诸广岩体南缘长江矿田铀矿成矿机理探讨

Metallogenic mechanism of uranium deposits in the Changjiang orefield on the south margin of Zhuguang rock body

长江矿田位于诸广岩体南缘,矿田内铀矿化类型主要为硅化带型和交点型。通过分析长江矿田内主要的赋矿花岗岩地球化学特征,矿床成矿期的石英、方解石以及黄铁矿的稳定同位素组成。认为长江矿田内赋矿花岗岩主要由南岭地区基底变质岩部分熔融形成,部分熔融的物质由变质泥质岩逐渐转变为变质杂砂岩;南岭地区基底变质岩及其部分熔融形成的花岗岩具有较高的U含量以及与萤石拥有相似的εNd(t)值,而基性岩脉中不仅铀含量偏低,且εNd(t)值(平均为1.4)明显不同,所以长江矿田内成矿物质来源于南岭地区基底变质岩及其部分熔融形成岩花岗岩;成矿热液是由地幔流体在上升侵位过程中,与大气降水混合形成的。

The Changjiang orefield is located in the southern margin of Zhuguang rock mass.The main types of uranium mineralization in this area are silicified zone type and intersection type.By analyzing the geochemical characteristics of the main ore-bearing granites in the Changjiang ore field,the stable isotopic compositions of quartz,calcite and pyrite formed during the mineralization of the deposit are analyzed.It is considered that the ore-hosting granites in the Changjiang orefield are mainly formed by partial melting of basement metamorphic rocks in Nanling area,and the partially melted materials are gradually transformed from metamorphic argillaceous rocks to metamorphic complex sandstones.The basement metamorphic rocks and their partially melt-formed granites in Nanling area have high U content and similar values ofεNd(t)with fluorite.The uranium content in basic dikes is not only low,but alsoεNd(t)value(average is 1.4)is obviously different.Therefore,the ore-forming materials in the Changjiang orefield are derived from the basement metamorphic rocks in Nanling area and their partially melted granites.Metallogenic hydrothermal fluid is formed by the mixing of mantle fluid and atmospheric precipitation in the process of ascending emplacement.