花岗岩型铀矿床成矿分带特征及其在下庄矿田隐伏矿床预测中的应用

摘要

花岗岩型铀矿通常形成于地台活化或地洼阶段的晚期，标志陆壳经历了多次的熔融(重熔)。对下庄矿田的热液蚀变类型及其与铀成矿关系的研究表明：含铀流体是从经历多次熔融产生的晚期岩浆系统中排出的贫硫富氧(氟、氯、二氧化碳)的热液流体；含铀热液在向上运移过程中，随着温度降低，伴生矿物析出顺序总体为氧化物–氟化物–碳酸盐–水化物，而沥青铀矿的沉淀析出主要发生在第一阶段(氧化物)后期和第二阶段(氟化物)，到第三阶段(碳酸盐)基本完成；相应的铀矿化自下而上有高温无矿带–大脉带–线脉带–网脉带–低温无矿带的分带特征。据此并结合下庄矿田 XXX 矿床的资料，提出该矿目前探明的以晶质铀矿为主的线脉矿体下方，极有可能存在沥青铀矿大脉带的定位预测方案。%Granite-type uranium deposits commonly formed in the latest stage of platform-reactivation period, which were products of multiple crustal melting (or remelting). Studies of hydrothermal alteration and related uranium mineralization indicate that U-bearing fluid was derived from magma system characterized by multiphase melting (or remelting); and the ore fluid was sulfur-deficient and vapor-rich. With decreasing temperature during the ascent of the U-bearing hydrothermal fluid, precipitation of minerals follows the order of oxides-fluorides-carbonates-hydrates. Deposition of pitchblende starts in the late oxide-stage and ends in the carbonates stage. The ore-vein types vary in the order of high temperature barren zone-large vein zone-veinlet zone-anilox zone-low temperature barren zone from the depth upwards. Combining the zoning characteristics and the geological, geochemical and geophysical data, we propose a prediction scenario for the concealed ore-bodies in the No.XXX deposit, the Xiazhuang ore-field.