粤北仙石铀矿床的铅、碳、硫同位素研究

Lead, Carbon and Sulfur Isotopic Compositions of the Xianshi Uranium Deposit, Northern Guangdong Province

仙石铀矿床位于粤北贵东复式花岗岩体东部,矿体赋存于NWW向辉绿岩与NEE向硅化带交接部位。矿床中黄铁矿以富集放射成因铀铅为特征,3组比值分别为(206Pb/204Pb)i=18.756～23.883,(207Pb/204Pb)i=15.676～15.932,(208Pb/204Pb)i=38.530～38.938,主要位于基底变质岩铅范围内;矿床中方解石δ13C值为-8.5‰～-3.1‰,相似于地幔值((-5±2)‰);黄铁矿δ34S值为-10.1‰～-8.3‰,它与花岗岩中黄铁矿δ34S值(-10.9‰～-7.1‰)相似,而与辉绿岩中黄铁矿δ34S值(-0.03‰～2.1‰)区别明显。上述同位素特征表明仙石铀矿床的成矿物质具多源特征。

The Xianshi uranium deposit is located in the eastern part of the Guidong composite granite body. The uranium ore bodies occur in the intersection parts of the NWW-trending diabase dikes and the NEE-trending sillicification zones. The pyrite in the deposit is characterized by enrichment of radiogenetic uranium lead, ( 206Pb/ 204Pb)_i=18.756~23.883, ( 207Pb/ 204Pb)_i=15.676~15.932 and ( 208Pb/ 204Pb)_i=38.530~38.938, mainly plotted in the range of the basement metamorphite lead. The calcite of uranium deposit has δ 13C values of -8.5^-3.1‰, which coincides with the mantle δ 13C values (-5±2‰). The δ 34S values of pyrite ( -10.1 ~ -8.3‰) is close to the δ 34S values of pyrite in the granite (-10.9^-8.1‰) and markedly different from the δ 34S values of pyrite in the diabase dike (-0.03~2.1‰). Based on the lead, carbon and sulfur isotopic signatures, it is proposed that the ore-forming materials of the Xianshi uranium deposit display multiple-resourced characteristics.