二连盆地赛汉高毕铀矿床渗出成矿作用和模式

Exudative Metallogeny and Model of Saihan Gaobi Sandstone-type Uranium Deposit in Erlian Basin

通过探讨二连盆地赛汉高毕铀矿成矿作用,构建铀成矿模式,总结成矿特征,提炼关键控矿要素,可指导矿床外围、深部和类似地区铀矿找矿。文章基于赛汉高毕铀矿床构造、建造、油气演化、铀矿化、铀成矿时代等分析,详细阐述了矿床矿石矿物、矿石元素地球化学特征。确认赛汉高毕铀矿床产于赛汉组上段建造间古河道中,受准宝力格深切断陷、贯通性断裂、赛汉晚期深切河道联合控制,形成透镜状或板状铀矿体,铀成矿作用与区域油气逸散活动、挤压构造活动密切相关;铀矿石中CaO+Al_(2)O_(3)和P_(2)O_(5)与铀含量呈正相关,Co、Ni、Zn含量高,Fe^(2+)/Fe^(3+)总体小于0.8;各类砂岩中酸解烃含量均比较高,Th/U均小于2,表明赛汉组上段原生环境主要为红杂色的氧化环境,灰色含矿砂体主要是渗出还原成因;矿石中铀是以多种铀矿物形式存在,主要有黄铁矿-铀矿物型、地沥青包裹铀矿物型和微粒碎屑铀矿物型。赛汉高毕铀矿床主要为渗出成矿作用,赋存于深部的富含有机质和四价铀的流体沿贯通断裂或高角度不整合和下切河道运移至上部赛汉组上段氧化砂体中,流体被分解形成黄铁矿、富含铁铝等杂质的磷钙铀矿、地沥青,粒径大的地沥青将已先结晶的黄铁矿和富含铁铝等杂质的磷钙铀矿包裹其中,大部分铀矿物就位于较小的地沥青的外侧和附近。

In order to explore the metallogeny and construct the metallogenetic model to provide guidance for uranium exploration in the periphery and depths of Saihan Gaobi uranium deposit in Erlian Basin,This paper summarized the oreforming characteristics,extracted the key ore-controlling factor by analyzing the tectonic activity,geological formation,evolution of oil and gas,uranium mineralization,and age of uranium mineralization in Saihan Gaobi uranium deposit.The study made a detailed description of the geochemical characteristics of ore minerals and elements present in the deposit.The Saihan Gaobi deposit was confirmed located at paleochannel between the upper member of Saihai Formation,controlled by the Zhunbaolige deep cut depression and the incised channels in late Saihan period.The uranium ore body are tabular or lenticular.The metallization was found closely related to regional oil and gas escape activity and the compressional tectonic activity.The uranium content in the ore is positive correlated with the content of CaO+Al_(2)O_(3) and P_(2)O_(5),while the overall content of Co,Ni,Zn,and Fe^(2+)/Fe^(3+)is relatively low,usually less than 0.8.Various types of sandstones exhibit a relatively high content of acid-dissolved hydrocarbons,and Th/U ratio is less than 2.These observations indicated that the primary environment of red mottled rock in the upper member of Saihan Formation was formed in oxidized environment and the gray ore-bearing sandstone body was mainly formed by exudative reduction.Uranium occurred in different uranium minerals,mostly co-existed with pyrite,coated with mineral pitch or micro debris uranium mineral.The mineralization in Saihan Gaobi uranium deposit was primarily attributed to exudative reduction,fluids rich in organic matter and tetravalent uranium,stored in the deep region,and transported to the oxidized sand bodies of the upper member of Saihan Formation through fractures or high-angle unconformities and undercutting channels.These fluids decomposed,resulting in the formation of pyrite,compound calcium phosphor uranium ore,and ground asphalt,which was previously crystallized in the ground asphalt.The majority of the uranium minerals are found on the outer side of the larger ground asphalt deposits,while most of the uranium minerals are situated near the smaller bitumen deposits.