和白术沟组中上部至鱼库组地层间截然不同的碎屑锆石年龄谱图表明白术沟组沉积期间物源区由华北克拉通转变为北秦岭块体,沉积构造背景由被动大陆边缘转化为碰撞造山和后碰撞伸展环境。北秦岭地体原来应属于华北克拉通的一部分,至少在华北克拉通南缘至东缘地区曾存在与北秦岭地体类似的中、新元古代构造带。该构造带强烈地参与了Columbia超大陆裂解和Rodinia超大陆汇聚及裂解过程,在新元古代早期与华北克拉通曾短暂的拼合并造山,转变为华北克拉通周缘沉积盆地的主要物源供给区。
中文关键词:栾川群  物源分析  晚前寒武纪  北秦岭  华北克拉通  地壳增生历史
 
Depositional age and sedimentary provenance of the Luchuan group in the southern margin of the North China Craton and its significance for regional tectonic evolution: Constraints from zircon U-Pb geochronology and Hf isotope
Author NameAffiliationE-mail
LI Zhensheng School of Resources and Environmental Engineering, Hefei University of Technology lizhensh@163.com 
JIA Chao School of Resources and Environmental Engineering, Hefei University of Technology  
ZHAO Zhuoya School of Resources and Environmental Engineering, Hefei University of Technology  
HUO Jinjing School of Resources and Environmental Engineering, Hefei University of Technology  
LI Quanzhong School of Resources and Environmental Engineering, Hefei University of Technology liqzhong@hfut.edu.cn 
ZHANG Jiaodong Oil Gas Resources Survey Center of CGS  
Abstract:There is a long-standing controversy about depositional age and tectonic significance of Luanchuan Group, which locates joint part of two tectonic units of Qinling orogenic belt and North China Craton (NCC). In this paper, the provenance and regional comparative analysis of Luanchuan Group from the perspective of zircon U-Pb chronology and Hf isotope could provide important evidence of late Precambrian tectonic evolution in the southern margin of NCC. The crystallization age of epi-metamorphic trachyte from Dahongkou Formation in the upper part of the Luanchuan Group is 854 ± 8 Ma, and its genesis is mainly due to the recycling of Late Paleoproterozoic continental crust. The depositional age of Luanchuan Group is limited in 917 to 844 Ma by the youngest clastic zircon U-Pb age of metaclastic rocks of Luanchuan Group in Luanchuan area and crystallization age of epi-metamorphic trachyte of Dahongkou Formation and related intrusive rocks, which belongs to Neoproterozoic Qingbaikou Period. There are similar U-Pb age and two-stage Hf model age (TDM2) of detrital zircons among the clastic rocks from Luanchuan Group in Luanchuan area, which consist of upper and middle parts of Baishugou Formation to Yuku Formation, the former are mostly between 1.85 and 1.10 Ga, whose most probable provenance is North Qinling terrane (NQT), and the latter are between 1.33 and 2.92 Ga, which indicates that the provenance area has undergone 4 times of Proterozoic crustal accretion of ~1.45 Ga, ~1.8 Ga, ~2.1 Ga and ~2.5 Ga. The conversion of the provenance of Luanchuan Group from NCC to NQT and its sedimentary tectonic setting from passive continental margin to collisional orogeny and post-collisional extension environment during sedimentation of baishugou Formation are suggested by marked difference of detrital zircon age spectrum between lower parts of Baishugou Formation and other strata of Luchuan Group. NQT would belong to a part of NCC, and a Meso-Neoproterozoic tectonic belt similar to NQT developed at least in eastern and northern margin of NCC. The tectonic belt was strongly involved in process of Columbia supercontinent breakup and Rodinia supercontinent convergence, and was briefly combined with NCC during early Neoproterozoic era to transform into the main provenance supply area of peripheral sedimentary basin of NCC.
keywords:Luchan Group  provenance analysis  Late Precambrian  Northern Qinling  North China Craton  history of crustal growth
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