尼日尔Termit盆地Yogou组泥岩地球化学特征及沉积背景

摘要

Yogou组泥岩是Termit盆地主要的烃源岩之一.为了揭示Termit盆地Yogou组沉积时期物源属性、物源区的构造背景及其沉积环境,通过对4口井20块泥岩样品的主量元素、微量元素和稀土元素测试,对Yogou组泥岩的元素地球化学特征进行了综合分析.结果显示:Yogou组上部以被动大陆边缘物源为主,下部以长英质物源为主,物源区处于大陆岛弧的构造背景条件下.Yogou组中-上部沉积时期水体盐度相对较低,为海陆过渡相沉积;Yogou组下部沉积时期水体盐度较高,为海相沉积.CIA指数、Sr/Cu值等指标表明,Yogou组沉积时期研究区处于湿热的气候条件;V/(V+ Ni)等指标说明,Yogou组沉积时期水体处于厌氧环境.%Yogou Formation mudstone is one of the main hydrocarbon source rocks in the Termit Basin.In order to reveal the sediment source provenance attribute,tectonic setting and sedimentary environment of the Yogou Formation,geoche mical elements of mudstones in the Yogou Formation were comprehensively analyzed,based on experimental data of the major elements,trace elements and rare earth elements of the 20 samples from 4 wells.The results show that the provenances of the upper Yogou Formation are derived from a passive margin source,while the provenances of the lower Yogou Formation are derived from a felsic source.The tectonic setting of the Yogou Formation provenance is similar to continental island arc.Water body during the deposition middle-upper Yogou Formation appears to have relatively lower salinity,in a marine-continental transition environment.The water body during the deposition of lower Yogou Formation appears to have relatively higher salinity,marine environment.According to CIA index and Sr/Cu ratio,the climate was warm-wet and water body was in the anaerobic environment based on the ratio of V/(V + Ni) during the Yogou Formation period.