摘要
准噶尔盆地南缘硫磺沟地区伴随铀矿化发育较多地沥青、油气残留物。为查明两者间的关联性,对含地沥青铀矿化砂岩进行了流体包裹体测试和有机地球化学分析。镜下观察发现,包裹体以含烃盐水包裹体和液烃包裹体为主,少量气烃包裹体。测温结果表明,含烃盐水包裹体均一温度及盐度整体中等偏低,分别集中于60~90℃、0%~8%NaCl。结合GOI统计及酸解烃测试结果得出含矿砂体主要存在一期中等偏弱的油气充注。气相色谱-质谱分析得出：主峰碳为C_（14）~C_（25）,单峰型;OEP与CPI分别为0.474~1.58、0.887~2.70,分布较分散;Pr/Ph为0.40~1.43,多小于1;Pr/nC_（17）、Ph/nC_（18）分别为0.164~0.833、0.595~1.54,质量色谱图基线＂鼓包＂不明显。以上表明油气有机质来源以低等藻类为主,总体处于较强还原环境,成熟度差异较大,生物降解微弱。基于油气还原与铀成矿间的关系及野外地质特征,认为油气还原对本区铀成矿有两大作用：一是对下中侏罗纪的早期铀矿体起保矿及隐蔽作用;二是进一步提高上侏罗统砂岩层的还原容量,为后期铀成矿提供所必需的还原场。
The Liuhuanggou area in the southern margin of the Junggar Basin developed many residues of oil gas-asphalt in company with uranium mineralization.In order to find out their spatial and temporal distribution and genetic relationship,fluid inclusion and organic geochemistry of asphalt sandstone ore bodies have been investigated.Microscope observation found that fluid inclusions in the ore-hosting sandstone are composed dominantly of liquid hydrocarbon inclusions and hydrocarbon-bearing brine inclusions,with minor gas hydrocarbon inclusions.The homogenization temperature and salinity of the hydrocarbon fluid inclusion are 60℃ to 90℃ and 0%to 8%NaCl respectively,indicating a kind of mediumlow temperature and salinity fluid inclusion.GOI statistics and acidolysis hydrocarbon experiment results demonstrate that ore-bearing sandstone has experienced one medium to weak rapid hydrocarbon-charging.Gas chromatography-mass spectrometry analysis shows that the peak carbon number of n-alkanes in organic matter is C_（14）~C_（25）,with the single peak type,suggesting that the main source of organic matter is algae.Odd-even predominance index（OEP） and carbon preference index（CPI） are 0.474~1.58 and 0.887~ 2.7 respectively,displaying that the organic matter has different maturity.The ratio of pristine to phytane（Pr/Ph） varies from 0.40 to 1.43,with most under 1,indicating a deoxidization environment for the organic matter.Pr/nC_（17） and Ph/nC_（18） is 0.164 ~ 0.833 and 0.595 ~ 1.54 respectively,and the bulge shape of convex baseline in the total ion current figure is not obvious.The features mentioned above indicate that oil and gas underwent weak microbial degradation.On the basis of the relationship between the reduction of hydrocarbon and uranium mineralization,along with field geological characteristics,we suggest that oil and gas reduction in the area has two functions to the uranium mineralization：the first is to protect and hide the early uranium deposit and the second is to further improve the reduction ability of the sandstone layers,thus providing the reducing agent for late uranium mineralization.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2016年第3期475-488,共14页
Acta Geologica Sinica
基金
部级核能开发科研项目"准噶尔大型叠合盆地地浸砂岩型铀矿预测技术研究"
国家自然科学基金项目(编号41072069)联合资助成果
关键词
硫磺沟地区
铀矿化
油气还原
流体包裹体
有机地球化学
Liuhuanggou area
uranium mineralization
reduction of oil ＆ gas
fluid inclusion
organic geochemistry
