新疆巴什布拉克地区有机地球化学特征及其对铀成矿的控制  

The organic geochemical characteristics and its controls on uranium mineralization in the Bashibulake area,Xinjiang

作　　者：刘章月[1] 秦明宽[1] 蔡根庆[1] 刘红旭[1] 耿英英[1] 

机构地区：[1]核工业北京地质研究院中核集团铀资源勘查与评价技术重点实验室,北京100029

出　　处：《地学前缘》2015年第4期212-222,共11页Earth Science Frontiers

基　　金：国家科技支撑计划项目(2011BAB06B00);国家高技术研究发展计划"863"项目(2012AA061801);国家重点基础研究发展计划"973"项目(2015CB453004)

摘　　要：巴什布拉克铀矿床是新疆典型的与地沥青有关的砂岩型铀矿床。研究该矿床油气有机质来源、演化程度及后期降解过程,有助于深入解读原生红层在油气二次还原条件下的铀富集机理。本文针对该区铀矿化与油气密切相关的特点,采集了钻孔中具明显油浸的铀矿化砂岩和砾岩进行提取物分析。通过对提取物氯仿沥青“A”及其族组成和饱和烃气相色谱分析可见,有机质正构烷烃主峰碳为C17、C18、C20、C24和C25;（C21＋C22）/（C28＋C29）为0.58-12.17;Pr/Ph为0.40-1.47;Ts/Tm为1.3-16.1,高含量的系列重排藿烷化合物和“V”型甾烷分布,显示该区油气有机质主要来源于中下侏罗统湖相沉积。OEP为1.04-1.14,深部样品的OEP〈1.0;C-21/C＋22为0.18-2.11,指示局部烃源岩可能受到热改造提前进入生油门限,导致矿区深部浸入的油气有机质演化程度较高。早期浸入的油气有机质饱和烃气相色谱基线呈上飘“鼓包”状突出,Pr/nC17为0.6-0.9,Ph/nC18为0.8-11.98,表明受到氧化和微生物降解作用,在此过程中铀发生沉淀和富集。铀矿化主要受油气氧化和降解产物地沥青分布范围控制。Bashibulake uranium deposit is a typical sandstone-type uranium deposit associated with landbitumen in Xinjiang. Researching the oil and gas organic matter sources, evolution degree and late degradation process have great help for the further understanding of uranium enrichment mechanism of primary red beds in oil and gas second reduction. Aiming at the characteristics that uranium mineralization is closely related to oil and gas, we collected uranium mineralized sandstone and conglomerate that with obvious oil immersion characteristic in the drilling and then analyzed its extraction. The extract analysis of chloroform bitumen ＂A＂ and its group composition and saturated hydrocarbon gas chromatography shows that the peak carbon number of n-alkanes in organic matter belonged to C17, C18, C20, C24 and C2s ; （C21 ＋C22）/（C28 ＋ C29）is 0. 58 - 12.17; Pr/Ph is 0.40 - 1.47; Ts/Tm is 1.3 - 16. 1. High content serial rearrangement happens and distribution of V-type sterane revealed that the oil and gas organic matter was mainly from the middle and lower Jurassic lacustrine deposits. OEP is 1.04- 1. 14; OEP of deep samples are 〈1.0;C21^-/C22^＋ is 0. 18 - 2. 11, which indicates that local hydrocarbon source rocks may have undergone thermal modification, entered oil generation threshold earlier and resulted in higher organic matter evolution degree of immersed oil and gas in deep mining area. The gas saturated hydrocarbon gas chromatography of earlier immersed oil and gas organic matter show a bulge shape convex baseline, and Pr/nCl7 is 0. 6 - 0. 9 and Ph/nC18 is 0. 8 - 11.98, which indicate that oil and gas have undergone oxidation and microbial degradation, and uranium was precipitated and enriched during this process. Uranium mineralization was mainly controlled by the distribution of land-bitumen which is the product of oil and gas oxidation and degradation.

关 键 词：巴什布拉克铀矿床 二次还原 有机地球化学 微生物降解 铀沉淀和富集 

分 类 号：P619.14[天文地球—矿床学]