琼东南盆地花岗质岩浆-构造演化及其对潜山储层物性的约束  

Granitic magmatism and tectonic evolution in Qiongdongnan basin and their constraints on the properties of buried hill reservoirs

作　　者：胡林 熊富浩 陈安清[2] 周杰 王文博 侯明才[2] HU Lin;XIONG Fuhao;CHEN Anqing;ZHOU Jie;WANG Wenbo;HOU Mingcai(OOC China Limited,Hainan Branch,Haikou 570311,Hainan,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,Sichuan,China)

机构地区：[1]中海石油(中国)有限公司海南分公司,海南海口570311 [2]油气藏地质及开发工程全国重点实验室,成都理工大学,四川成都610059

出　　处：《地质通报》2024年第7期1191-1206,共16页Geological Bulletin of China

基　　金：中海石油(中国)有限公司海南分公司科技项目《南海西部近海大中型天然气田勘探潜力与突破方向》(编号:KJZH-2021-0003-02)、《琼东南盆地中生界潜山岩性与地层厘定》(编号:CCL2021HNFN0242)和《琼东南盆地中生界潜山优质储层形成机理与储层发育模式》(编号:CCL2021HNFN0248)。

摘　　要：琼东南盆地中生代潜山是认识南海西部陆缘构造演化过程的重要窗口。以琼东南盆地陵南与松南低凸起区的花岗岩潜山为研究对象,开展岩心样品的岩相学、年代学与地球化学研究,揭示其岩石成因及构造环境。研究结果表明,陵南低凸起基岩主要为二长花岗岩,松南低凸起基岩为花岗闪长岩与二长花岗岩。LA-ICP-MS锆石U-Pb年龄揭示,陵南低凸起区花岗岩类分别形成于249 Ma和233 Ma,而松南低凸起区花岗岩类形成于222~219 Ma。陵南低凸起区花岗岩类的铝饱和指数(A/CNK)为0.99~1.16,岩石整体富集Rb、Th、U等大离子亲石元素,亏损Ta、Nb、Ti等高场强元素,属于弱过铝质高钾钙碱性I型花岗岩;松南低凸起区花岗岩类富碱(K_(2)O+Na_(2)O=6.74%~8.41%)、贫铝(Al_(2)O_(3)=12.52%~13.70%),具有较高的Rb/Sr值(2.03~9.20)和10000 Ga/Al值(>6),且岩石富集轻稀土元素,并具明显的负Eu异常,属于典型的A型花岗岩。岩石成因分析表明,琼东南盆地三叠纪花岗岩类起源于变沉积岩的部分熔融,且经历了不同程度的壳幔混合作用和分离结晶作用。琼东南盆地早三叠世花岗岩类形成于古特提斯域的俯冲汇聚和同碰撞环境,而晚三叠世花岗岩类形成于碰撞后伸展背景。琼东南盆地早三叠世花岗岩不仅含有较高比例的长英质脆性矿物,同时经历了俯冲碰撞-碰撞后伸展等多期次构造作用改造,具备形成裂缝型潜山储层的物质基础和构造动力学条件,是南海潜山油气勘探的重要对象。The Mesozoic buried hill in Qiongdongnan basin is an important window to understand the tectonic evolution of the western continental margin of the South China Sea.This paper presents systematic petrographic,geochronological and geochemical studies on the granite buried hills of Lingnan low uplift and Songnan low uplift in the Qiongdongnan basin,aiming to reveal their petrogenesis and tectonic environment.The results showed that the buried hill in Lingnan low uplift(L321-a and L281-a)is mainly comprised by monzogranite,while those in Songnan low uplift(Y83-a and Y83-b)are mainly composed of granodiorite and monzogranite.Zircon U-Pb dating show that the studied granitoids in Lingnan low uplift were formed at 249 Ma and 233 Ma,while those in Songnan low uplift were formed in 222~219 Ma.Petrogeochemical study shows that the A/CNK values of the granitoids in Lingnan low uplift range from 1.04 to 1.15.They are generally enriched in large ion lithophile elements such as Rb,Th and U,and depleted in high field strength elements such as Ta,Nb and Ti,belonging to weakly peraluminous,high potassium calc-alkali I-type granite.The granitoids in Songnan low uplift have high contents of alkali(K_(2)O+Na_(2)O=6.74%~8.41%),but low contents of aluminum(Al_(2)O_(3)=12.52%~13.70%)with high ratios of Rb/Sr(2.03~9.20)and 10000 Ga/Al(>6).They are enriched in light rare earth elements with weak negative Eu anomalies,resembling typical A-type granite.Petrogenesis study shows that the Triassic granitoids in the Qiongdongnan basin are derived by partial melting of sedimentary rocks,followed by different degrees of crust-mantle mixing and fractional crystallization.This study reveals that the Early Triassic granitoids in the Qiongdongnan basin were formed in a convergence and syn-collisional setting during the Paleo-Tethyan subduction,while the Late Triassic granitoids were formed in a post-collision extensional setting.The large-scale Early Triassic granitoids in the Qiongdongnan basin not only contains a high proportion of felsic brittle

关 键 词：琼东南盆地 花岗岩类 潜山 锆石U-PB年龄 构造环境 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]