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1220铀矿田位于破火山口中。本文对流体包体和硫、氧、碳同位素进行了研究,对成矿模式和钍在热液中的地球化学特点进行了讨论。成矿温度在矿前期、成矿期和矿后期分别为271-330℃,115-275℃和室温-194℃。成矿压力约为500巴。流体包体分析表明,气相中以H_2O为主,其次为CO_2和N_(23)液相中阳离子Na~+>K~+,Ca~(2+)>Mg~(2+),阴离子在矿前期和矿后期以HCO_3~-为主,成矿期以SO_4~(2-)为主。pH_(50℃)矿前期为9.36-9.41,成矿期为7.91,矿后期为8.57-8.87。成矿期热液的盐度为15wt％,密度为0.993克/厘米~3。矿床中硫化物的δ~(34)S为-3.1-+17.3‰,δ~(18)OH_2O的平均值在矿前期、成矿期和矿后期分别为4.51,-2.08和-2.96‰,δ~(13)C的平均值在矿前期、成矿期和矿后期分别为-4.42,-2.10和-6.49‰。上述同位素资料表明,含矿溶液可能为岩浆成因的溶液与大气降水的混合物,但据δ~(18)OH_2O资料,矿前期主要为岩浆热液,成矿期和矿后期主要为渗流热液。本文还讨论了铀、钍的来源、搬运形式和沉淀机理。作者指出,钍可以在强碱性热液条件下迁移富集,并对它作了某些解释。同时作者提出该类矿床的有利地质找矿标志。
The 1220 uranium field is located in the caldera. In this paper, fluid inclusions and sulfur, oxygen and carbon isotopes are studied, and the metallogenic model and the geochemical characteristics of thorium in hydrothermal fluids are discussed. The metallogenetic temperature is 271-330 ℃, 115-275 ℃ and room temperature -194 ℃ in the pre-ore stage, ore-forming stage and post-ore stage respectively. Mineralization pressure is about 500 bar. The analysis of fluid inclusions showed that H_2O was the main phase in the gas phase, followed by Na + K +, Ca 2+ + Mg 2+ in CO_2 and N_ (23) In the early and late stages, HCO_3 ~ - is the dominant type, and SO_4 ~ (2-) dominated the mineralization. The pH_ (50 ℃) pre-deposit is 9.36-9.41, the metallogenic period is 7.91 and the post-ore deposit is 8.57-8.87. The mineralization salinity is 15wt% and the density is 0.993g / cm ~ 3. The δ ~ (34) S of the sulfide in the deposit is -3.1- + 17.3 ‰, and the average value of δ ~ (18) OH_2O is 4.51, -2.08 and -2.96 ‰, respectively in the pre-ore stage, ore-forming stage and post- The average value of ~ (13) C was -4.42, -2.10 and -6.49 ‰ respectively in the pre-ore stage, mineral-forming stage and post-ore stage. The above isotopic data show that the ore-bearing solution may be a mixture of magmatic causative solution and atmospheric precipitation. However, according to the data of δ ~ (18) OH_2O, the pre-ore stage is mainly magmatic hydrothermal fluid, and the mineralization and post-ore stage are mainly seepage hydrothermal fluids. This article also discusses the sources of uranium, thorium, handling patterns and sedimentation mechanism. The authors note that thorium can be migrated and enriched under strongly alkaline hydrothermal conditions and some explanation has been given to it. At the same time, the authors put forward favorable prospecting signs for this type of deposit.