东胜铀矿流体包裹体同位素组成与成矿流体来源研究  

Isotope Composition of Fluid Inclusion and Tracing to the Source of Mineralization Fluid in Dongsheng Uranium Deposit, North Ordos Basin

作　　者：李荣西[1] 赫英[2] 李金保[1] 李继宏[1] 李鑫[1] 

机构地区：[1]长安大学,西安710054 [2]西北大学,西安710069

出　　处：《地质学报》2006年第5期753-760,共8页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划"973"项目(编号2003CB2146000)资助的成果。

摘　　要：东胜铀矿与典型的层间氧化带砂岩型铀矿床特征明显不同。矿物流体包裹体分析表明东胜铀矿成矿流体温度主要为150～160℃。流体包裹体的3He/4He值为0.02～1.00R/Ra,是地壳比值的5～40倍,其40Ar/36Ar同位素比值高达584～1243,明显偏离大气氩的同位素组成(40Ar/36Ar=295.5)。流体包裹体的δ18OH2O在-3.0‰～-8.75‰之间,δD在-55.8‰～-71.3‰之间,具有大气降水与岩浆水混合流体的特点。铀矿底板高岭石δ18OH2O为6.1‰,δD为-77‰,具有岩浆水的特点。铀矿方解石脉的δ13CV-PDB为-8.0‰,δ18OH2O为5.76‰,显示出地幔来源的特征。东胜铀矿成矿流体He-Ar同位素和碳、氢和氧同位素组成特征一致表明,成矿流体具有地壳与深部混合流体的特征。结合区域地质分析认为,侏罗—白垩纪鄂尔多斯盆地北部隆起区大面积分布的富铀变质岩和花岗岩遭受风化剥蚀,被大气降水搬运到当时地貌较低的东胜地区沉积。中生代鄂尔多斯盆地构造热事件和岩浆活动,促使地下深部流体和浅部油气沿断裂带和活化的裂隙上涌,充注到含铀碎屑砂岩中,为铀的活化和成矿作用提供了重要的能量。Geochemistry characteristics of Dongsheng uranium ore are much different from that of standard interlayered oxidation type of sandstone uranium ore deposit. Mineral fluid inclusion of uranium sandstone analysis shows that the uranium ore formation temperature is 150～160℃. The ratio of 3He/4He is 0.02～1.00 R/Ra,which is about 5 to 40 times of the ratio of the crust. The ratio of 40Ar/36Ar is 584 to 1243, which is much higher than the value of the atmosphere. Theδ18OH2o and δD of fluid inclusion of uranium sandstone are -3.0‰-8. 75‰ and -55.8‰-71.3‰respectively, which shows some characteristics of mixture fluid of meteoric water with magma water. Theδ18OH2o and δD of kaolinite layer under uranium ore bed are 6.1‰ and - 77‰, which indicates characters of magma water. The δ13Cv -PDB and δ18OH2o of calcite vein in uranium ore are -8.0‰ and 5.76‰, which shows characters of mantal source. Results of isotope of mineral fluid inclusion indicate that uranium ore-formation fluid was a kind of mixture fluid of meteoric water with fluid soured from deep place under the crust. It is proposed that the metamorphic rock and granite with higher content of uranium distributed in northern uplift area of Ordos basin were denudated and transported to deposit in Dongsheng district. Tectonic and magmatic actives induced the fluid in deep place under the crust erupted through lived faults into deposits with higher content of uranium, which supplied the energy for formation of uranium ore.

关 键 词：HE-AR同位素 氢 氧同位素 流体包裹体 东胜铀矿 

分 类 号：P619.14[天文地球—矿床学]