我国最大古岩溶型铀矿床成因的同位素地球化学研究  

Isotopic Geochemistry of Metallogeny for the Largest Paleokarst Uranium Deposit in China

作　　者：闵茂中[1,2] 王湘云[1,2] 沈保培 文光斗[1,2] 樊涛 

机构地区：[1]南京大学地球科学系 [2]核工业中南地勘局303大队

出　　处：《沉积学报》1997年第1期118-122,共5页Acta Sedimentologica Sinica

基　　金：国家教委博士点基金;中国科学院矿床地球化学开放研究实验室基金

摘　　要：据对某大型古岩溶型铀矿床中铀－铅同位素体系及硫、碳、氧、氢同位素组成的研究结果，表明该矿床成矿物质源自矿区众多地层，成矿流体的变质水和古岩溶水（古大气降水）的混合水；成矿经历了古岩溶铀淋积富集，燕山早、晚期构造运动促使两次含铀热水溶液改造、叠加成矿（１３５～１１９．６５Ｍａ），成矿作用与古岩溶和区域地质构造演化密切相关。A uranium deposit is the largest paleokarst type U deposit in both scale and tonnage in China. The deposit is formed below a fossil cave and in a faulting solution breccia system in the Lower Carboniferous limestone. The temperature of mineralizing fluids ranges from 181℃ to 150℃. Four U Pb ages for pitchblende and whole rock ores, 135, 131, 119 and 65 Ma, have been determined, which are obviously younger than those of the wall rocks. Sulfur isotope data show that the δ 34 S values of pyrites from the ores range from 1.00‰ to -15.30‰ with a mean value of -6.87‰, closel to those of pyrites from the wall rocks(1.00‰～-15.60‰, mean-7.06‰), suggesting that the wall rocks are the source of sulfur for mineralization. The five analyzed samples of calcites from the ores have δ 13 C values between 0.34‰ and -3.19‰(mean-1.50‰). The similarity between the average carbon isotope composition of the ores(-1.50‰) and the wall rocks(0.53‰) is interpreted to result from an isotope exchange between the wall rock and mineralizing fluid. The lead isotope composition of pyrites from the ores and whole rock of Lower Carboniferous sugggests that the source of lead and uranium in the deposit is various in strata of the ore field. The values of δ 18 O and δD for mineralizing fluids range from 1.5‰ to 7.3‰ and from -30.4‰ to -84.9‰, respectively, indicating that the mineralizing fluid is a mixed water of metamorphic and meteoric waters. The mineralizing process is closely related to development history of regional tectonic movemnets and multi episode paleokarstification. Thus, it is named as hydrothermal reworked paleokarst type uranium deposit.

关 键 词：铀矿床 古岩溶 同位素地球化学 矿床成因 

分 类 号：P619.140.1[天文地球—矿床学] P619.140.4[天文地球—地质学]