鄂尔多斯盆地西南部下白垩统赋矿砂岩成矿流体特征及其地质意义  

Characteristics and geological implications of ore-forming fluids of the Lower Cretaceous U-bearing sandstones in the southwestern Ordos basin

作　　者：王婷婷 邱林飞 贺锋[1,2,3] 武正乾 刘坤鹏[4] 张良 韩美芝 WANG Tingting;QIU Linfei;HE Feng;WU Zhengqian;LIU Kunpeng;ZHANG Liang;HAN Meizhi(National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing,Beijing 100029,China;Beijing Research Institute of Uranium Geology,Beijing 100029,China;CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing 100029,China;Research Institute No.203,CNNC,Xi’an 710008,China)

机构地区：[1]铀资源探采与核遥感全国重点实验室,北京100029 [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 [4]核工业二〇三研究所,陕西西安710008

出　　处：《世界核地质科学》2024年第6期1089-1105,共17页World Nuclear Geoscience

基　　金：国家自然科学基金(编号:42302180);中核集团青年英才项目(编号:地QNYC2402);中核集团集中研发项目(编号:中核科发2021-143号)资助。

摘　　要：砂岩型铀矿是全球目前最主要的开采铀矿床类型,近年鄂尔多斯盆地西南部下白垩统砂岩型铀矿获得重要找矿线索,在镇原新庄、彭阳等地区的下白垩统环河组和洛河组均发现新的铀矿化,但目前其成矿流体演化、成矿作用过程尚不清晰。为了确定赋矿砂岩的成矿流体特征以及演化过程,探讨成矿流体对铀成矿过程的影响,对镇原地区铀矿化层及其上下的典型样品展开岩相学、流体包裹体和地球化学等方面的研究。研究表明:赋矿砂岩经历复杂的成岩作用过程,包括褐铁矿化、赤铁矿化、早期碳酸盐化、绿泥石化和硫化物化(黄铁矿、闪锌矿和黄铜矿)等,其中硫化物化以及与之相关的碳酸盐、重晶石充填与铀成矿密切相关;成矿流体盐度较低,温度集中130~180℃之间,高于白垩系大埋深时的温度,可能是受到早白垩世区域热事件或者深部来源流体的影响;成矿流体富含有机质和U、Fe、Mo、Re、Cu和Zn等成矿元素,很可能均来自于“延长组第7”段烃源岩,符合“渗出”型铀成矿作用特点。Sandstone-type uranium deposit is currently the most significant mining type of uranium deposit in the world.In recent years,significant breakthroughs have been made in the exploration of sandstone-type uranium deposits in the Lower Cretaceous of the southwestern Ordos basin.New uranium mineralization has been discovered in the Lower Cretaceous Huanhe and Luohe formations in areas such as Zhenyuan,Xinzhuang and Pengyang.However,the evolution of ore-forming fluids and the metallogenic process are still unclear.To determine the characteristics and the evolution process of ore-forming fluids in the U-bearing sandstones,as well as to investigate their impact on the uranium mineralization process,studies were conducted in petrography,fluid inclusions,and geochemistry of typical samples from key regions.The research indicated that the U-bearing sandstones had undergone complex diagenetic processes,including limonitization,hematitization,early carbonatization,chloritization,sulfuration,and so on.Among these,sulfuration and the associated carbonate and barite filling were closely related to uranium mineralization.The ore-forming fluids were low in salinity and temperatures ranging from 130 to 180°C,which was higher than the maximum burial temperature of the Cretaceous strata.This may be due to the influence of early Cretaceous thermal events or fluids from deep sources.The ore-forming fluids were rich in organic matter and ore-forming elements such as U,Fe,Mo,Re,Cu and Zn,likely originating from the“Chang 7”hydrocarbon source rocks,consistent with the characteristics of“exhalative”uranium mineralization.

关 键 词：成矿流体 成矿过程 下白垩统 砂岩型铀矿 鄂尔多斯盆地 

分 类 号：P619.14[天文地球—矿床学] P59[天文地球—地质学]