中国自然铜矿床类型、特征、分布及形成条件

近年来的找矿进展显示,我国至少存在2种以上成因类型的自然铜矿床(矿化带):火山-沉积碎屑岩型和陆相砂页岩型等,其主要分布在扬子地块西南缘和新疆天山地区.以湘西九曲湾(麻阳)铜矿和滇东北沿河铜矿为例,结合国外典型自然铜矿床(矿化带),分析了自然铜的成矿学特征及形成条件.通过对比分析沉积砂岩铜矿(硫化物)与自然铜矿的成矿学特征,认为自然铜成矿必须具备3个条件:①孔隙度丰富而适宜的储矿岩石;②水-岩反应中有利于含铜岩石的萃取和运移的浅成低温热液(卤水);③贫硫富生物有机质的地球化学还原障壁带.研究显示,自然铜形成于碱性贫硫的还原环境中,生物有机质对自然铜的成矿起重要作用,相对封闭的成矿环境、独特的流体性质对自然铜起保护作用.我国南方的自然铜矿床一般显示出层控、浅成低温及生物有机质参与成矿等特点.最后探讨了自然铜矿床在我国的找矿勘探前景.

Types,Distribution and Ore-Forming Characteristics of Native Copper Deposits in China

Industrial types of copper deposits consist mainly of volcano-sedimentary and sedimentary sandstone copper deposits. These deposits are related respectively to volcano-hydrothermal solution, hydrothermal metasomatism/hydrothermal sedimentation. As a special industrial type of copper resources, native copper is formed under a weak alkalic and sulphur-deficient deoxidized environment. Three conditions are necessary during ore formation, i. e. , appropriate-porosity ore-hosted rocks, extraction and migration for epithermal organic matter-enriched hydrothermal solution during water-rock reaction and deoxidized sulphur-deficient barrier belts. This paper analyses the relationship between organic matter and ore formation of copper. The study shows organism and/or organic matter plays an important role for deoxidization and concentration of native copper. However it remains to be further researched and confirmed whether there exists the organism and/or organic matter type copper deposit. Native copper deposits in South China generally display stratabound and epithermal metallogenesis involved in organic matter. This type of deposit is typical of large-area epithermal metallogenesis in the southwestern Yangtze block since the Mesozoic. Finally, the paper discusses prospecting and exploration for native copper deposit in China.