华北地台重要金矿成矿过程中的流体作用及其来源研究  

Fluids and Their Sources for Gold Mineralizations in the North China Platform

作　　者：胡受奚[1] 赵乙英[1] 孙景贵[1] 凌洪飞[1] 叶瑛[2] 卢冰[1] 季海章[3] 徐兵[4] 刘红樱[1] 方长泉[1] 

机构地区：[1]南京大学地球科学系,内生金属矿床成矿作用国家重点实验室,南京210093 [2]浙江大学地球科学系,杭州310027 [3]东京大学地球科学系 [4]东京大学地质研究所

出　　处：《南京大学学报（自然科学版）》2002年第3期381-391,共11页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金 (4 973312 0 )

摘　　要：中生代是华北地台金矿床的最重要成矿时期 ,该时期的金矿床与煌斑岩和花岗岩类密切伴生 .煌斑岩以富金和富LILE为特征 ,而花岗岩的金含量则甚低 .金矿床的铅、氢、氧和硫同位素组成高度分散 ,表明成矿物质具有多来源性 .金矿床中的蚀变时间上从早到晚的演化和空间上从下到上的分带为 :由气化 -高温 (30 0℃～ 4 5 0℃ )阶段的钾长石化 ,经 (高 - )中温(2 0 0℃～ 32 0℃ )阶段的黄铁绢英岩化和绢英岩化 ,变为中 -低温 (2 2 0℃～ 15 0℃ )阶段的硅化 .金在钾交代阶段活化转移 ,而在黄铁绢英岩化阶段开始沉淀成矿 .欧亚板块与古太平洋板块之间以及华北板块与华南板块之间在中生代时期的强烈碰撞、挤压和俯冲造成了华北地台金矿床形成的有利构造环境 .俯冲板块俯冲过程中的去气、去碱、去硅和去LILE(包括金 )等作用 ,可形成含金成矿流体 .在俯冲板块进入地幔后 ,含金流体和分熔产物一起上升并交代地幔楔 ,形成能够产生富金煌斑岩浆的富集地幔 .同时 ,仰冲板块中的褶皱、变质、花岗岩的形成、火山作用、煌斑岩侵入、水 /岩反应 ,以及成矿物质的活化转移和交换作用 ,促进了金在有利环境中聚集成矿 .The Mesozoic is the most important era to gold minelization in the North China platform. Gold deposits formed during this period are closely associated with lamprophyres and granitoids. The lamprophyres are characterized by high concentrations of gold and LILE, whereas the granitoids are poor in gold. Scattered distribution of lead, hydrogen, oxygen and sulphur isotopes in the gold deposits is possibly indicative of diverse sources of ore_forming materials. Temporal evolution and spatial zoning are common in the deposits. Typical alteration products change ,temporally and spatially with an ascending order, from potassium feldspathization of the pneumato_hydrothermal(300 ℃～450 ℃)stage, through beresitization and phyllitization of the (high_)mediantemperature?(200 ℃～320 ℃)stage, to silicification of the median_low temperature(220 ℃～150 ℃)stage. Gold could be mobilized during potassium metasomatism and started to precipitate to form ores at the beresitization stage.\;A favourable tectonic environment for gold mineralization in the North China platform was created by intense Mesozoic collision and convergence between the Eurasian and Palaeo_Pacific plates, and the North China and South China plates. Gold_bearing fluids could be produced by degassification, dealkalization,desilicification and LILE?(including gold)_releasing during subduction of a plate. When the down_going plate enters the mantle, gold_bearing fluids accompanied by partial_melting products will rise and react on the mantle wedge, resulting in an enriched mantle that is fertile for the generation of gold_rich lamprophyre magma. In the mean time, folding, metamorphism, granite formation, volcanism, lamprophyre intrusion, water/rock interaction as well as mobilization and exchange of ore_forming materials, will facilitate concentration and ore_formation of gold in favourable environments. Finally, a metallogenic model of gold is established for subduction zones.

关 键 词：华北地台 金矿 流体作用 构造环境 俯冲作用 成矿模式 

分 类 号：P618.51[天文地球—矿床学]