| 川西呷村黑矿型多金属矿床成矿流体化学和热演化历史与成矿过程 |
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| 引用本文：.1991.Ore Fluid Chemistry, Thermal Evolution History And Ore-Forming Process Of The Gacun Kuroko Type Polymetallic Deposit In Western Sichuan[J].Mineral Deposits,10(4):313~324 |
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| 中文摘要:川西呷村含金富银多金属矿床是典型的黑矿型Zn-Pb-Cu-Ag矿床，其形成于与岛弧裂陷相伴的“双峰式”火山活动末期，产于岛弧裂谷带内的酸性火山岩系中。矿床由下部网脉状矿和上部块状矿组成，具“双层结构”金属分带和蚀变分带特征，矿体与喷气岩-喷气沉积岩密切伴生。成矿作用可分为四个阶段，每一阶段均形成特定的矿物共生组合。本文在已往研究基础上，拟就成矿流体的化学成分和热演变历史，探讨矿床金属分带、蚀变分带机理和成矿作用过程。 |
| 中文关键词:黑矿型矿床 热演化 流体化学 成矿作用过程 |
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| Ore Fluid Chemistry, Thermal Evolution History And Ore-Forming Process Of The Gacun Kuroko Type Polymetallic Deposit In Western Sichuan |
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| Abstract:The Gacun auriferous and argeniferous polymetallic deposit in western Sichuan Provinee is a typical kuroko type Zn-Pb-Cu deposit formed at the terminal stage of “double peak type” volcanism associated with the island arc rifted depression and occurring in acid volcanic system within the island arc rifted zone. The ore deposit is composed of network ores in the lower Dart and massive ores in the upper part, characterized by “two-layer structure”, metallic zoning and alteration zoning and accompanied with exhalite and iron-rich chemical sedimentary rock. The ore-forming process of the Gacun ore deposit might be divided into four stages with each stage forming its own index mineral assemblage(phase). Homogenization temperatures of fluid inclusions indicate that ore-forming temperatures ofⅡ, III and IV metallogenic stages are respectively 260-209℃, 320-262℃and 100-185℃. Studies show that ore-forming temperatures of various metallo'genic stages and their evolution trend basically represent temperatures of ore fluids at various stages and their evolution trend. The network ore and the massive ore show similar evolution trend of fluid temperature(II-Ill-IV), revealing that the two sorts of ores lay in the same hydrothermal fluid system and were formed through the deposition of the same fluid in different environments. Chemical composttion of ore fluids was estimated by means of inclusion composition determination and thermodynamic model. aH2S of ore fluids was restricted by fluid temperature. High temperature and high aH2S characters of ore fluids at Stage III led to the dissolution and leaching of minerals of Phase I and Phase II, and the persistent precipiration of chalcopyrite and some other minerals gave birth to the initial metallic zoning. m∑SO42- of ore fluids was related to fluid composition and source. The gradual increase in m∑SO42- wi th time implies the corresponding increase in proportion of seawater composition in ore fluids, and this accounts for the appearance of large quantities of barite in Phase IV and the stable distribution of barite layer at the top of the massive ore bed. H2S concentration and cation concentration governed the crystallization order and deposition proportion of sphalerite and galena: for ore fluids of No.II metallogenic stage, m∑Zn< m∑H2S< m∑Pb, and this decided that sphalerite crystallized at first in this stage with the crystallization amount larger than that of galena. For ore fluids of No.IV stage, m∑H2S << m∑Pb or m∑Zn, which decided that crystallization amount and proportion of sphalerite and galena had nothing to do with Zn and Pb concentration of ore fluids. |
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