诸广岩体南部铀矿区稳定同位素组成及矿床成因分析

摘要

Southern Zhuguangshan pluton has produced several large uranium deposit. In this paper ,the composition of sulfur ,hydrogen and oxygen was studied to discuss the origen of metallogenic fluids and source matterials. The analysis results shew that the δ34 SCDT values of pyrites from uranium ore vary from -17.4‰ to -17.9‰ which is quite different to that from the diabase ranged from -0.5‰ to -0.2‰. This suggest that sulfur in the mineralizing fluid is unlikely from the mantle. InδD-δ18OH2O di‐agram ,charater value of hydrogen and oxygen isotopes composition of mineralizing fluid fall into the re‐gion between mantle water ,magama water ,matmophic water and the meteoric water which furthermore indicate the meteoric origen of mineralization fluid. The carbon isotopic composition vary from -9.8‰to -4.3‰ ,which suggests that the carbon was derived from the granite. The isotopic feature discussed above ,may tell us that the mineralizing fluid in the study area was derived from the meteoric water which run into the deep along the fractures and extracted various kinds of elements from surrounding rock (including granite).%诸广岩体南部产出多个大中型铀矿床，笔者通过测定各主要矿床的硫、氢、氧同位素组成，探讨成矿流体和成矿物质来源。研究发现，富矿石中黄铁矿的δ34 SCDT值为－17.4‰～－17.9‰，与新鲜辉绿岩中黄铁矿的δ34 SCDT值（－0.5‰～－0.2‰）明显不同，表明成矿流体来自幔源的可能性很小。在δD－δ18 O H2 O图中，所有氢、氧同位素组成特征值均落于地幔水、岩浆水、变质水与大气降水线之间，进一步表明成矿流体来自大气降水。δ13 C PDB值为－9.8‰～－4.3‰，显示碳很可能来自花岗岩。上述同位素特征表明，区内与花岗岩有关的脉型铀矿床可能主要由大气降水沿深大断裂循环并萃取围岩（包括花岗岩）中各种成矿元素而形成。