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细粒泥岩记录并反映着源区及沉积区的重要地质信息.塘沽地区沙河街组下部发育一套湖相含云质泥岩,为了解该地区的构造背景、沉积背景、风化程度以及物源属性,对25块含云质泥岩的地球化学特征进行了全面的分析.经“去白云石”调整后,各类元素地球地化参数及图解反映出了一致的地质信息.其中,高∑REE值(154.0×10-6~219.3×10-6)、中等强度的负铕异常(0.64~0.73)以及包括K2O/Na2O-SiO2,SiO2/Al2O3-K2O/Na2O和判别函数几类双变量图解均指示塘沽地区具有主动大陆边缘(安第斯型)的构造背景;SiO2-(K2O+Na2O+Al2O3)图解指示岩石沉积期气候干旱,相当B(200.17~313.21)指示沉积水体为咸水类型,近似黄铁矿矿化度(approximate degree of pyritization,简称DOPapx)(0.02~0.38)、自生铀(0.14~1.22)及U/Th(0.17~0.44)指示水体具备常氧属性;化学蚀变指数(chemical index of alteration,简称CIA)(51.26~65.74),长石蚀变指数(plagioclase index of alteration,简称PIA)(51.65~78.06),修正成分变异指数(modified index of composition variation,简称ICVm)(0.67~1.24)及A-CN-K图解反映了母岩经受了弱-中等强度的风化程度;判别函数图解、K-Rb双变量判别图解、A-CN-K图解、Al2O3/TiO2指标(23.37~28.58)、与上地壳(upper continental crust,简称UCC)相似的稀土配分模式及负铕异常则共同确定长英质岩石为含云质泥岩的母岩来源.在上述背景条件的约束下,研究表明塘沽地区沙河街组含云质泥岩的物质来源应主要由燕山褶皱带提供.
The fine-grained mudstone records and reflects the important geological information of the source area and the sedimentary area.Development of a set of lacustrine-rich mudstone in the lower part of Shahejie Formation in Tanggu area is of great significance in understanding the tectonic setting, sedimentary background, weathering degree, , The geochemical characteristics of 25 mudstone with cloud are analyzed comprehensively.Geochemical parameters of all kinds of elements and their maps reflect the same geologic information after adjustment to “go dolomite” REE (154.0 × 10-6 ~ 219.3 × 10-6), moderate negative Eu (0.64-0.73), and bivariate diagrams including K2O / Na2O-SiO2, SiO2 / Al2O3-K2O / Na2O and discriminant functions Both indicate the tectonic setting of the active continental margin (Andean type) in the Tanggu area. The diagram of SiO2- (K2O + Na2O + Al2O3) indicates the arid climate during the depositional period of the rocks, and the equivalent B (200.17 ~ 313.21) indicates that the sedimentary body is of saltwater type, The approximate degree of pyritization (DOPapx) (0.02-0.38), authigenic uranium (0.14-1.22) and U / Th (0.17-0.44) indicate that the water body possesses normoxic properties. The chemical index of alteration (CIA) (51.26 ~ 65.74), feldspar alteration index (plagiocl ase index of alteration (referred to as PIA) (51.65 ~ 78.06), modified index of composition variation (ICVm) (0.67 ~ 1.24) and A-CN- , K-Rb bivariate discriminant diagram, A-CN-K diagram, Al2O3 / TiO2 index (23.37-28.58), similar to the upper continental crust (UCC) Negative Eu anomaly together determine the source rocks of felsic rocks as the source rocks of the dolomitic mudstones.Under the above background conditions, the study shows that the source of the Shahejie Formation cloud-bearing mudstones in Tanggu area should be mainly provided by the Yanshan fold belt.