元素地球化学与黏土矿物特征是反映古环境变化的敏感指标,其在一定时间内含量的变化能够较好地对环境进行指示。以渤海湾盆地周缘大奎山地区为例,结合野外观察,应用黏土矿物和地球化学特征分析下石盒子组的古环境。结果表明:剖面岩性组合、矿物微观特征显示为曲流河三角洲相沉积;剖面化学风化作用强,CIA平均值为84.67,Mg/Ca平均值为0.52;大量伊-蒙混层矿物出现,平均值为58.6%,高岭石矿物含量远高于伊利石、绿泥石矿物,早期可达51%,指示为温暖湿润气候下的沉积;微量元素和稀土元素显示下石盒子组物源来自于大陆上地壳;Sr/Ba、V/Zr、m平均值分别为0.33、0.36、3.70,显示海陆过渡相沉积;Ni/Co、U/Th、V/Cr平均值分别为2.43、0.38、1.06,显示沉积于氧化环境。

Element geochemistry and clay mineral characteristics are sensitive indicators reflecting changes in the ancient environment, and their changes in content over a certain period of time can effectively indicate the environment. Taking the Dakui Mountain area of the Bohai Bay Basin as examples, We analyzed the paleoenvironment of the Lower Shihezi Formation through clay mineralogy and geochemical methods.Results indicate that the lithological assemblage and mineral microscopic characteristics of the profile show that they are meandering river delta facies deposits. The profile has strong chemical weathering, with an average CIA value of 84.67 and an average Mg/Ca value of 0.52; A large amount of illite montmorillonite mixed layer minerals appear, with an average value of 58.6%. kaolinite content reaches up to 51% in the early stage, suggesting deposition under a warm and humid climate. Trace elements and rare earth elements indicate that the source of the Lower Shihezi Formation comes from the continental upper crust.Parameters such as Sr/Ba (avg. 0.33) and V/Zr (avg.0.36) indicate transitional facies between land and sea; The average values of Ni/Co, U/Th, and V/Cr are 2.43, 0.38, and 1.06, respectively, indicating deposition in an oxidizing environment.

               
                    0引言
1区域地质背景
2样品采集及测试方法
2.1露头样品采集
2.2测试方法
3岩石学与地球化学特征
3.1岩石学特征
3.2主量元素特征
3.3微量元素与稀土元素特征
4古环境讨论
4.1古地理环境
4.1.1水动力环境
4.1.2水体盐度
4.1.3水体氧化还原
4.2古气候判别
4.2.1采用黏土矿物特征判定古气候
4.2.2采用CIA值特征判定古气候
4.2.3采用Mg/Ca值特征判定古气候
5结论