中国北部陆架海碎屑锆石U-Pb年龄和钾长石主微量元素物源示踪研究  

Detrital zircon U-Pb ages and K-feldspar main and trace elements provenance studying from fluvial to marine sediments in northern China

作　　者：林旭 刘静[2] 吴中海 王世梅[1] 赵希涛[4] 陈勇[1] 李兆宁 刘海金 LIN Xu;LIU Jing;WU Zhonghai;WANG Shimei;ZHAO Xitao;CHEN Yong;LI Zhaoning;LIU Haijin(China Three Gorges University,Hubei.443002;Tianjin University,Tianjin,300072;Institute of Geological Mechanics,Chinese Academy of Geological Sciences,Beijing,100081;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029;Institute of Geology,China Earthquake Administration,Beijing,100029;East China University of Technology,Jiangxi,330013)

机构地区：[1]三峡大学,湖北宜昌443002 [2]天津大学,天津300072 [3]地科院地质力学研究所,北京100081 [4]中科院地质与地球物理研究所,北京100029 [5]中国地震局地质研究所,北京100029 [6]东华理工大学,江西南昌330013

出　　处：《地质学报》2020年第10期3024-3035,共12页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41702178,41972212)资助的成果。

摘　　要：渤海湾盆地每年沉积大量的河流碎屑物质,但其中的砂级物质能否迁移扩散到胶东半岛海湾内一直不清楚。锆石和钾长石分别是河流沉积物中常见的副矿物和主要造岩矿物之一,由于各自的U-Pb年龄和地球化学元素组成在不同区域内存在显著差异,是进行物源示踪研究的理想矿物。基于此,本文利用激光剥蚀电感耦合等离子质谱仪(LA-ICP-MS)对渤海湾盆地主要注入河流和胶东半岛的威海湾和银滩湾的海岸砂开展碎屑锆石(n=438)和钾长石(n=160)微区原位U-Pb年龄、Th/U比值和主微量元素分析,结果表明威海湾和银滩湾内的砂级沉积物的碎屑锆石以具有典型的新元古代峰值年龄(697~735 Ma),缺乏古元古代和新太古代峰值年龄为特征,Th/U比值和胶东基岩接近,结合Kolmogorov-Smirnov统计方法的多维判别图(MDS),说明这些砂级碎屑物质的源区主要是以胶东半岛为源区的近源物质。而黄河口的碎屑钾长石原位(in situ)Na2O、K2O、Al2O3和Rb、Sr、Ba、Pb元素含量变化与刘公岛和银滩的海砂样品截然不同,进一步验证了上述碎屑锆石的研究结果。因而将碎屑锆石和钾长石原位地球化学分析相结合有助于精准判定物源关系,在今后中国北部陆架海物源示踪研究、渤海湾盆地盆山耦合研究中将具有良好的应用前景。A large amount of fluvial detrital sediments accumulate in the Bohai Bay Basin each year,however,it is not clear whether the sand-grade grains can migrate and spread to the gulfs of Jiaodong Peninsula,North China.Here we present 438 new concordant detrital zircon U-Pb ages from the Liao,Luan,Yongding,Hutuo,and Zhang rivers,as well as the marine sands from the Liugong Island,Weihai and Yintan bays of Jiaodong Peninsula.We also present a compilation of published bedrock and detrital zircon data from Jiaodong and Korean peninsulas to evaluate potential sediment source regions.The peak ages of zircons in marine sands are characterized by the presence of Neoproterozoic and the absence of Paleoproterozoic and Neoarchean peak ages.Combined with the Th/U rations and MDS plot,we find that the detrital zircons from rivers in the North China Craton and Korean Peninsula are not the main provenance areas for sand-grade grains within the bays of Jiaodong Peninsula.These detrital sand-grade sediments are mainly from local source areas from the Jiaodong Peninsula.We also present 160 new in situ geochemical data on detrital K-feldspar grains from the Yellow River and Weihai and Yintan from the Jiaodong Peninsula to check the above results.By comparing the content change of main elements(NaO,K20,Al203)and trace elements(Rb,Sr,Pb,Ba),it can be clearly found that there are no provenance relationships among them.Therefore,the combination of detrital zircon and K-feldspar in situ geochemical analysis can become a potential provenance tool for studying material spreading in the marginal sea of North China,big river evolution and basin-mountain coupling of Bohai Bay Basin.

关 键 词：渤海 胶东半岛 锆石 U-Pb年龄 钾长石 元素特征 物源示踪 

分 类 号：P597.3[天文地球—地球化学]