南海北部陆缘大陆架科学钻探选址:珠江口盆地沉积源汇启示  

Scientific drilling sites of the northern South China Sea margin:insights fromsediment source-to-sink in the Pearl River Mouth basin

作　　者：刘仲强 索艳慧[1,2] 杜晓东 蔡国富 程昊皞 王光增 周洁 刁一笑 付新建 李三忠 Liu Zhongqiang;Suo Yanhui;Du Xiaodong;Cai Guofu;Cheng Haohao;Wang Guangzeng;Zhou Jie;Diao Yixiao;Fu Xinjian;Li Sanzhong(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Laboratory of Submarine Geosciences and Prospecting Techniques,MOE and College of Marine Geosciences,Ocean University of China,Qingdao,Shandong 266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266100,China;Shenzhen Branch,CNOOC China Limited,Shenzhen,Guangdong 518000,China)

机构地区：[1]深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室和中国海洋大学海洋地球科学学院,山东青岛266100 [2]青岛海洋科学与技术国家实验室,海洋矿产资源评价与探测技术功能实验室,山东青岛266100 [3]中海石油(中国)有限公司深圳分公司,广东深圳518000

出　　处：《地质学报》2022年第8期2775-2787,共13页Acta Geologica Sinica

基　　金：中央高校基本科研业务费专项(编号202172003);国家自然科学基金项目(编号91958214,42121005)联合资助的成果。

摘　　要：南海海盆自1998年始开展了一系列大洋科学钻探,取得了重大成就,但揭开南海海盆打开过程的关键记录在南海北部陆缘大陆架。因此,开展南海北部陆缘科学钻探非常必要。珠一坳陷位于南海北部珠江口盆地,不仅具有巨大的油气资源潜力,而且记录了南海海盆打开前的地质背景。该地区的物源特征分析对于揭示物质源汇过程、重建盆地构造演化过程、预测优质储层具有重要指示作用,一直是当前研究的热点,也可从沉积学角度为论证南海大陆架科学钻探选址提供依据。本文采用锆石LA-ICP-MS U-Pb定年技术,结合锆石CL图像及稀土元素配分特征,对珠一坳陷东西两侧典型地区的样品锆石进行了物源示踪、沉积源汇分析,并探讨其物源变化的构造成因。结果表明,下始新统下文昌组沉积期到上始新统上文昌组-下恩平组沉积期,坳陷物源由盆内转换为盆外供应为主。其中,恩平凹陷部分洼陷由于没有文昌组沉积地层,下恩平组仍以盆地内物源供给为主;惠州凹陷和陆丰凹陷则从上文昌组开始转为盆外物源供给。惠州和陆丰地区上始新统恩平组、渐新统珠海组、下中新统珠江组地层锆石自形程度较低,磨圆度较高,边缘破坏较为严重,年龄分布较为分散,稀土元素配分特征与基底不同,说明上文昌组-恩平组地层沉积之后,坳陷主要接受盆外华南板块物源供给。该物源转换与~43 Ma时珠一坳陷裂陷作用自南向北的转换密切相关。Since 1998,a series of ocean scientific drilling has been carried out in the South China Sea basin,and great achievements have been made.However,the key records to uncover the opening mechanism of the South China Sea ocean floor are in the continental shelf on the northern South China Sea margin.Therefore,it is essential to carry out scientific drilling on the continental shelf.The Zhu I depression is an important tectonic unit of the Pearl River Mouth basin in the northern South China Sea margin,which has not only great potential of oil resources,but also some detailed pre-spreading records of the South China Sea ocean floor.The analysis of provenance characteristics in the shelf plays a key role in revealing the source-to-sink processes,reconstructing the tectonic evolutionary process,and predicting the distribution of high-quality reservoirs.It has always been a hot spot of current research,and can also provide a basis for demonstrating the site selection for scientific drilling in the continental shelf of the South China Sea from the perspective of sedimentology.In this paper,zircon LA-ICP-MS U-Pb dating technique,combined with zircon CL images and REE distribution characteristics,has been used to trace the source of zircon samples from typical areas on the East and west sides of the Zhu I depression,analyze the sedimentary source and sink,and discuss the structural origin of the source changes.The results show that from the early Eocene lower Wenchang Formation sedimentary period to the late Eocene upper Wenchang and lower Enping Formation sedimentary period,the material source of the depression changed from within the basin to outside the basin.Among them,the lower Enping Formation is still dominated by the supply of materials in the basin due to the lack of sedimentary strata of Wenchang Formation in some subsags of the Enping sag.The Huizhou sag and the Lufeng sag began to be supplied by off basin sources from the upper Wenchang Formation.The zircon automorphism of the Upper Eocene Enping Formation,the Ol

关 键 词：珠一坳陷 锆石U-PB定年 物源体系 裂陷作用转换 科学钻探 

分 类 号：P756.5[天文地球—海洋科学]