川西农都柯火山岩型低温热液Au-Ag多金属矿床的特征与成因  

Characteristics and Origin of the Nongduke Volcanic Epithermal Au-Ag Polymetallic Deposit in Western Sichuan Province

作　　者：曲晓明[1] 张绮玲[1] 侯增谦[1] 许远平 李金忠 

机构地区：[1]中国地质科学院矿产资源研究所 [2]四川省地勘局403地质队,峨嵋山614200

出　　处：《矿床地质》2001年第3期199-207,共9页Mineral Deposits

基　　金：国家"九五"科技攻关项目 (96_914_0 3_0 5 )资助

摘　　要：农都柯矿床是在义敦岛弧带中首次发现的火山岩型浅成低温Au_Ag多金属矿床。该矿床产于弧后扩张盆地的勉戈组流纹岩中 ,受韧性剪切带控制。矿床中发育一套典型的低温热液矿物组合 ,包括辉锑铅矿、辉锑银铅矿、辉锑矿、砷黝铜矿、自然金、黄铁矿、闪锌矿、雌黄、雄黄、登红石 (HgO)等。蚀变作用以硅化和绢云母化为主 ,伴生重晶石化和蒙脱石化。按照现行的火山岩型低温热液金_银矿床的分类原则 ,该矿床应属于高硫的酸性硫酸盐型。流体包裹体研究表明 ,主要成矿过程发生在 2 2 1～ 130℃之间 ;成矿流体的温度与盐度演化趋势暗示着矿床之下存在一隐伏岩浆房。硫、铅同位素显示成矿物质主要来自弧后火山岩 ,矿床是岩浆热液与大气降水对含矿火山岩 (矿源层 )The Nongduke deposit is the first volcanic epithermal Au_Ag polymetallic deposit found in the Yidun arc zone. The deposit occurs in the rhyolite area of Miange Formation within the back_arc spreading basin and is controlled by a shearing belt. There develops a typical epithermal mineral association in the deposit, which consists of zinckenite, diaphorite, antimonite, tennantite, native gold, pyrite, sphalerite, orpiment, realgar, and mercury oxide. The alterations are mainly silicification and sericitization, and, subordinately, baritization and montmorillonitization. According to the current classification of the volcanic epithermal gold_silver deposits, the Nongduke deposit should be of high_sulfur acid sulphate type. Fluid inclusion studies show that the main ore_forming process occurred in the temperature range of 130～221℃. The correlation trend between t h and salinity of the ore_forming fluids implies that a buried magma chamber might exist under the deposit. The S, Pb isotope data also indicate that the ore_forming metals were mainly derived from the back_arc volcanics. The deposit was produced by the combined interaction of magmatic fluids and meteoric water recycling through the ore_bearing volcanics.

关 键 词：义敦岛弧 火山岩 四川 弧后扩张盆地 金银多金属矿床 岩浆 成矿物质 

分 类 号：P618.51[天文地球—矿床学] P618.52[天文地球—地质学]