南黄海中-新生代裂谷盆地构造-热演化:对成盆机制和烃源岩热演化的指示  

Tectonic-Thermal Evolution of Meso-Cenozoic Rift Basin in South Yellow Sea,Offshore Eastern China:Implications for Basin-Forming Mechanism and Thermal Evolution of Source Rocks

作　　者：李志强 杨波 韩自军 黄振 吴庆勋 Li Zhiqiang;Yang Bo;Han Zijun;Huang Zhen;Wu Qingxun(Tianjin Branch of China National Offshore Oil Corporation,Tianjin 300459,China)

机构地区：[1]中海石油(中国)有限公司天津分公司,天津300459

出　　处：《地球科学》2022年第5期1652-1668,共17页Earth Science

基　　金：国家科技重大专项“中国近海富烃凹陷优选与有利勘探方向预测”(No.2016ZX05024-002)。

摘　　要：基于Advanced McKenzie地球动力学模型和Easy%RoDL化学动力学模型,建立了南黄海中-新生代(K13-Q)裂谷盆地的构造-热演化史,结合盆地深部壳幔结构、梳理周缘中-新生代板块汇聚与离散过程,讨论了该盆地低地热状态成因、成盆机制和烃源岩热演化.盆地地壳伸展系数约为1.22,岩石圈地幔伸展系数约为1.06;由裂陷期(K13-E2)至今,最高热流值仅由约76 mW/m^(2)降低至约66 mW/m^(2),最高地温梯度仅由约37℃/km降低至约30℃/km,首次揭示低地热状态贯穿整个裂谷盆地发育阶段.低岩石圈地幔伸展系数、深部非镜像莫霍面分布、盆地发育阶段仅处于弧后远场拉张应力环境,均指示成盆过程中深部伸展上涌强度低,是导致其持续低地热状态的根本原因,深部热应力不是其主要成盆动力来源;依据高地壳伸展系数和控盆拆离断层演化,认为印支-燕山期先存逆冲断裂复活形成壳间拆离体系,并以简单剪切变形方式控制裂谷盆地发育,是其根本成盆机制;南、北部坳陷烃源岩主排烃期为三垛组二段沉积时期,自渐新世构造反转后热演化终止,古埋深和古地温场条件共同控制现今南、北部坳陷相同深度烃源岩热成熟度差异.The tectonic-thermal evolution history of the Meso-Cenozoic rift basin in the South Yellow Sea is established by using Advanced McKenzie geodynamic model and Easy% RoDL chemical kinetic model, combined with the deep crust and lithospheric mantle structure of the basin, the process of Meso-Cenozoic plate convergence and dispersion around the basin is analyzed. In addition,the genesis of low geothermal state, basin-forming mechanism and thermal evolution of source rocks in the basin are discussed. The results show that the crustal extension coefficient is of about 1.22 and the lithospheric mantle extension coefficient is of about 1.06. From the rift period to the present, the maximum heat flow value only decreased from 76 mW/m^(2) to66 mW/m^(2), and the maximum geothermal gradient only decreased from 37 ℃/km to 30 ℃/km. It is revealed that the low geothermal state runs through the whole rift basin development stage for the first time. Low lithospheric mantle extension coefficient, deep non-mirror Moho distribution, the development stage of the basin are only in the far field tensile stress environment behind the arc,all indicate that the low intensity of lithospheric mantle extension and asthenosphere upwelling is low that is the fundamental reason for the continuous low geothermal state of the basin, and the deep thermal stress is not the main power source of the basin formation. According to the high crustal extension coefficient and the evolution of the detachment fault, it is suggested that the Indosinian and Yanshanian thrust fault regenerated to form the intra-crustal detachment system, and controlled the development of rift basin by simple shear deformation, which is the basic basinforming mechanism. The main oil expulsion of the source rocks in the southern and northern depressions is the sedimentary period of the second member of the Sanduo Formation, and the thermal evolution of the source rocks ended since the Oligocene tectonic inversion. Paleo-buried depth and paleo-geothermal field jointly control

关 键 词：盆地动力学 裂谷盆地 构造-热演化 盆地热状态 成盆机制 烃源岩热演化 南黄海盆地 油气地质 

分 类 号：P541[天文地球—构造地质学]