呷村黑矿型矿床高^(18)O成矿流体的成因  

Origin of High ^(18 )O Ore-Forming Fluids in Gacun Kuroko Deposit

作　　者：余金杰[1] 侯增谦[1] 曲晓明[1] 

机构地区：[1]中国地质科学院矿床地质研究所,北京100037

出　　处：《岩石矿物学杂志》2000年第4期382-389,共8页Acta Petrologica et Mineralogica

基　　金：地矿部九五科技攻关课题!<义敦岛弧构造演化与多金属矿成矿规律>的部分成果

摘　　要：本文基于流体包裹体和石英18O资料 ,提出呷村高18O成矿流体的成因有两种可能性 :一种 ,指示岩浆流体的参与 ,这已被成矿流体的高盐 [w (NaCleq) =5.7%～ 2 1.3% ]和极度富气所证实。另一种 ,指示海水与高18O火山岩或沉积岩发生过高温、低m水/m岩石 反应。现代和古代VMS矿床热液对流深度、水 -岩反应理论计算结果及遍布矿区成矿前的低温 ( <150℃ )和高m水/m岩石 反应表明后一种可能性的存在。高18O成矿流体来源的确对完善VMS矿床成因模式具有重要意义。Based on fluid inclusion and oxygen isotope data, this paper holds that high 18 O ore forming fluids were formed by mixture of magmatic fluid and evolved seawater. High salinity [ w (NaCl eq )=5.7%～21.3%] and rich gas indicate the contribution of magmatic fluid to ore forming fluids. Background felsic volcanics at Gacun are extremely enriched in 18 O compared to isotopically normal felsic rocks (14.2‰～17.5‰ vs 6‰～10‰).This has been interpreted in terms of pervasive and widespread exchange with marine water under the condition of low temperature and a high water/rock ratio, which supports the mineralogical evidence of intense hydrothermal alteration. Wholerock δ 18 O values of stockwork samples from Gacun orebodies are relatively uniform (10.5‰～13.1‰), showing depletion of 18 O relative to the other Gacun volcanics less intensely affected by the ore_forming solutions. These relations signify that the ore_forming process postdated the early hydrothermal event that enriched the Gacun volcanics with 18 O. The present δ 18 O values of 10.5‰～13.1‰ for the stockwork rocks are therefore believed to have been reached through two successilve stages of hydrothermal alteration: early 18 O enrichment to values near 16.2‰ in the regional,pervasive and low temperature event, followed by 18 O loss to around 10.5‰～13.1‰ induced by evolved marine water in stockwork vents.

关 键 词：黑矿型矿床 水-岩反应 成因 氧同位素 成矿流体 

分 类 号：P618.301[天文地球—矿床学] P611[天文地球—地质学]