摘要
为了解准噶尔盆地南缘硫磺沟地区中侏罗统头屯河组砂岩成岩—流体演化与铀成矿响应,进而客观评价其成矿潜力。通过光薄片鉴定、X衍射、扫描电镜分析得出:目的层主要为岩屑细砂岩,依次经历了浅埋藏、深埋藏和表生—热液成岩阶段,遭受较强的机械压实、胶结及溶蚀作用。其黏土矿物以高岭石为主,碳酸盐矿物有细亮晶和泥晶两类,硅质胶结微弱,局部见细晶黄铁矿及其褐铁矿氧化产物。成岩环境可能经历了由酸性到弱碱性再到酸性,由同生期氧化—浅埋期还原—短暂抬升期氧化还原过渡—缓慢沉降期还原增强—快速抬升期氧化的演化过程。砂岩中存在较多油气包裹体;酸解总烃为5.72~449.14μL/kg,以CH4为主;方解石脉δ13CV-PDB为-25‰^-6.7‰,δ18OV-SMOW为11.1‰~18.9‰;结合野外调查认为目的层存在一期中等偏弱的后生油气侵位,从而影响了砂体的Eh及p H值。以上成岩过程及烃类流体活动使得目的层早期形成了小型层间氧化带型铀矿并得以局部保存,晚期形成了一定规模的地表潜水氧化带型铀矿体。
To study the relationship between diagenesis-fluid evolution and uranium mineralization of J2 t sandstone in Liuhuanggou area,the southern margin of Junggar basin,finally assessing the metallogenetic potentiality. By means of microscope,X-diffraction and scaning electron microscopy,the author conducted that the studied rock are mainly rock-fragment fine sandstone,which underwent shallow burial period,deep burial period and hypergene-thermal period diagenetic evolution,finally suffered from relatively strong compaction,cementation and dissolution. The clay minerals are mainly kaolinite. There are also some fine sparry and micrite carbonate minerals,a few of siliceous cementations,fine grain pyrite and limonite locally. The diagenetic environment may experienced acid- weak alkalicy- acid and syngenetic oxidation-reduction in the shallow burial period-0xidation / reduction in the transitory elevation period- reduction enhancing in the deep burial period- oxidation in the period of large scale lifting evolutionary process.Simultaneously,hydrocarbon charging on the sandstone were proved by the following evidence： field investigating,oil and gas inclusions verificating,total acidolysis hydrocarbon range from 5. 72 μL / kg to 449. 14 μL / kg,mainly for the methane,C-O stable isotope values of calcite are-25‰ ^-6. 7‰,11. 1‰ ~ 18. 9‰,respectively,which influenced the geochemical properties（ Eh and p H） of sandstone. The above diagenetic and hydrocarbon evolution controlled the migration,accumulation and localization of uranium,namely it formated and locatly conserved some small interlayer oxidation type uranium deposits in the early phase and formed some groundsurface phreatic oxidation type uranium deposits in the later preiod.
出处
《沉积学报》
CAS
CSCD
北大核心
2016年第2期250-259,共10页
Acta Sedimentologica Sinica
基金
核能开发科研项目(H1142)
国家自然科学基金项目(41502099)~~
关键词
准噶尔盆地南缘
头屯河组砂岩
成岩作用
烃类流体
砂岩型铀矿
southern margin of Junggar Basin
J2t sandstone
diagenesis
hydrocarbon
sandstone-type uranium deposit
