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

松辽盆地青山口组一段主要为暗色泥岩,并发育多层品质较好的油页岩。对盆地东南隆起区NGN1井泥岩系统取样测试,地球化学分析结果显示:w(Si O2)为44.88%~57.75%,w(K2O)一般比w(Na2O)高,w(Mg O+Fe2OT3)为4.5%~10.01%,表明泥岩中含有较多的含钾矿物和一定的铁镁质成分。样品微量元素PAAS标准化配分曲线显示样品中元素富集、亏损均呈现基本一致的趋势,表明泥岩沉积时期存在一种主要物源。稀土元素球粒陨石标准化后呈现出明显的右倾趋势和Eu的负异常,显示物源来自上地壳。泥岩CIA指数为48~62,Th/U值大都集中在1.48~4,表明泥岩源区经历了低等的风化作用;Th/Sc--Zr/Sc图解显示泥岩中的沉积碎屑没有经历沉积再循环,受原岩成分控制,表明地球化学数据可以进行物源类型和构造环境判断。根据原岩和构造背景判别图解,松辽盆地东南隆起区青一段泥岩物源主要为中—晚侏罗世中酸性喷发岩,并混有海西期和燕山期花岗岩;原岩的构造背景为大陆边缘造山运动形成的大陆岛弧。

Geochemical characteristics and geological implications of mud shale from the 1st Member of Qingshankou Formation of southeastern uplifted area in Songliao Basin

The 1st Member of Qingshankou Formation in Songliao Basin is composed mainly of dark- colored mudstone，and developed in good quality oil shales． Based on systematic sampling，the geochemical analysis of the mudstone from Well NGN1 in the southeast uplift of Songliao Basin，was made by the authors． The results show the SiO2 content ranged from 44. 88% to 57. 75%，K2O generally higher than Na2O in content，and the parameterof (MgO + Fe2OT3 ) ranged from 4. 5% to 10. 01%，which indicates that the mudstone contained a relative quanti- ty of potassium- bearing mineral and a certain amount of femic constituents． The PAAS- standardized distributive curves of trace elements show the same enrichment and depletion trends among different samples，which suggests that the mudstone had a dominating provenance． The chondrite standard curve of rare earth elements reveals the enrichment in light ＲEE and negative anomalies of Eu，which shows the provenance of the mudstone came from the 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 suggest that the provenance had underwent a low weathering processes． The Th/Sc- Zr/Sc diagram shows that these mudstones were mainly controlled by source rocks，and their clastic deposits had not suffered sedimentary recycling，which means the provenance characteristics and tectonic setting of the mud- stones could be judged by the geochemical analysis． On the basis of sourse rocks and discrimination diagrams of tectonic setting，it was concluded that the provenances of the 1st Member of Qingshankou Formation were mainly intermediate- acid extrusive rocks from Mid- Late Jurassic，and also involved in Hercynian and Yanshanian grani- ties． The source rocks were formed in the continental margin orogenic belt and belonged to continental island arcvolcanic series．