康滇地轴中南段牟定1101铀矿区沥青铀矿成矿时代及成因

牟定1101铀矿区是康滇地轴中南段发现高品位、巨粒晶质铀矿代表性产地之一.为了解铀矿物的形成时代及成因，利用微区、原位分析技术（EPMA、SEM、LA-ICP-MS）对该区3件沥青铀矿样品开展了主量化学成分、稀土元素分析及年龄测定.沥青铀矿电子探针（EPMA）化学成分具有高PbO、ThO₂、Y₂O₃，低SiO₂，Na₂O，CaO，K₂O，ZrO₂含量特征，反映沥青铀矿形成之后遭受后期的蚀变、改造作用较弱.沥青铀矿的稀土元素ΣREE-（U/Th）、ΣREE-（ΣREE/ΣREE）_N图解表明其为岩浆作用相关成因、形成于高温环境（T>450℃）.3件沥青铀矿的U-Pb同位素年龄在（950±5 Ma、MSWD=0.025，953±9 Ma、MSWD=0.051，954±8 Ma、MSWD=0.085）之间，表明它们具有相近的形成时代（新元古界晚期）.对比国外不同类型铀矿床，该区的铀成矿作用具有岩浆成因特征.新元古界晚期，Rodinia超大陆由聚合转化为裂解阶段，广泛引起了Pt₁j苴林群发生区域变质、混合岩化、铀成矿作用.牟定1101铀矿区的成矿作用与~960 Ma Rodinia超大陆裂解地质事件所对应的晋宁构造运动有关. 

Metallogenic Chronology of the Pitchblende of 1101 Uranium Ore Area in Mouding,Middle-South Part of the Kangdian Axis and Its Geological Significance

The 1101 uranium ore area is one of the representative uranium deposits, which has high-grade and larger uraninite. In order to know the genesis and metallogenic age of the pitchblende, the in-situ analytical technologies(EPMA、SEM、LA-ICP-MS) was applied to analyze the three pitchblende samples.The chemical composition of EPMA indicate that pitchblende exhibits high contents of PbO, ThO₂, Y₂O₃ and low SiO₂, Na₂O, CaO, K₂O, ZrO₂, which shows that it has suffered less alteration after crystallization.The REE diagram of(ΣREE-(U/Th), ΣREE-(ΣREE/ΣREE)_N)reflects that these pitchblend crystalized in the condition of magamatic process, related to a high temperature environment(T>450℃).The LA-ICP-MS of pitchblende U-Pb dating yields the age of (950±5 Ma, MSWD=0.025, 953±9 Ma, MSWD=0.051, 954±8 Ma, MSWD=0.085), providing the metallogenic age constraint on the 1101 uranium ore area(Late-Neoproterozoic).Compared with different types of uranium deposits abroad, the 1101 uranium ore was of magamatic origin that had undergone the process of migmatization.The Rondinia super continent was in the transition from convergence to split at the period of Late-Neoproterozoic, which led to the Pt₁j strata generated regional metamorphism, migmatization and uranium mineralization.The metallogenic age ca.960 Ma of 1101 uranium deposit corresponds to the Jinningian tectonic movement, which belongs to the Rondinia supercontinenal spilitting geological event.