甘肃李坝金矿床地质特征及成因研究  

GEOLOGICAL CHARACTERISTICS AND GENESIS OF THE LIBA GOLD DEPOSIT, GANSU PROVINCE

作　　者：黄杰[1] 王建业[1] 韦龙明[1] 

机构地区：[1]中国有色金属工业总公司矿产地质研究院

出　　处：《矿床地质》2000年第2期105-115,共11页Mineral Deposits

基　　金：科研项目!"秦岭地区卡林型金矿床成矿条件及成矿预测研究"

摘　　要：李坝金矿床位于中川印支 -燕山期复式花岗岩体外热变质带即黑云母变质带中 ,带内分布有较多的同类型金矿床 (点 ) ,是礼岷金矿带东部最大的金矿床。矿体产出严格受断裂破碎带控制 ,矿体主要为脉状、透镜状 ,分支复合 ,膨大缩小明显。容矿岩石主要为粉砂质板岩 ,矿石类型简单 ,主要为块状、碎裂状少硫化物浸染型 ,次为角砾状硫化物浸染型 ,矿化组合为金银系列矿物 -黄铁矿 - (毒砂 )。金矿化富集与中酸性岩脉空间密切伴生 ,同位产出。成矿作用可划分为两期四阶段 ,成矿物理化学环境为浅成中低温偏酸性还原富硫环境 (1～ 2 km、t为 188～ 2 56℃、p H为 3.6～ 5.6、lg f O2 为 - 38.8～ - 4 1、lg f S2 为 - 14.8～ - 16 )。地质、同位素地球化学综合研究认为矿床成因为岩浆 -变质混合成矿流体浅成中低温充填 -交代矿床。The Liba gold deposit lies in the exo\|thermometamorphic zone (biotite metamorphic zone) of Zhongchuan Indosinian\|Yanshanian complex granite body within Limin magmatic area in the eastern part of West Qinling Hercynian folded belt. Inside the exo\|thermometamorphic zone there exist quite a number of gold deposits (ore spots) of the same type, and the Liba deposit is the largest gold deposit in the eastern part of the Limin gold ore belt. The deposit occurs in fine clastic\|agrillaceous rocks of Middle Devonian Shujiaba Formation which suffered epimetamorphism, and the host rocks are dominated by silty slate together with a small number of quartz diorite dikes. Controlled strictly by fractured zones, orebodies are mainly in veinlike and lenticular forms with obvious phenomena of branching, compounding, expansion and contraction. Ores seem rather simple, belonging mainly to massive and cataclastic sulfide dissemination types and subordinately to brecciated sulfide dissemination type. The mineralization association comprises minerals of gold\|silver series\|pyrite\|(arsenopyrite). The ore\|forming process might be divided into two phases consisting of four stages, and the ore\|forming physicochemical environment is a shallow\|seated mesothermal\|epithermal acid reduced sulfur\|rich environment (1～2 km, t =188～256℃, pH=3 6～5 0,lg f O 2 =-38 8～-41,lg f S 2 =-14 8～-16 0). The Rb\|Sr isochron age of inclusions in pyrite, the main gold\|bearing mineral, is 172×10 6a, and the initial ratio is 0 715, suggesting that it was formed simultaneously with the magmatic intrusion of Zhongchuan rock body. Geological and isotopic geochemical integrated studies show that the ore deposit is genetically a shallow\|seated mesothermal\|epithermal filling\|metasomatic deposit formed by magmatic\|metamorphic mixed ore\|forming fluids.

关 键 词：金矿床 地质特征 成矿 物理化学条件 矿床成因 

分 类 号：P618.510.2[天文地球—矿床学] P618.510.1[天文地球—地质学]