相山铀矿田红卫-沙洲岩体^(40)Ar-^(39)Ar年龄及其地质意义

^(40)Ar-^(39)Ar Age and Geology Significances of Hongwei-Shazhou Pluton in Xiangshan Uranium Ore Field

应用^(40)Ar-^(39)Ar阶段升温法测年技术,笔者对相山铀矿田北部成矿带重要的赋矿岩体——红卫-沙洲似斑状花岗岩不同程度的矿化蚀变岩石进行对比研究,恢复了该岩体的热演化历史,从而也限定了该成矿带的碱性热液成矿时代。研究发现,红卫-沙洲岩体在岩浆侵位、冷却后,局部经历了碱性成矿热液活动和酸性成矿热液活动热事件;岩体在130.54±0.84Ma时冷却固结,在123.90Ma时开始经历碱性成矿热液活动,并持续至114.84±1.19Ma左右,形成早阶段的碱交代型铀矿化,之后还经历了酸性成矿热液活动。最终可以限定,相山矿田北部碱交代型铀矿的成矿年龄为123.90~114.84Ma。

Hongwei-Shazhou porphyritic granite pluton is one of the important wallrocks in the northern metallogenic belt of Xiangshan uranium ore field, the thermal history of the porphyritic granite was studied by using the stepwise heating ^（40）Ar-^（39）Ar dating technique. A comparative study on the ^（40）Ar-^（39）Ar dating of rocks with different alteration intensity were carried out and it was found that part of Hongwei-Shazhou pluton experienced alkaline hydrothermal metallogenic event and acid hydrothermal metallogenic event after magmatic emplacement and cooling. It was considered that the pluton cooled and solidified in 130.54±0.84 Ma, and experienced alkaline metallogenic hydrothermal activity from 123.90 to 120.34 Ma. The alkaline hydrothermal activity continued to 114.84±1.19 Ma, leading to the formation of early-stage alkali metasomatic type uranium deposits. The pluton also experienced acidic ore-forming hydrothermal activity after alkali mineralization. It finally came to the conclusion that the mineralization age of alkali metasomatic type deposits ranges from 123.90 Ma to 114.84 Ma in the northern Xiangshan ore field.