松辽盆地东南隆起区青山口组一段泥页岩地球化学特征及地质意义

he lithology of the 1st member of Qingshankou Formation in Songliao Basin was dark-colored mudstone，and developed good quality oil shales. The geochemical analysis based on systematic sampling of the mudstone from Well NGN1 in the southeast uplift showed that the SiO2 content ranged from 44. 88% to 57.75%,，K2O content was generally higher than the Na2O content，and the parameter of（MgO+Fe2O3T）ranged from 4.5% to 10.01%，indicating that the mudstone contained a relative quantity of potassium-bearing mineral and a certain amount of femic constituents. The PAAS-standardized distribution curves of trace elements showed the same enrichment and depletion trends among different samples，which suggested the mudstone had a dominating provenance. The chondrite standard curve of rare earth elements revealed the enrichment in light REE and negative anomalies of Eu，this showed the provenance of the mudstone come from upper crust. The mudstone weathering and alteration index ranged from 48 to 62 and Th/U ratio mainly ranged from 1.48 to 4，both of which suggested that the provenance had underwent a low weathering processes. The Th/Sc-Zr/Sc diagram showed that these mudstones were mainly controlled by source rocks，and their clastic deposits had not suffered sedimentary recycling，which meaned we could judge the provenance characteristics and tectonic setting of the mudstones by the geochemical analysis. On basis of sourse rocks，discrimination diagrams of tectonic setting，we concluded that the provenances of the 1st member of Qingshankou Formation were mainly intermediate-acid extrusive rocks from Mid-Late Jurassic，and also involved Hercynian and Yanshanian granities. Source rocks were formed in the continental margin orogenic belt and belonged to continental island arcvolcanic series.