摘要
硅碳泥岩型铀矿床是我国铀矿床的主要类型之一。地下水在这类矿床的形成过程中,对铀的活化、迁移和沉淀富集都起着重要的作用。这类矿床地下水中铀的存在形式及沉淀条件的研究,是其成矿规律研究的重要组成部分。文中对四个矿床的地下水资料进行分析研究。确定了铀的五种存在形式及其沉淀的物理化学条件。
Carbonate-Siliceous-pelitic rock type uranium deposits constitute one of the major types of uranium deposits in China. Underground water plays an important role in mobilization, migration, precipiation and enrichment of uranium during the formation of this sort of deposits. The investigation of modes of occurrence and precipitation conditions of Uranium in underground water is of great importance in the study of Its metallogenic regularity. Based on an analysis of data on underground water from four uranium deposits in Devonian and Sinian-Cambrian of South China, it is concluded that there exist five modes of occurrence of uranium, i. e. UO_2^(2+), UO_2OH^+, UO_2(OH)_2, UO_2(CO_3)_2^(2-) and UO_2(CO_3)_3^(4-), with the last two forms being dominant and making up over 99%. Nevertheless, the ratios between these two forms are different in water samples of different components and types. The paper points out that uranium substances of different modes of occurrence have different precipiation conditions whereas uraniferous underground water solution of the same concentration will form uranium minerals of different oxygenous coefficients under different reduction conditions. Eh (pH) value for the formation of uranium minerals with low oxygenous coefficients is somewhat higher, whereas that for the formation of uranium minerals with high oxygenous coefficients is a bit lower. The Eh value for the precipitation of uranium minerals is related to the pH value of underground water solution: Eh values for the precipitation of uranium of different modes of occurrence are in the range of 0-350 mV, while the range of pH values is 6-8. The Eh (or pE) value for the precipitation of uranium minerals is also related to the concentsation of UO_2^(2+) in the solution: in solution with high concentration, the Eh (pE) value for the formation of uranium minerals is a bit higher, and in solution with low concentration, the value is lower. All the precipitation points of uranium with various modes of occurrence in underground water form a zone rather than a line or a plane in space, which is in accord with the fact that ura(?)um deposits lie withi(?) a certain elevation range and have a definite vertical extension. This accounts for the phenomenon that uranium mineralizations in some deposits, especially in typical leaching type uranium deposits, are restricted to a certain elevation range.
出处
《矿床地质》
CAS
CSCD
北大核心
1992年第1期76-84,共9页
Mineral Deposits
