延长探区南部盒8段稀土元素地球化学示踪

Geochemical Tracing of Rare Earth Elements of He 8 Member In Southern Yanchang Exploration Area

延长探区南部盒8段具有较大的天然气勘探开发潜力。通过分析延长探区南部盒8段泥岩样品中稀土元素地球化学特征,探讨了延长探区盒8段沉积环境及成岩物质来源。结果表明,研究区盒8段泥岩轻重稀土元素比值较大,分异程度较高,属于轻稀土中度富集型,δ(Ce)和Ceanom指示泥岩沉积时期水体整体处于缺氧的还原环境中,稀土元素特征和La/Yb-ΣREE判别图解指示延长探区南部盒8段构造环境稳定,存在多源分区性,源岩物质来自上地壳,源岩主要为花岗岩、沉积岩与钙质泥岩混合区,物源区主要为南部的祁连—秦岭古陆造山带的沉积岩母岩区和源自大陆边缘抬升基底型的花岗岩母岩区。

He 8 member in southern Yanchang exploration area has great potential for natural gas exploration and development.Based on the analysis of REE geochemical characteristics of mudstone samples from He 8 member in southern Yanchang exploration area,the sedimentary environment and diagenetic material source of He 8 member in Yanchang exploration area are discussed.The results show that the ratio of light rare earth elements to light rare earth elements in the mudstone of He 8 member in the study area is large,and the degree of differentiation is high,which belongs to the light rare earth medium enrichment type,δ(Ce)and Ceanom indicate that the whole water body was in anoxic reduction environment during mudstone deposition,Characteristics of rare earth elements and La/Yb-ΣREE discrimination diagram indicates that the structural environment of He 8 member in southern Yanchang exploration area is stable,and there is multi-source zoning.The source rocks are mainly composed of granite,sedimentary rock and calcareous mudstone.The provenance areas are mainly the parent rock area of sedimentary rocks in southern Qilian-Qinling ancient continental orogenic belt and the parent rock area of granites derived from the uplift basement type of continental margin.