鄂尔多斯盆地富县探区延长组长8、长6物源分析——来自岩石地球化学及重矿物的证据

鄂尔多斯富县探区中生界延长组近年来油气勘探一直未能获得大的突破，对物源方向认识有一定分歧。通过对该探区延长组砂岩研究认为：长8、长6砂岩类型单一，主要为长石砂岩和岩屑质长石砂岩，长石含量约20％-65％。其稀土元素总体中等一较高（88．94-225．1）×10^-6，轻稀土富集，基本不显示Eu和ce异常，球粒陨石标准化配分模式为右倾谱型。研究区不同分区重矿物组合具有差异性，其影响因素为不同的沉积分支体系分布。将延长组与周缘结晶基底进行对比，结合周缘古陆与重矿物分析，结果表明：北东物源为主要物源区方向，而吕梁山火成岩与延长组不具亲缘关系，秦岭造山带秦岭群和宽坪群不是研究区延长组主要物源区，北部阴山古陆乌拉山群麻粒岩一孔兹岩系为延长组主要母岩。

Provenance Analysis of Chang 8 and Chang 6 Members of Yanchang Formation in Fuxian Exploration Area of Ordos Basin --From Lithogeochemistry and Heavy Minerals Analysis

Abstract： Oil exploration in the southeast Ordos Basin in recent years made little progress due to ambiguous un- derstanding of the primary provenance of Yanchang Formation. The main types of clastic sandstones in Yan- chang Formation are arkose and lithic arkose distributed in Chang 8 and Chang 6 with 20% -65% feldspar. The REE patterns are characterized by medium to high REE contents （ 88.94 - 225.1 ） x 10 -6, enriched LREE, insignificant Eu and Ce abnormal. The REE patterns normalized by chondrite are fight-inclined. The diversity of heavy minerals assemblage represents different sedimentary system distribution. In comparison with crystalline basement, the analysis of old land and heavy ninerals assemblage, it suggests that Archean igneous rocks in Luliang Mountains have no genetic link to Yanchang Formation. The primary provenance of Yanchang Formation derived from granulite-khondalite series from Wulashan Group in Yinshan paleo-land in east-north, rather than from Qinling Group and Kuanping Group in northern Qinling Mountains.