某钼-铀矿床矿化特征及成因类型探讨

矿床产于中元古代地层中。矿区内酸性脉岩发育,常密集成带,矿床受穿过脉岩带的构造破碎带控制。矿化岩石主要为构造碎裂岩和角砾岩,其原岩为长英质脉岩、变石英砂岩、变安山岩、板岩及粉砂岩等。矿化以裂隙充填为主,对围岩化学成分的选择性不大。围岩蚀变有:绢云母化、硅化、钾长石化、黑云母化、黄铁矿化、赤铁矿化及水合多水高岭石化等。铀矿物主要为沥青铀矿、铀黑、铀石,其次有钛铀矿、水铀矾,含铀矿物有锐钛矿、金红石、赤铁矿、水合多水高岭石和褐铁矿等;其它金属矿物主要有辉钼矿、黄铁矿、方铅矿和黄铜矿。矿石具脉状、角砾状、块状和浸染状构造,沥青铀矿具胶状结构。矿床中钼的储量远大于铀,铀矿体产于钼矿体之中或其边部。通过室内、外研究,可以认为本矿床为与中酸性小侵入体有关的中-低温热液成因的钼-铀型复合矿床。

ON THE CHARACTERISTICS OF MINERALIZATION AND GENESIS OF A MOLYBDENUM-URANIUM DEPOSIT

The deposit occurs in the Middle Proterozoic strata where veins of acidic rocks are developed and often densely grouped in zones. It is controlled by fractured zones cutting through vein zones. Host rocks are mainly cataclastite and breccia which are derived from felsic veins, meta-quartzose sandstone, meta-andesite, slate and siltstone, etc. Mineralization is present predominately in the form of fracture fillings and it has no close relation with chemical compositions of the wall rock. Wall rock alterations include sericitization, silicification, potassic feldspathization, biotitization, pyritization, hematitization and hydrous kaolinization. Uranium minerals comprise mainly pitchblende, uranium black, coffinite, with minor brannerite and zippeite. Uraniferous minerals are anatase, rutile, hematite, hydrous kaolinite and limonite, etc. Other metallic minerals are essentially molybdenite, pyrite, galena and chalcopyrite. The uranium ores exhibit veinlike, brecelated, massive and disseminated structures and pitchblende has colloform texture. Molybdenum reserves in the deposit are much more than uranium reserves. The uranium orebodies occur within or at the margin of the molybdenum orebodies. Laboratory and field studies show that this deposit may be considered as a molybdenum-uranium composite deposit of meso-and epithermal origin associated with intermediate acidic small intrusions.