鄂尔多斯盆地伊和乌素地区环河组砂岩地球化学特征及对物源区、构造背景的指示  

Geochemical characteristics of Huanhe formation sandstones in Yihewusu area of Ordos basin and the indications to provenance area and tectonic setting

作　　者：罗腾 张字龙[1] 贺锋[1] 张艳 LUO Teng;ZHANG Ziong;HE Feng;ZHANG Yan(CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]核工业北京地质研究院中核集团铀资源勘查与评价技术重点实验室,北京100029

出　　处：《世界核地质科学》2024年第2期261-274,共14页World Nuclear Geoscience

基　　金：中国铀业地勘项目(编号:202201-8);中核集团青年英才项目(编号:QNYC2301)和中核集团集中研发项目(编号:中核科发2021-143号)联合资助。

摘　　要：为了探讨下白垩统环河组砂岩的构造背景和物质来源,主要通过镜下鉴定和岩矿测试,分析了鄂尔多斯盆地伊和乌素地区环河组砂岩岩石学及地球化学特征。伊和乌素地区环河组砂岩主要成分为石英、长石和云母等矿物,含有少量黄铁矿和炭屑等暗色物质。颗粒磨圆呈次棱角状,分选较差,具有近源沉积的特征。砂岩元素地球化学分析具有SiO2含量较高(平均为71.69%),Al2O3含量中等(平均为12.39%),其他元素含量较低的特点。化学蚀变指数(CIA)平均为60.92,化学风化指数(CIW)平均为68.47,表明源区源岩经历了中等强度的风化作用。微量元素地球化学结果显示:研究区环河组砂岩富集Ba、Th、La和U等元素,亏损Nb、Zr、Ho和Er等元素。稀土元素配分图反映研究区环河组砂岩Eu显示负异常,轻稀土元素富集,重稀土元素亏损,LREE/HREE平均为10.23,La/Yb平均为16.27,LaN/YbN平均为11.65。伊和乌素地区环河组砂岩的母岩沉积构造背景为活动大陆边缘,主要物源区为长英质火成物源区。综合研究认为:伊和乌素地区环河组砂岩母岩物源区主要来自狼山和乌拉山地区。In order to explore the tectonic background and material sources of the sandstones of Lower Cretaceous Huanhe formation,the petrological and geochemical characteristics of the sandstones of Huanhe formation in Yihewusu area of Ordos basin were analyzed mainly through microscopic identification and petrographic and mineralogical tests.The main components of the sandstone of Huanhe formation in Yihewusu area are quartz,feldspar and mica,with small amounts of dark minerals such as pyrite and charcoal fragments.The grains are rounded and sub-angular,poorly sorted,and have the characteristics of near-source deposition.The elemental geochemical analysis on the sandstones are characterized by high SiO2 content(71.69%on average),medium Al2O3 content(12.39%on average)and low content of other elements.The average chemical alteration index(CIA)of the rocks and minerals is 60.92 and the average chemical weathering index(CIW)is 68.47,indicating that the source rocks of the provenance area have experienced moderate intensity weathering.The standardized spider-web diagram of trace element spheroidal meteorites shows that Huanhe formation in the study area enriched in elements such as Ba,Th,La and U,and deficient in elements such as Nb,Zr,Ho and Er.The Rare Earth Element(REE)pattern shows that the sandstones of Huanhe formation in the study area bears negative anomalies in Eu,with an average of 10.23 for LREE/HREE,16.27 for La/Yb,and 11.65 for LaN/YbN.The tectonic background of the sandstones deposition in Yihewusu area was the active continental margin,and the main source area is the felsic igneous rock.It is believed that the original provenance area of the sandstones of Huanhe formation in the Yihewusu area mainly come from the Wolf Mountain and Wulashan diserict.

关 键 词：砂岩地球化学 构造背景 物源分析 环河组 伊和乌素地区 

分 类 号：P619.14[天文地球—矿床学]