浙江大桥坞铀矿床铅、氢、氧同位素研究

Studies on lead,hydrogen and oxygen isotopes of Daqiaowu uranium ore-deposit,Zhejiang province

浙江大桥坞矿床是赣杭火山岩铀成矿带重要的铀矿床之一。本文通过对大桥坞铀矿床铅、氢和氧同位素及前人资料的综合研究,探讨了矿床成矿流体和成矿物质来源。结果表明花岗斑岩、凝灰岩、辉绿岩、矿石中黄铁矿、蚀变围岩中黄铁矿的Pb同位素组成变化较小,可能指示它们具有相似的源区。在铅同位素构造环境判别图解中,铅同位素投影点分布范围较广,但多数集中于地幔和造山带演化线之间,偏向造山带,反映了铅的来源与岩浆活动有关。氢、氧同位素组成显示,成矿流体主要来自大气降水。成矿物质来源于壳幔混合源。

Daqiaowu deposit is one of the important uranium deposits located in the Ganzhou-Hangzhou metallo- genetic belt of volcanogenic uranium deposits. Based on studying of the lead, hydrogen and oxygen iso- topes and predecessors data of the deposits, this paper discussed the origin of the ore-forming fluid and source of ore-forming materials of the deposits. The Pb isotopic compositions of pyrites from granitel poiphyry, tuff, diabase, ore and altered wall rocks show a slight variation, implying that the Pb isotopes may have analogous origins. In the Pb isotopes tectonic setting discrimination diagram, the plots of lead iso- topes show a widespread distribution range, but mostly concentrate between mantle evolution curve and orogenic belt evolution curve, indicating that the source of lead isotopes is related with magmatism. The hydrogen and oxygen isotope compositions show that the ore-forming fluid is originated from the meteoric water. The ore-forming materials are mainly derived from the crust-mantle mixed source.