攀枝花大田铀矿床成矿地质特征及控矿因素

METALLOGENIC GEOLOGICIAL CHARACTERISTICS AND ORE-CONTROLLING FACTORS OF THE DATIAN URANIUM DEPOSIT IN PANZHIHUA AREA

大田铀矿床位于扬子陆块西缘康滇地轴中段,矿区内出露地层为古元古界康定群咱里组,矿体主要产于咱里组一、二段碎裂的混合岩化斜长角闪岩、含黑云母混合岩中。混合岩化斜长角闪岩型矿石w(SiO2)54.50%~57.13%,w(Na2O)2.07%~5.68%;含黑云母混合岩型矿石w(SiO2)67.31%~85.24%,w(Na2O)1.45%~4.31%,显示成矿作用伴有硅质增加和钠质交代作用。矿石稀土元素配分型式为右倾型,δEu为0.17~0.46,指示铀成矿与深熔作用晚期结晶分异形成的熔融体有关。铀矿体的形成和分布受韧—脆性构造系统、钠质交代蚀变、不同岩性结构面、含碳(石墨)层位、变质深熔作用等因素控制。电子探针数据显示,区内铀矿物主要为晶质铀矿(UO2:81.93%~86.96%)、钛铀矿(UO2:52.49%~62.41%,TiO2:16.91%~23.52%),显示高温成矿作用特点。矿床成因类型为与构造有关的变质热液矿床。

The Datian uranium deposit in the middle segment of Kangdian Axis occurs in the magmatite of Kangding Complex.The ore-hosting layer is Palaoproterozoic Zali Formation and the ores are hosted in the migmatization amphibolite and veined biotite migmatite.Geochemical analysis of the ore-bearing rocks shows that the content of w(SiO2)and w(Na2O)in migmatization amphibolite ranges from 54.50%to 57.13%and 2.07%to 5.68%respectively,and the content of w(SiO2)and w(Na2O)in biotite migmatite(vein body)ores is 67.31%-85.24%and 1.45%-4.31%respectively.The metallogenesis of uranium is associated with increase of siliceous and natritic metasomatism.The distribution type of rare earth elements of the ore is right-incline type with the Eu value ranging from 0.17 to 0.46,indicating that uranium mineralization is related to the molten body formed by crystallization differentiation in the late stage of deep fusion.It reveals that the formation and distribution of uranium ore bodies are controlled by such factors as ductile-brittle tectonic system,sodium metasomatism alteration,different lithologic structure planes,carbon(graphite)bearing horizon,and metamorphism-induced deep-fusion and so on.Electron microprobe analysis data show that the uranium minerals in the area are mainly crystalline uranium(UO2=81.93%-86.96%),titanium uranium(UO2=52.49%-62.41%,TiO2=16.91%-23.52%),characteristic of high-temperature mineralization.It is considered that the uranium deposit is a metamorphic hydrothermal deposit related to structural activity.