【摘要】 长江铀矿田深部赋矿辉长闪长岩的岩石成因制约着对铀成矿作用认识的深入.通过对辉长闪长岩开展锆石U-Pb定年、Lu-Hf同位素、矿物学和地球化学分析,探讨其岩石成因、成岩构造背景及其与铀成矿的关系.辉长闪长岩LA-ICP-MS锆石U-Pb年龄为150 Ma,形成于晚侏罗世,具板内玄武岩地球化学特征.环带斜长石与黑云母主量元素变化记录了岩浆由基性到中性的演化过程.锆石（～150 Ma）ε_Hf（t）为-14.1～-8.6,t_DM2为1.7～2.1 Ga.辉长闪长岩源区为遭受俯冲带流体交代改造的相对富集地幔,岩浆上升侵位过程与中元古代-古元古代壳源物质发生了不同程度的地壳混染,形成于地壳伸展拉张和岩石圈大规模减薄的构造背景.辉长闪长岩为铀成矿提供了更为有利的还原性环境,促使热液中U⁶⁺的还原沉淀.更多还原

【Abstract】 Understanding for uranium mineralization was absolutely restricted by the petrogenesis of gabbro-diorite, which emplaced into the Yanshanian biotite granite at the deep part of Changjiang uranium ore-field. We provide LA-ICP-MS zircon UPb age, Lu-Hf isotopic, mineralogical and geochemical evidence to analyse the poetrogenesis, tectonic background and its relationship with uranium mineralization. Gabbro-diorite emplaced at the Late Jurassic（LA-ICP-MS zircon U-Pb isotopic age:150±1 Ma（n=17,MSWD=0.18）） and was geochemically characteristic of within-plate basalt. The magma evolution process（ranges from basic to neutral magma） has been effectively recorded by the transformation of major elements in zoned plagioclase and biotite from gabbro-diorite. The zircon ε_Hf（t） values range from-14.1 to-8.6 and the two-stage model ages(t_DM2) range from1.7 Ga to 2.1 Ga. The magmatic source was the relatively enriched mantle changed by the metasomatism fluid originated from the subduction zone of Pacific Ocean Plate which started from the Middle Jurassic. Gabbro-diorite has undergone a variational degree crustal contamination with the Proterozoic-Palaoproterozoic crustal material in the process of emplacement during the Late Mesozoic large scale lithosphere thining tectonic background. Gabbro-diorite provides a better reductive environment than the granite for uranium mineralization, prompting U⁶⁺ been reduced to pitchblende in the ore forming hydrothermal fluid.更多还原