二连盆地与地沥青密切相关的砂岩型铀矿床微观矿物特征及成因分析  

Features and the Origin of Mineral in Sandstone Type Uranium Deposit Related to Petroleum Asphalt in Erlian Basin of Inner Mogolia

作　　者：王文广[1] 

机构地区：[1]核工业北京地质研究院,北京100029

出　　处：《铀矿地质》2016年第5期270-278,共9页Uranium Geology

摘　　要：内蒙古二连盆地产在下白垩统碎屑岩系中的砂岩型铀矿床,其矿化与地沥青密切相关,有铀矿物存在之处必有地沥青;岩石中也普遍含地沥青。笔者通过蚀刻α径迹示踪,对铀含量在(200~1770)×10^(-6)的碎屑岩进行扫描电镜分析,采用分子量计算方法确定了该地区含铀碎屑岩中的铀是以多种超显微铀矿物形式存在。其中,以赛汉高毕铀矿床为代表,铀主要形成复成分磷钙铀矿。其它铀矿床也普遍有复成分磷钙铀矿产出:巴彦乌拉矿床样品因钙含量低、硅含量高,则铀石多于复成分磷钙铀矿;道尔苏矿床以铀石和磷铀矿为主,有少量沥青铀矿及复成分磷钙铀矿;哈达图矿床主要是沥青铀矿,未见复成分磷钙铀矿。除了地沥青之外,各矿床中与铀矿物共生的主要矿物还有草莓状、鲕粒状黄铁矿。由此推断,铀矿床的可能成因是:来自盆地深部的UH_3、PH_3、CaH_2、SiH_4、FeH_2、H_2S等在伴随油气向上运移过程中,由于温度、压力降低和氧化作用而发生分解及凝聚,形成草莓状、鲕粒状黄铁矿;同时派生出含U、P、Si、Ca等的氧化物的低温热水溶液,并最终结晶析出铀矿物,形成有大量黄铁矿共生的铀矿体;而油气经过长期挥发,最终演变成地沥青,成为铀矿物的载体。Sandstone type uranium deposits in the lower Cretaceous elastic rock of Erlian basin, Inner Mogolia are closely related to petroleum asphalt. In the basin, petroleum asphalt are common in rocks, and wherever there is uranium mineral, there must be asphalt. By the way of etched alpha particle tracking, SEM micro analysis was performed on elastic rocks with U content of （200-1770）×10^-6 and molecular weight calculation was used to identify the form of uranium and it was found that uranium is present in the form of ultramicro micrite in the U-bearing elastic rocks of the region. In Saihangaobi de posit, uranium is mainly in the form of tristramite, and tristramite are also found in other deposit more or less. Samples from the Bayanwula deposit contain less Ca but more Si, coffinite than tristramite. In Daoersu deposit uranium is mainly in coffinite and phosphuranylite, some in pitchblende and tristramite. In Hadatu deposit, uranium is mostly in pitchblende and no tristramite visible. Beside the asphalt, framboidal and oolitic as well as varied pyrite are also coexists with uranium in all the deposit, the origin of uranium mineralization possible are as fellow： uranium migrate and intrude together with petroleum - gas in the form of UH3, PH3, Call2, Sill4 , Fell2 and H2S from the deep, and framboidal and oolitic pyrites was formed by oxidation and condensation and hypothermal water solution of U, P, Si and Ca is derived to separate uranium by crystallization, and then asphalt is obtained by the long term volatilization of the hydrocarbon series in petroleum and becomes the carrier of uranium ore.

关 键 词：下白垩统碎屑岩系 砂岩型铀矿床 草莓状黄铁矿 铀矿物 U、 P、 Ca的氢化物 

分 类 号：P611[天文地球—矿床学]