| 大厂锡多金属矿田铜坑-长坡矿床流体包裹体研究 |
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| 引用本文：.2005.Fluid inclusion studies of Tongkeng_Changpo deposit in Dachang polymetallic tin orefield[J].Mineral Deposits,24(3):228~241 |
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| 基金项目:华锡集团有限责任公司博士后工作站科研项目“丹池成矿带构造控矿规律研究” |
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| 中文摘要:铜坑-长坡锡石硫化物矿床是桂西北大厂矿田中的一个超大型矿床，由浅部的脉状矿体和中-深部的层状矿体组成。文章应用显微测温和激光拉曼光谱分析对铜坑-长坡矿床进行了系统的流体包裹体参数和成分的测试。结果显示，铜坑-长坡矿床脉状和层状矿体的流体包裹体具有相同特征，包裹体的类型主要有CO2型和NaCl_H2O型。3个成矿阶段的均一温度分别为：270～365℃，210～240℃和140～190℃。早阶段（Ⅰ、Ⅱ阶段）成矿流体成分主要为CO2和H2O，含少量CH4和H2S，密度为0.324～1.093 g/cm3，盐度 w (NaCleq )主要集中于1%～7%；晚阶段（Ⅲ阶段）成矿流体成分主要为H2O，且Ca2+ 和Mg2+ 含量增加，密度为0.893～0.972 g/cm3，盐度 w(NaCleq )主要集中于3%～10%。流体包裹体特征和He、Ar、S同位素组成共同表明，铜坑-长坡矿床脉状及层状矿体具有相同的成矿物质来源和相同的成因，成矿作用与燕山期构造、岩浆热事件有关。基于 3He/4He比值高和富CO2流体的存在，认为在铜坑-长坡矿床成矿过程中有深部地幔流体的参与。 |
| 中文关键词:地球化学 流体包裹体 成矿作用 锡石硫化物矿床 铜坑_长坡 广西 |
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| Fluid inclusion studies of Tongkeng_Changpo deposit in Dachang polymetallic tin orefield |
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| Abstract:The Tongkeng_Changpo cassiterite_sulfide deposit in Guangxi, a superlarge deposit in the Dachang polymetallic tin orefield, is the key to the genetic study of the Dachang ore field. The Tongkeng_Changpo deposit is composed of vein_type orebodies at the upper part and stratiform ones at the bottom. Its genesis has been in debate for a long time. Some researchers hold that the deposit was formed by replacement of hydrothermal solution derived from Yanshanian granites. Others consider that it was formed by submarine exhalation in Devonian. In order to further study the origin of the ore_forming fluids and the ore genesis, the authors systematically analyzed the parameters of fluid inclusions and S isotopic components of the samples from different parts of the orebodies on the basis of the study of He_Ar isotopic components. The following three major stages in the Tongkeng_Changpo deposit have been distinguished: StageⅠ (cassiterite, sulfide, tourmaline, quartz), StageⅡ_the main sulfide stage (cassiterite, sulfide, sulfosalt, quartz, calcite) and Stage Ⅲ_ the calcite stage. Fluid inclusions of the Tongkeng_Changpo deposit can be divided into two types: CO2_type and NaCl_H2O type. The homogenization temperature is 270℃ to 365℃, 210℃ to 240℃, and 140℃ to 190℃ for StageⅠ, Ⅱ, and Ⅲ, respectively. The composition detected by Laser Raman Spectroscopy indicates that fluid inclusions at the early stage (StageⅠ and Stage Ⅱ) are enriched in CO2, with minor amounts of CH4 and H2S, whereas those at the late stage (Stage Ⅲ) are enriched in H2O. At the early stage the density of fluid inclusions is between 0.324 and 1.093 g/cm3, and salinity mainly between 1 and 7wt%NaCl equiv. At the late stage, however, the density of fluid inclusions is between 0.893 and 0.972 g/cm3, and the salinity mainly between 3 and 10 wt%NaCl equiv. δ34S values of pyrites range from -2.8‰ to -6.0‰ in the vein bodies, and from -3.9‰ to -4.7‰ in the stratiform bodies. These data show that S_forming veins and stratiform bodies are of the same source. The same fluid inclusion characteristics and the same He_Ar and S isotopic composition indicate that ore veins and stratiform orebodies in the Tongkeng_Changpo deposit are of the same origin, and both of them are related to Yanshanian magma_thermal activity. The high R/Ra ratio and CO2_enriched fluids imply that deep source fluids from the mantle might have participated in the formation of the Tongkeng_Changpo deposit. |
| keywords:geochemistry, fluid inclusions, metallogenesis, cassiterite_sulfide deposit, Tongkeng_Changpo, Guangxi |
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