隐爆角砾岩型金矿床的研究进展

文章阐述隐爆角砾岩型金矿床的定义、成矿构造背景、隐爆角砾岩及其矿床特征、成矿流体特征以及隐爆角砾岩成岩-成矿模式等方面研究进展。隐爆角砾岩型金矿床多产于古老地块活化区、中生代断陷盆地边缘、滨太平洋岛弧火山岩带内。矿体与浅成-超浅成中-酸性斑岩具有密切的时空关系,多赋存于斑岩体的顶部。侵入岩具有富碱、富硅特征,属Ⅰ型花岗岩类。当侵入体顶部高热能流体压力大于围岩抗拉强度和最小主应力之和时发生隐爆作用而形成隐爆角砾岩。隐爆角砾岩筒垂向可分为裂隙相、震碎相、爆破相和通道相;角砾粒径从中心到边缘水平分带一般呈由小到大的趋势。成矿流体由于爆发作用瞬间由封闭体系进入半开放或开放体系,产生较大的压力梯度,流体减压沸腾、混合、不混溶和水岩反应等引起成矿元素稳定的物理化学条件变化,导致金络合物的溶解度降低而产生金矿化。隐爆角砾岩筒的形成及流体演化分别具有"自下而上-顺次推进-序次叠加"和"升温-(爆破)沸腾-降温-升温-(爆破)沸腾-降温"的演化过程,其中"沸腾-降温"阶段为矿质主要沉淀阶段。隐爆角砾岩型金矿的成矿具有"一体多型""一筒多型"的特点,运用矿床系列-成矿系统理论指导勘探找矿具有十分重要的意义。

Research progresses on cryptoexplosion breccias type gold deposits

The article summarizes the progress on concept definition,metallogenic tectonic geological conditions,and features,metallogenetic fluid characteristics and cryptoexplosive breccia diagenetic and metallogenetic mechanism of cryptoexplosive breccia and the breccia type gold deposits.Such deposit is prolific in the ancient land activation area,Mesozoic fault basin edge or island arc volcanic belt of the Pa-cific Rim.The ore body is spatially and temporally related closely to hypabyssal-ultra shallow acidic por-phyry bodies and occurs at top of the body which are alkali-rich and silicon-rich and belongs to "I" type granite.When pressure of the high heat energy thermal fluid at top of the body is greater than the sum of the tensile strength of the surrounding rock and the minimum principal stress cryptoexplosion occur and the cryptoexplosive breccia is formed.Commonly the cryptoexplosive breccia cylinder is vertically zoned as crack phase 、shattered phase、blasting phase、channel phase.Breccia size tends horizontally to be smaller from center to edge.The Instant burst of ore-forming fluid in a closed system creates a semi-open or open system and leads to relative large pressure gradient.Pressure of the ore-forming fluid is reduced and the fluid boiled.Mixture,immiscibity of the fluid and water-rock reaction change the physiochemical condi-tion and cause reduction of solubility of gold complexes and the complexes precipitate to be gold minerali-zation.Formation of cryptoexplosive breccia cylinder and evolution of thermal fluid were promoted and o-verprinted sequentially upward from the bottom in the process of “temperature increase-(explosion)boil-temperature decrease-temperature increase-(explosion)-boil-temperature decrease”.“boil-temperature de-crease”is the main ore material precipitation stage.This type of gold deposit is characterized by metallo-genic series and system.Multi-type ores occur in one intrusive body or one cylinder.It is significant to guide further exploration in the area.