辽东湾海域新元古界长龙山组石英砂岩物源特征及其地质意义  

Characteristics by Provenance of Quartz Sandstone from the Neoproterozoic Changlongshan Formation in the Offshore Liaodong Bay and Its Geological Significance

作　　者：赵子霖 周雪威 李夔洲 郭涛 彭靖松 侯明才[1,2] ZHAO ZiLin;ZHOU XueWei;LI KuiZhou;GUO Tao;PENG JingSong;HOU MingCai(Institute of Sedimentary Geology,Chengdu University of Technology&Key Laboratory of Deep Time Geological Environment Reconstruction and Application,Ministry of Natural Resources,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;Tianjin Branch of CNOOC China Limited,Tianjin 300452,China)

机构地区：[1]成都理工大学沉积地质研究院&深时地理环境重建与应用自然资源部重点实验室,成都610059 [2]油气藏地质及开发工程全国重点实验室(成都理工大学),成都610059 [3]中海石油(中国)有限公司天津分公司,天津300452

出　　处：《沉积学报》2024年第4期1342-1353,共12页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42102141);中国博士后科学基金(2022T150076);中海石油(中国)有限公司科研项目(CCL2014TIXZSS0870);成都理工大学油气藏地质及开发工程国家重点实验室项目(40200-02021301)。

摘　　要：【目的】渤海辽东湾海域西南部钻井钻遇新元古界青白口系长龙山组石英砂岩,深入研究其物源特征,对华北克拉通太古代至元古代重大地质事件解剖具有重大意义。【方法】对采自BD4-1a井2482 m附近的五件石英砂岩样品进行了全岩地球化学和碎屑锆石U-Pb年代学分析。【结果】全岩地球化学分析结果显示该石英砂岩具有较高的SiO2含量(88.53%~93.06%),化学蚀变指数(CIA)值介于69.5~71.6,成分变异指数(ICV)值介于0.69~3.99,样品表现为高成分成熟度和结构成熟度、中等风化。Th/U值介于3.46~4.92,Cr/Zr值介于0.17~0.35,ΣREE值介于(8.26~24.12)×10^(-6),LREE/HREE值介于6.28~10.21,δEu值介于0.77~1.04,呈弱负异常。碎屑锆石U-Pb年龄分布于2744~1581 Ma,主要年龄峰值为~1845 Ma,次要年龄峰值为~2225 Ma、~2340 Ma、~2600 Ma和~2725 Ma。【结论】全岩地球化学分析结果显示其物源主要来自于上地壳长英质岩石。2.7~2.5 Ga的碎屑锆石是华北克拉通陆壳生长事件及构造热事件形成的记录;2.2~1.8 Ga的碎屑锆石与华北克拉通东部陆块和西部陆块拼合形成同一结晶基底事件的时间相吻合,是哥伦比亚超大陆聚合事件的地质记录;而1.8~1.6 Ga的碎屑锆石年龄记录的应该是哥伦比亚超大陆裂解事件。[Objective]The quartz sandstone of the Changlongshan Formation in the Qingbaikou system from the Neoproterozoic was encountered during drilling in the southwestern Liaodong Bay,Bohai Sea.The in-depth study of its provenance characteristics is of great significance to the anatomy of major geological events from the Archean to Proterozoic in the North China Craton.[Methods]Five quartz sandstone samples collected from around 2482 meters in well BD4-1a were analyzed for whole-rock geochemistry and detrital zircon U-Pb geochronology.[Results]The quartz sandstones had high SiO2 content(88.53%-93.06%),the chemical index of alteration(CIA)value was 69.5~71.6,the index of compositional variability(ICV)value was 0.69-3.99,and the samples displayed high composition⁃al maturity,structural maturity,and moderate weathering.The Th/U ratio ranged from 3.46-4.92,the Cr/Zr ratio of 0.17~0.35.The sum of the rare earth elements(ΣREE)is(8.26-24.12)×10^(-6),the low/heavy rare earth element ratio(LREE/HREE)was 6.28~10.21,and theδEu was 0.77-1.04,which shows a weak negative anomaly.The U-Pb ages of detrital zircons ranged from 2744-1581 Ma;the main age peak was~1845 Ma,and the subordinate age peaks were~2225,~2340,~2600,~2725 Ma,respectively.[Conclusions]Whole-rock geochemistry indicates that the provenance mainly comes from felsic rocks of the upper crust.The 2.7-2.5 Ga detrital zircons record the growth and tectonothermal events of the continental crust in the North China Craton.The 2.2-1.8 Ga detrital zircons correspond to the crystalline basement formation during the amalgamation of the eastern and western blocks of the North China Craton,recording the geological events of the Columbia supercontinent's assembly.The 1.8-1.6 Ga detrital zircon ages likely record the breakup of the Columbia supercontinent.

关 键 词：渤海 碎屑锆石 地球化学 物源 哥伦比亚超大陆 

分 类 号：P597[天文地球—地球化学]