南海北部陆缘黏土矿物组合特征与地质意义

采用沉积矿物分析方法对南海北部九口探井渐新世—中新世沉积物进行系统的黏土矿物分析.结果表明:南海北部沉积物黏土矿物组成随时间及空间呈现规律性变化,黏土矿物伊/蒙转化深度具有自北向南逐步变浅的规律,与地温梯度升高变化趋势基本一致,这种黏土矿物伊/蒙转化的变化规律反映了南海北部洋陆过渡地壳减薄,莫霍面抬升,热流值升高的趋势.通过黏土矿物组合演变特征与热流变化趋势的相关关系,可以预测区域性温度场变化规律,加深对南海北部洋陆过渡地壳厚度变化的认识.

Characteristics of Clay Mineral Assemblage in Northern South China Sea Continental Margin and Its Geological Implications

The clay minerals of sediments from 9 wells in the northern South China Sea during the period from Oligocene to Miocene. were systemically analyzed based on sedimentary mineral analytical methods, Results show these clay minerals assemblage changes regulary with time and space. Illite smectite transition depth decreases from north to south, which is similar to the increasing trend of geothermal gradients. This illite smectite transition pattern reflects the thinning of the oceanic continental transitional crust in the northern South China Sea, and the uplifting of Moho surface, and the increasing of thermal flow index. The study of the relationship between clay mineral assemblage evolution and the trend of thermal flow change can help to forecast regional temperature field change law and understand thickness change of the oceanic continental transitional crust in the northern South China Sea.