【摘要】 赣杭铀成矿带是我国最大的火山岩型铀成矿带,大茶园（661）铀矿床是该成矿带东段最重要的火山岩型铀矿床,矿体赋存于晚中生代磨石山群九里坪组流纹岩中。为探讨该铀矿床成矿物质来源,对采自大茶园铀矿床中的脉石矿物开展了系统的C-O和Sr-Nd同位素研究。结果表明,成矿流体中矿化剂∑CO₂主要来源于地幔,部分来自于基底大理岩或沉积碳酸盐岩碳;成矿期后方解石碳同位素组成靠近基底大理岩或沉积碳酸盐岩组成,可能主要为壳源碳酸盐岩的贡献;成矿期流体中∑CO₂以HCO₃^-为主,CO₂去气作用为方解石沉淀形成的主要机制。成矿期不同阶段方解石与萤石的Sr、Nd同位素组成没有明显差别且变化较小,显示矿床中脉石矿物的同源性。通过与基底陈蔡群变质岩和盖层火山岩的Sr、Nd同位素组成对比发现,成矿期萤石与盖层火山岩具有类似的Sr同位素组成,表明大茶园铀矿床成矿物质以壳源为主,主要来自于赋矿火山岩,而Nd同位素进一步表明成矿物质可能来源于赋矿的流纹岩。岩石圈伸展控制着富CO₂热液的形成,富CO₂热液在上升过程中萃取壳源（尤其是富铀火山岩）中成矿物质,并在有利的成矿部位通过CO₂去气作用导致铀沉淀成矿。更多还原

【Abstract】 Gan-Hang uranium metallogenic belt is the largest volcanic-type uranium metallogenic belt in China. The Dachayuan（ No. 661） uranium deposit,one of the most important uranium deposits in the Dazhou uranium orefield,is located in the eastern part of Gan-Hang uranium metallogenic belt,with the orebodies existent in the Late Mesozoic rhyolite of Jiuliping Formation,Moshishan Group. In order to define the source of metallogenic matter at the Dachayuan uranium deposit,C,O,Sr and Nd isotopic compositions of hydrothermal minerals（ including fluorite,calcite） associated with uranium mineralization were systematically analyzed in this paper. The results show that the mineralizer ∑CO2 in the ore-forming fluid was mainly derived from the mantle,and partly from the marble of Chencai Group or the sedimentary carbonate; the post-mineralization calcites have the similar carbon isotopic compositions with the marble of Chencai Group or the sedimentary carbonate,indicating the main contribution of crust-derived carbonate rock. A quantitative mode simulated for the formation of calcites shows that the mineralizer ∑CO₂ in metallogenic fluid mainly occurs in the form of HCO₃^-,and the degasification of CO₂ is the main precipitation mechanism of calcite. The Sr and Nd isotopic compositions of gangue minerals in different stages are similar and fall in a narrow range,indicating a uniform and homogenous origin of Sr and Nd isotopes. In comparison with that of metamorphite from Chencai Group and volcanic rocks from Moshishan Group,the compositions of Sr and Nd isotopes indicate that the metallogenic matter of the Dachayuan uranium deposit may be mainly derived from crust,and the Nd isotopic composition further shows that the ore material might come from the rhyolite of the Jiuliping Formation. The CO₂-rich fluid that formed by the lithospheric extension,can leach the ore-forming matters from crust-derived rocks（ especially the uranium-rich volcanics） during the rising process,and finally uranium precipitated in the favorable position through the degasification of CO₂.更多还原