摘要
热流调查和构造热演化数值模拟是油气地热研究不可或缺的重要内容。沉积盆地在其演化过程中往往叠加了特殊构造事件。通过热流调查和构造热演化数值计算可以更好地约束这些特殊过程,重建更为真实的构造热演化历史。该文通过对南海北部琼东南盆地和珠江口盆地中段热流变化特征分析和构造热演化数值模拟,探讨了影响其热流变化的主要因素。结果表明,琼东南盆地可分3个热流分区:北部陆架与上陆坡区(50~70mW/m^2)、中央坳陷带深水区(70~85mW/m^2)和盆地东部深水区高热流带(>85mW/m^2);珠江口盆地中段从陆架往海盆方向热流呈阶梯式抬高,西江凹陷平均热流为55mW/m^2,番禺低隆起为58mW/m^2,白云凹陷为70mW/m^2,下陆坡区为85mW/m^2;陆坡区高热流不仅与岩石圈强烈减薄相关,而且还受到岩石圈破裂时引起的深部热物质上涌的影响,后者对现今陆坡区还有约20mW/m^2的热流贡献;琼东南盆地东部高热流值则主要受到晚中新世以来的岩体侵位热事件的影响,岩体侵入热事件对现今热流值贡献可达10~25mW/m^2。分析表明,在南海深水盆地开展构造热演化数值计算时,需要考虑沉积过程、海底扩张以及岩浆活动等影响因素。
Heat flow survey and numerical modeling of teetono-thermal evolution are the most important part of geothermal research on oil-gas bearing basins. As normal evolution of a sedimentary basin often overlaps with special tectonic events, heat flow survey and numerical modeling can be helpful to reveal these events and rebuild more reliable tectono-thermal evolution history. This paper analyzes the heat flow variation features in the Qiongdongnan Basin and the middle part of the Pearl River Mouth Basin, and rebuilds the basins＇ thermal histories by numerical modeling, followed by discussions on the main influential factors of the observed thermal variations. The results show that, the Qiongdongnan Basin could be divided geothermally into three regions： the northern shelf and upper slope region, deep-water area in the central depression zone and a NE trending high heat flow zone in the eastern basin, with heat fiows of 50 - 70 mW/m^2 , 70 - 85 mW/m^2 and 〉85 mW/m^2, respectively. Heat flow in the middle part of the Pearl River Mouth Basin shows a seaward stepwise increase from the shelf to the lower slope with average heat flows of 55, 58, 70 and 85 mW/m^2 in the Xijiang sag, Panyu low rise, Baiyun Sag and lower slope, respectively. The high heat flow in the slope is not only attributed to the intensely thinning of the lithosphere, but also upwelling of warmer mantle material beneath the slope during the lithospheric breakup, which could account for about 20 mW/m^2 of the observed heat flow. The thermal events due to magmatic injections have a significant effect on the thermal evolution of the eastern Qiongdongnan basin, and they still contribute about 10 - 25 mW/m^2 to the present surface heat flow. The analyses suggest that when studying tectono-thermai evolution of the deep-water basins in the South China Sea, it is necessary to consider these influential factors including sedimentation, seafloor spreading and magmatism.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2017年第3期56-64,共9页
Earth Science Frontiers
基金
国家自然科学基金项目(41176050
41576036
41376059)
关键词
构造热演化
数值模拟
白云凹陷
琼东南盆地
热流
tectono-thermal evolution
numerical modeling
Baiyun sag
Qiongdongnan Basin
heat flow
