松辽盆地东南隆起区上白垩统嫩江组泥页岩段地球化学特征与物源分析

嫩江组泥岩的地球化学分析结果表明:泥岩中含有一定量的铁镁质组分和较多的稳定组分。微量元素和稀土元素分析结果显示,嫩江组含油页岩段沉积时期存在多个物源。CIA和PIA值没有随着埋深的减少而增加,说明嫩江组泥岩受后期风化影响很小。CIA值为70.5~77.0,Th/U值为2.67~3.98,说明泥岩源区经历了中等强度风化作用。Zr/Sc—Th/Sc图解表明泥岩的化学成分受源岩成分控制。通过源岩和构造背景判别图以及前人资料可知,松辽盆地嫩江组母岩主要为海西期花岗岩,源岩的构造背景为大陆边缘造山带火山岛弧岩系。物源中输入较多的铁镁及含钙物质,促进油页岩的形成。

Geochemical characteristics and implications for provenance of shale from Upper Cretaceous Nenjiang Formation of southeastern uplifted area in Songliao Basin

The geochemical analysis of the mudstone from Nenjiang Formation indicates that the mudstones contain a certain amount of femic materials and many stable components． The PAAS- standardized distribution curves of trace elements and ＲEEs suggest that the material of the oil shale member of the Nenjiang Formation came from several provenances． The CIA and the PIA not increase with the decreasing of depth，which indicates that the influence of later weathering on mudstone of the Nenjiang Formation is very small． The CIA ranges from 70. 5 to 77. 0 and the Th/U ratio ranges from 2. 67 to 3. 98， which suggest that provenances underwent weathering processes in moderate intensity． The Th /Sc and Zr/Sc ratios illustrate that these mudstones were mainly controlled by the components of source rocks． On the basis of source rocks，discrimination diagrams of tectonic setting and previous research data，we conclude that the provenances of the oil shale member of Nenjiang Formation in Songliao Basin were mainly Hercynian granites． Tectonic setting of the source rocks were the continental margin orogenic belt and belonging to continental island arc volcanic series． More input of iron，magnesium and calcium materials to prove- nance promote the formation of oil shale．