柴西缘英东地区上油砂山组黄铁矿与砂岩型铀矿化关系研究  

Relationship Between Pyrite-and Sandstone-Type Uranium Mineralization in the Shangyoushashan Formation in the Yingdong Area,Western Qaidam Basin

作　　者：李强 赵兴齐[2] 陈擎 陈云杰 陈斌 荣骁 赵旭 康利刚 时志浩 李天石 龚奇福 LI Qiang;ZHAO Xingqi;CHEN Qing;CHEN Yunjie;CHEN Bin;RONG Xiao;ZHAO Xu;KANG Ligang;SHI Zhihao;LI Tianshi;GONG Qifu(No.203 Research Institute of Nuclear Industry,Xi’an 710086,Shaanxi,China;CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]核工业二〇三研究所,陕西西安710086 [2]中核集团铀资源勘查与评价技术重点实验室,核工业北京地质研究院,北京100029

出　　处：《大地构造与成矿学》2024年第6期1274-1285,共12页Geotectonica et Metallogenia

基　　金：中国核工业地质局项目(202219、202219-1);中国铀业有限公司-东华理工大学核资源与环境国家重点实验室联合创新基金项目(2022NRE-LH-17)联合资助。

摘　　要：英东地区砂岩型铀矿是近年在柴达木盆地西缘古-新近系中新发现的具有工业价值的砂岩型铀矿。为了查明赋矿地层中黄铁矿成因及形成机理,探讨其与铀矿化之间关系,本文对含矿砂岩中的黄铁矿、铀矿物开展矿物学研究,并分析了黄铁矿微量元素和S同位素组成。结果表明:①上油砂山组含矿砂岩中黄铁矿主要以胶状和粒状形式存在,多与铀矿物相伴生,稀土元素配分模式显示其具有相似的物质来源。黄铁矿显著富集As且Co/Ni值较低,表明其形成于低温沉积环境。②上油砂山组含矿砂岩中黄铁矿δ^(34)S_(CDT)分布范围为1.2‰~14.1‰,平均值为7.9‰,表明硫的分馏程度较低,岩石中硫的来源比较单一,认为黄铁矿的形成与有机物热解作用密切相关,其硫源主要为油气和沉积硫化物。③综合研究区铀成矿地质条件,认为英东地区上油砂山组含矿砂岩中黄铁矿为铀成矿提供了必要的还原剂,增加了目的层砂体还原容量,有利于砂岩型铀矿的形成。The newly discovered sandstone-type uranium deposit in the Yingdong area is situated in the Paleogene-Neogene sediments on the western margin of the Qaidam Basin.In an attempt to determine the genesis and formation mechanism of pyrite in the ore-bearing strata and explore its relationship with uranium mineralization,this study comprehensively investigated the mineralogical characteristics of pyrite and uranium-bearing minerals,trace elements and S isotopes of pyrite in the ore-bearing sandstone.The results show that:(1)Pyrite in the ore-bearing sandstones of the Shangyoushashan Formation was mainly preserved as colloidal and granular.The pyrite is mostly symbiotic with asphaltene uranium minerals and shares similar REE distribution characteristics,indicating similar metallogenic material sources.The low Co/Ni ratios and prominent as enrichment in the pyrite indicate a sedimentary origin and low-temperature environment.This implied that the ore-forming fluid was of low temperature.(2)The δ^(34)S_(CDT) values of pyrite from the ore-bearing sandstone of the Shangyoushashan Formation ranged from 1.2‰ to 14.1‰,with an average of 7.9‰.This range of variation is small,suggesting a low degree of sulfur fractionation and a homogenous source of sulfur.It is widely accepted that the formation of pyrite was associated with the pyrolysis of organic matters.(3)Based on the geological conditions of uranium mineralization in the study area,we propose that pyrite in the ore-bearing sandstone of the Shangyoushashan Formation in the Yingdong area offered a necessary reducing agent for the uranium mineralization,which increased the reduction capacity of the target layer sand body and served as a prerequisite for the formation of sandstone type uranium deposits.

关 键 词：黄铁矿 S同位素 砂岩型铀矿 上油砂山组 柴达木盆地 

分 类 号：P611[天文地球—矿床学]