鄂尔多斯镇原地区下白垩统砂岩地球化学特征及其对物源区、构造背景的指示  

Geochemical characteristics of Lower Cretaceous in Zhenyuan area of Ordos Basin and its indication to provenance and tectonic setting

作　　者：何中波 胡宝群[1] 冀华丽[2,3] 贺锋 耿英英[2,3] 黄少华 朱满怀[1] HE Zhongbo;HU Baoqun;JI Huali;HE Feng;GENG Yingying;HUANG Shaohua;ZHU Manhuai(State Key Laboratory Breeding Base of NuclearResources and Environment,East China University of Technology,Nanchang,330013;Beijing Research Institute of Uranium Geology,Beijing,100029;CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Techniques,Beijing,100029)

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]核工业北京地质研究院,北京100029 [3]中核集团铀资源勘查与评价技术重点实验室,北京100029

出　　处：《地质论评》2024年第4期1291-1313,共23页Geological Review

摘　　要：笔者等通过对鄂尔多斯盆地镇原地区下白垩统砂岩进行主量元素、微量元素及稀土元素REE等地球化学分析,就下白垩统砂岩的沉积再循坏特征、化学风化及其构造背景和物质来源等展开讨论。研究表明:(1)下白垩统洛河组、环河组和罗汉洞组的物源主体上具有相似性,且在构造背景、物源区及物源特征上有良好的继承性。物源区总体具有富石英、富方解石胶结物、钾长石或富钾矿物较斜长石多的特点,罗汉洞组较环河组和洛河组硅质更高、方解石胶结物更少、质更纯。稀土元素REE配分模式曲线一致,轻重稀土分馏明显,富集大离子亲石元素Ba、Pb、Sr和轻稀土元素,亏损高场强元素Nb、Ta、Th、Y等,自下而上随着地层变新,沉积岩中总的稀土含量有变小的趋势,重稀土元素分馏程度减小;(2)研究区下白垩统砂岩原始物质主要为长英质与基性岩混合岩(如中酸性侵入岩、长英质变质岩)及部分沉积岩。研究区大部分沉积物是鄂尔多斯盆地西南缘逆冲推覆带母岩风化剥蚀的产物搬运至此沉积形成,系首次沉积的物质,少数沉积物(即风成砂)为就地再次搬运堆积形成,系再循环沉积物质;(3)在构造背景上具有以被动大陆边缘构造环境占主要优势的特点。碎屑物主要来源于陆块源区,其次来源于再旋回造山带和混合源区。Objectives:Analyzed the geochemical analysis data of major elements,trace elements,and rare earth elements(REE)of the Lower Cretaceous sandstone,we studied its sedimentary cycle characteristics,chemical weathering,structural background,and material sources of the sandstone.Methods:Based on the geochemical analysis of major elements,trace elements and rare earth elements(REE)of the Lower Cretaceous sandstone in Zhenyuan area of Ordos Basin,this paper discusses the sedimentary recycling characteristics,chemical weathering,tectonic background and material source of the Lower Cretaceous red variegated sandstone.Results:①The Lower Cretaceous Luohe Formation,Huanhe Formation and Luohandong Formation are similar in provenance main body,and have good inheritance in structural background,provenance area and provenance characteristics.The REE distribution pattern curves of rare earth elements are consistent,with clear fractionation of light and heavy rare earth elements,enriched in large ion lithophile elements Ba,Pb,Sr,and light rare earth elements,and depleted in high field strength elements Nb,Ta,Th,Y,etc.From bottom to top,with the formation becoming newer,the total REE content in Sedimentary rock tends to decrease,and the fractionation degree of heavy REE decreases.②The original material of the Lower Cretaceous sandstone in the study area is mainly composed of felsic and mafic mixed rocks(such as intermediate-acid intrusive rocks,felsic metamorphic rocks)and some sedimentary rocks.③In the tectonic setting,the passive continental margin tectonic environment is the main advantage.The debris mainly comes from the continental source area,followed by the recycled orogenic belt and the mixed source area.Conclusions:The provenance area is generally characterized by rich quartz,rich Calcite cement,more potassium feldspar or potassium rich minerals than plagioclase.The Luohandong Formation is more siliceous than Huanhe Formation and Luohe Formation,with less Calcite cement and purer quality.Most of the sediments in the s

关 键 词：地球化学 物源属性 构造背景 下白垩统 鄂尔多斯盆地 

分 类 号：P619.14[天文地球—矿床学]