变质岩区金矿成矿系统

METALLOGENIC SYSTEM OF GOLD DEPOSITS IN METAMORPHIC ROCK PROVINCE

变质岩区金矿成矿系统的概念，系指产于中、深变质岩中或与变质岩有成因联系的金矿床组合。形成变质岩区金矿成矿系统的核心是原始含金建造。中国主要变质岩分布区，如胶东、秦岭、乌拉山、大青山、燕山、辽东，都有含金建造存在，含金丰度５×１０－９～６００×１０－９，高于地壳或上地幔的平均克拉克值（４×１０－９～５×１０－９）。目前这些地区已发现了一系列金矿，其金矿成矿物质来源于含金建造。变质富集作用包括区域高温高压变质作用、混合岩化作用、构造剪切作用，甚至于部分熔融作用、重熔岩浆的形成作用，所有这些地质活动可以导致含金建造中金矿物质的富集或贫化再分配。这一过程中碱性组分的溶出与再交代对金的活化带出与再沉淀成矿起到重要作用。金矿化总是与钾化、硅化交代或碱性花岗岩共生。成矿变质流体中Ｋ＋，ＳｉＯ２含量较高，ｘ（Ｎａ＋）／ｘ（Ｋ＋）值接近１，进一步表明碱性组分，尤其是钾碱组分在金矿形成中是非常重要的。由于金元素的化学稳定性，在表生条件下，原生金矿的风化、破坏与再生富集是同时进行的，追踪整个的演化过程。

The definition of metallogenic system of gold deposits i n metamorphic rock province is firstly given in this paper.These gold deposits are all formed in or related to metamorphic rock. The key factor to form metallogenic system of gold deposits in metamorphic rock provinces is gold bearing formation.There are many gold bearing greenstone formation in metamorphic rock province of China,such as the eastern Shandong,Wulashan mountain,Daqingshan mountain and Yanshan mountain in North China,Qinling mountain in the centric China and the eastern Liaoning. Their gold abundance is about 5×10 -9 ～600×10 -9 ,somewhat higher than that of earth crust and mantle(4×10 -9 ～5×10 -9 ).A series of gold deposits are discovered in the metamorphic rock provinces,their gold elements are originated from gold bearing formation.Metamorphism,including regional metamorphism,migmatization,structural shearing,partial melting and the formation of remelting magma,may result in the gold elements of gold bearing formation to be redistributed, such as to be enriched and impoverished.Exsolution and metasomatism of alkaline component plays a positive role in activation,leaching and precipitating,mineralization of gold during metamorphic process.Therefore gold metallization is accompanied with potassic alteration,silication and alkali granite.The higher contents of K + and SiO 2 ,the value of x (Na +)/ x (K +) being about 1 in the metamorphic fluid show that the alkaline component,particularly the potassic component,plays an important role in the formation of gold deposits.Because the chemical properties of gold element is very stable,while the original sulphide type of gold deposit is weathered and destroyed,detrital minerals are redeposited,enriched and then formed the alluvial gold placer by supergenesis.Through the tracing of the whole process of gold evolution,a model of metallogenic system can be established for the gold deposits in metamorphic rock province.