贵州荔波-独山地区含铀煤系地质地球化学特征及煤岩型铀矿床成因

Geological and Geochemical Characteristics of Uranium-bearing Coal Series and Genesis of Coal-type Uranium Deposits in Libo-Dushan Area,Guizhou Province

贵州荔波-独山地区含铀煤系位于二叠系吴家坪组底部黑色介壳灰岩层及深灰色硅质灰岩之上,属贵州省丹寨-三都-独山碳硅泥岩型、煤岩型铀成矿带,已发现2个达到工业品位的小型煤岩型铀矿床。本文对含铀煤层开展了地质地球化学、控矿因素及成矿机制与成因等方面研究。结果表明,研究区自北至南岩相及铀富集规律呈有规律变化,即北部海湾沼泽相矿层稳定,品位较高,中部及南部为相变过渡带及海陆交替相,矿化不够稳定,品位低;成矿物质U主要来源于火山活动,部分来自围岩,与晚二叠世吴家坪阶早期峨眉山地幔热柱海相第一喷发旋回期后,富含SiO_(2)、Mn、U、Co,Pb、CO_(2)等气液流体溶入海水有关;铀矿化形成受层位(吴家坪组)、岩性(褐煤、炭质页岩)、构造(方村向斜及南北向断裂)及沉积环境(还原、酸性-低盐)等因素控制;含铀煤属同生沉积、同生富集为主,构造叠加改造为辅的成因类型。

The Libo-Dushan uranium-bearing coal deposits,which belongs to the Danzhai-Sandu-Dushan uranium belt in the Guizhou provience,occurs between the black shell limestone and the dark grey silliecous limestone of the Permian Wujiaping formation.Two coal-type uranium deposit has been found in this area.In this paper,it investigates the geochemical characteristics,ore controlling factors and genesis of the uranium-bearing coal bed in this area.The lithofacies shows a variation that the littoral facies occurs in the north but the paralicfacies in the south.The stability and grade of uranium mineralization depress from north to south.the volcanic activity and the minor wall rocks provide the ore-forming fluids for the mineralization.The mineralization is attributed to the mixture of the sea water and the fertile hydrothermal fluids which is rich in SiO2,Mn,U,Co,Pb and CO2.This processis related to the first activity of Emeishan mantle plume during the late Permain.The uranium mineralization is limited by such factors as stratum(Wujiaping formation),lithology(the lignite,black shale),structure(Fangcun syncline and the S-N trend faults),sedimentary environment(reductive sedimentary,acidity-low salinity).The Libo-Dushan uranium-bearing coal deposits has formed by the multiple genesis which including the preconcentration during the sedimentation and the superposition of tectonic activity.