摘要
中晚三叠世鄂尔多斯盆地周缘各地块处于不同的构造演化阶段,盆内延长组沉积的物质来源一直是研究的热点和难点,尤其是盆地南缘的物源构成一直存在诸多争议。通过砂岩碎屑组分统计以及地球化学分析方法,结合研究区和周缘古陆的稀土元素特征,开展了鄂尔多斯盆地南缘长10-长8段的物源和源区构造背景研究,结果表明:研究层段具有中-近源的沉积特点,形成于弱氧化的浅水环境;长10-长8段的主体物质形成于岩浆岛弧背景,南缘西部地区的长8段存在再旋回造山带型物质;盆地南缘中东部的长10-长8段源区为阿拉善古陆和阴山古陆,西部地区长10-长9段碎屑物质主要来自于阿拉善古陆,在长8段则混入了祁连-秦岭地区的碎屑物质。这种多源区、多变化的物质组成与中三叠世盆地周缘造山活动密切相关,指示该区为源-汇体系研究的良好实例。这些认识有助于进行原盆沉积环境的恢复和有利储集砂体的预测,为研究区下一步油气勘探部署提供沉积理论依据。
During the Middle-Late Triassic,all tectonic blocks surrounding the Ordos Basin were in different stages of tectonic evolution.Especially in the southern margin of the basin,the detrital source is still controversial.Provenance of the Yanchang Formation in the basin is still under much debate,especially the Chang 10 to Chang 8 section.In this study,the sandstone detrital component and geochemical statistics in the bottom of Yanchang Formation(Chang 10-Chang 8)are analyzed to unravel their provenance.The results show that the Chang 10-Chang 8 section have the characteristics of shallow-water,intermediate-proximal source deposition with weak oxidation.The major materials of the Chang 10-Chang 8 section may have formed in an island arc.Moreover,there are recycled-orogenic materials in Chang 8 in the western part of the southern margin.The Chang 10-Chang 8 member was likely originated from the Alxa block and Yinshan paleo-continent in the southern part of the basin,the Chang 10-Chang 9 member may have originated mainly from the Alxa block in the western part of the southern margin,whilst the Chang 8 member was likely a mixture of clastic materials from the Qilian and Qinling regions.This multi-source and varying material composition may have closely related to the orogenic activities around the Middle Triassic basin,indicating that this area is an ideal target to revel the source to sink system.Our findings can assist the reconstruction of the basin depositional environment,and the prediction of favorable reservoir sandbodies,which provides the theoretical basis for future oil and gas exploration in the study area.
作者
李怡佳
阮壮
刘帅
常秋红
赖玮
杨志辉
LI Yijia;RUAN Zhuang;LIU Shuai;CHANG Qiuhong;LAI Wei;YANG Zhihui(School of Earth Sciences and Resources,China University of Geosciences,Beijing100083,China)
出处
《现代地质》
CAS
CSCD
北大核心
2020年第4期784-799,811,共17页
Geoscience
基金
中央高校基本科研业务费项目(2652017458)。
