内蒙古毕力赫与侵入体有关的大型金矿床地质特征及成因研究

Geological Characteristics and Genesis of Intrusion-related Bilihe Large Gold Deposit,Inner Mongolia

内蒙古毕力赫金矿位于华北板块北缘古生代增生带内，是我国北方重要的锡、钼成矿区。与成矿有关的侵入体呈隐伏状态侵入于火山岩系中，岩性为花岗闪长（斑）岩（272～269Ma），是主要成矿岩体，形成于华北板块北缘晚古生代活动大陆边缘的增生—碰撞过渡环境。矿床主矿体以隐伏状态产于花岗闪长（斑）岩体及其接触带，从岩体中心向外金品位逐渐变贫。矿石类型主要为矿化的花岗闪长斑岩，岩石内发育大量席状含金石英脉、网状脉及接触带部位的单向固结结构（UST），与金品位呈正相关。围岩蚀变以岩体内的钾化和硅化为主，其次为高岭土化，以及外围大面积的伊利石化、青磐岩化等。矿石石英中流体为含CO2的水溶液，原生包裹体均一温度划分为2个峰值区（430—550℃和〈380℃），研究表明，成矿流体早期主要来源于岩浆，随着成矿空间的抬升和成矿过程的延续，有不同程度的大气降水加入。成矿年代学研究表明，花岗闪长斑岩体内辉钼矿Re-Os等时线年龄为（272．7±1．6）Ma，成矿作用开始于花岗闪长岩岩浆结晶晚期。对比表明，毕力赫金矿床与跨越欧亚大陆的全球性与侵入体有关的金矿床成矿带的许多矿床特征相似，是我国同类型金矿床的典型代表。

Bilihe gold deposit in Inner Mongolia is located in the northern margin of the North China Craton Paleozoic accretionary zone,which is important area of Sn-Mo mineralazation area in the northern China.Intrusion related to mineralization intruded into the volcanic rocks, is the main ore-forming rock formed in the northern margin of the late Paleozoic active continental North China Craton＇s edge of accretionary-collisions transition setting, composed of granodiorite （porphyry） rock（272 to 269 Ma）.The main ore bodies as consealed state lie in the granodiorite rock body and the contact zone between the granodiorite and wall rock.Ore grade from the terrane＇scenter to its outer gradually depleted.Ores mainly make up of granodiorite porphyry with a large number of sheeted auriferous quartz veins,stockworks and the typical unidirectional solidifition texture （UST） in contact,and a positive correlation with the gold grade.Metal sulphide content of the ore is very low （less than 2% ）.Alterations are first potassium and silicifiedand second kaolin in the intrusion,and widely illitization propylitization outer.Geochemical Character of Au ＋Bi yTe ＋-W ＋As ＋Sn ＋Cu ＋W ＋-Mo is similar to the intrusion-related gold deposits. Ore-bearing quartz fluid is an aqueous solution containing CO2,with the native homogenization temperature of 430-550 ℃ and less than 380 ℃ and salinity of 0.88%-8.68% NaCI and 12.5%-17.5% NaCl.The study showed that the early ore- forming fluids come from the magma, and have varying degrees of precipitation with the uplift of the mineralization space and the mineralization process.Geochronology studies have shown that the molybdenite Re-Os isochron age of the granodioritic porphyry is 272.7±1.6 Ma,mineralization began in the late of the granodiorite magma.Deposit characteristics show that Bilihe gold deposit conforms to the across Eurasia global intrusion-related gold mineralization,and is a typical representative of the same type gold deposits in China.