从源到汇:大别造山带物源区与合肥盆地南缘中生代沉积耦合关系——来自碎屑锆石U-Pb年龄证据  

From source to sink: Coupling relation between the Dabie Shan Orogen provenance and Mesozoic sediments of the south-margin of Hefei Basin,based on the evidence of detrital zircon ages

作　　者：李双应[1] 魏星[1] 谢伟 程成[1] 李敏 胡博 柴广路 Li Shuang-Ying;Wei Xing;Xie Wei;Cheng Cheng;Li Min;Hu Bo;Chai Guang-Lu(School of Resources and Environmental Engineering,Hefei Universityof Technology,Hefei 230009,China)

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009

出　　处：《古地理学报》2019年第1期82-106,共25页Journal of Palaeogeography：Chinese Edition

基　　金：国家自然科学基金项目(编号:41772098和41172097);安徽省公益性地质调查项目(编号:2015-g-24)联合资助~~

摘　　要：形成于印支期的大别造山带和周缘中生代盆地构成了一级源汇系统,其中位于造山带北缘的合肥盆地中生代地层发育,且以盆地南缘出露最好,这为盆山源汇系统研究提供了理想的沉积记录。笔者从合肥盆地南缘采集了10个砂岩样品和1个砾岩样品,进行锆石U/Pb (LA-ICP-MS)定年分析,获得了742个有效年龄(置信度不小于85%),范围为113±3. 6-2983 Ma。这些碎屑锆石年龄谱可以被分为5个年龄段:113-137 Ma,峰值131 Ma; 184-273 Ma,峰值226 Ma; 274-517. 3 Ma,具有2个峰值280 Ma和474 Ma; 532-856. 6 Ma,具有3个峰值572 Ma、649 Ma和772 Ma; 1786-2600 Ma,具有2个峰值2035 Ma和2506 Ma。同时,总结了物源区大别造山带不同单元锆石U-Pb年龄特征。根据锆石U/Pb年龄和Th/U值,发现这5个年龄段比较准确地记录了物源区地质体,分别是早白垩世的岩浆岩、大别山高压—超高压变质岩、北淮阳的浅变质岩、北大别的正片麻岩和卢镇关群变质岩。根据锆石最小年龄,修正了合肥盆地南缘中生代地层格架,为源汇系统研究确立了时间框架。合肥盆地南缘中生代沉积可以分为4个演化阶段:晚三叠世瑞替期—早侏罗世辛涅缪斯期、中—晚侏罗世、早白垩世早期和早白垩世晚期,并据此确定了每个阶段主要物源区特征及其时空变化。碎屑锆石U/Pb年龄和Th/U值限定了大别造山带仅存在三叠纪的超高压变质作用,且超高压变质岩折返到地表的最早时间是晚三叠世瑞替期,大别造山带大陆岛弧发育的时间是新元古代。上述研究结果不仅为恢复大别造山带构造古地理做出了新的贡献,而且更为盆山源汇系统研究提供了一个实例。The Dabie Orogen formed in Triassic and its peripheral Mesozoic basins form a source to sink system.The Hefei Basin with well-developed Mesozoic in the north and well-exposed outcrops in the south provides ideal sedimentary records for the investigation of the basin-ridge source to sink system.Ten sandstone and one conglomerate samples were collected for zircon U-Pb(LA-ICP-MS)dating analysis which result in 742 effective ages(confidence level larger or equal to 85%)ranging from 113 Ma to 2983 Ma.The detrital zircon ages can be divided into five age groups,including 113-137 Ma and with a peak of 131 Ma,184-273 Ma and with a peak of 226 Ma,274-517.3 Ma and with two peaks of 280 Ma and 474 Ma,532-856.6 Ma and with three peaks of 572 Ma,649 Ma and 772 Ma,1786-2600 Ma and with two peaks of 2035 Ma and 2506 Ma.Moreover,we summarized the zircon U-Pb age data of various geological terrains from the Dabie Orogen and comparised the data with the aforementioned five age groups.Based on the zircon U/Pb ages and their Th/U ratios,the five age groups correctly correspond to the provenance geological terrains that are respectively Early Cretaceous magma rocks,Dabie Shan HP-UHP metamorphic rocks,north Huaiyang lower-grade metamorphic rocks,north Dabie orthogneiss and Luzhengguan group metamorphic rocks.According to the youngest zircon U-Pb ages,the Mesozoic stratigraphic framework of the south margin of the Hefei Basin is newly amended,which supports a time frame for source to sink system research.Mesozoic sedimentation in the south margin of the Hefei Basin can be divided into four evolutive stages(i.e.,Later Triassic Rhaetian-Early Jurassic Sinemurian,Middle-Later Jurassic,early and Later stages of Early Cretaceous),and major characters and space-time changes of source rocks in each stage also are determined.Detrital zircon U/Pb ages and Th/U ratios suggest that the UHP process happened in the Dabie Orogen to Triassic,not Caledonian or Neoproterozoic.It was in Late Triassic Rhaetian that UHP rocks exhumated and outcropped in s

关 键 词：源汇系统 锆石U-PB定年 中生代 大别造山带 合肥盆地 

分 类 号：P512[天文地球—地质学]