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含硫化物脉状矿床成矿流体的中阶段 δD亏损：实例与原因

ISSN号：0379-1726
期刊名称：《地球化学》
时间：0
分类：P597[天文地球—地球化学;天文地球—地质学] P611[天文地球—矿床学;天文地球—地质学]
作者机构：[1]中国科学院广州地球化学研究所成矿动力学重点实验室,广东广州510640, [2]北京大学造山带与地壳演化教育部重点实验室,北京100871
相关基金：国家重点基础研究发展计划项目（2006CB403500）;国家自然科学基金（40730421,40425006）;中国科学院百人计划项目第一作者作为涂光炽先生的学生,曾得到先生的悉心指导和多方面的关怀,值此先生逝世一周年之际,谨以此文表达对先生的感激和怀念.

关键词：含硫化物脉状矿床, 成矿流体, 中阶段δD亏损, 氢, 氧同位素演化, 概念性模型, sulfide-bearing lode deposit, ore fluid, middle-stage δD-depletion, H-O-isotope evolution, conceptual model

中文摘要：

很多含硫化物脉状金银矿床的成矿过程可以大致分为3个阶段，从早到晚分别以形成黄铁矿一石英组合、多金属硫化物和碳酸盐网脉为标志。所谓中阶段δD亏损，是指在成矿流体δ16O逐渐降低（或升高）时，中阶段δD同时低于早阶段和晚阶段的δD。列举了一些矿床的氢氧同位素研究结果，例证了这种现象的存在；根据中阶段伴随大量硫化物沉淀的事实，认为硫化物沉淀时流体中H2S或HS-的H＋被金属离子置换出来，H＋加入到流体系统后导致了流体的中阶段δD亏损。对不同温度H2O-H2S体系1000Inα值的概算显示，在200～650℃温度范围，H2S或HS-的6D低于H2O的δD约211‰～478‰，H2S或HS-中H＋的少量释放即可导致流体水δD的显著降低。因此建议，成矿流体从早到晚8180逐渐降低，中阶段δD亏损的规律，可以作为含硫化物脉状矿床氢氧同位素演化的概念性模型。

英文摘要：

The metallogenic process of most sulfide-bearing lode deposits includes three stages. Three generations, from early to late, pyrite-quartz, polymetallic sulfides and carbonate veinlets, were formed in these three stages, respectively. In this paper the middle-stage δD-depletion in fluid is that the δD ratio of middle middle-stage fluid is lower than those of either the early- or the late-stages along with gradual δ^18O decrease （or increase if there is）of fluid from early to late. Through listing the δ^18O and δD data of several sulfide-bearing lode deposits, the phenomenon is evidenced. Considering that the majority of sulfides precipitated in the middle stage, we believe that H＋ in I-IS- or H2S dissolved in fluid system was replaced by metallic ions, and released into fluid （water） during sulfide-precipitation, resulting in the middle-stage δD-depletion. A brief calculation of 1000lnα for H2O-H2S system in the temperature span of 200 - 650 ℃ shows that δD of H2S or HS- is lower than δD of H2O by 211‰ - 478‰. This means that, a slight H ＋-release form H2S or HS- can cause obvious δD-decrease in fluids. Hence it is suggested that the drastic middle-stage δD-depletion together with gradual δ^18O-decrease from early to late stages can be taken as a conceptual model for hydrogen-oxygen isotope evolution of sulfide-bearing lode deposits.

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