摘要
花牛山金矿位于北山造山带南部,矿体产出于印支期钾长花岗岩脉与大理岩的接触部位,成矿期次可划分为早期矽卡岩期和晚期石英硫化物期(主成矿期)。主成矿期中石英和方解石的流体包裹体性质表明,Ⅰ、Ⅱ阶段成矿流体均具有中低温、中盐、中高密度以及含CO_(2)和CH_(4)的特征,属H2O-CO_(2)-NaCl体系;温度—盐度特征指示成矿流体主要为岩浆水和大气降水混合来源;方解石δ^(13)CV-PDB平均值为1.7‰,δ^(18)OV-PDB平均值为-22.5‰,δ^(18)OV-SMOW平均值为7.69‰,O同位素呈强烈分异特征,暗示着成矿流体为岩浆水和大气降水混合来源。矿石中黄铁矿S同位素δ^(34)S平均值为-9.73‰,其较大的负值或与围岩地层有关,指示该矿床硫源或为岩浆与地层的混合来源。成矿深度及压力特征表明花牛山金矿属于浅成型矿床。综合分析认为,花牛山金矿床为中低温热液交代型(矽卡岩型)金矿床,可能是晚三叠世时期花牛山地区多期次的后造山岩石圈伸展和幔源岩浆底侵作用导致来自深处的成矿流体沿着裂隙断裂向上移动,与围岩发生反应并与大气降水混合,随着压力降低,成矿物质沉淀富集,随之发生金成矿作用。
The Huaniushan gold deposit is located in the south of Beishan orogenic belt.The orebody is hosted in the contact zone between the Indosinian K-feldspar granite veins and marble.The mineralization process can be divided into early skarn stage and late quartz sulfide stage(main metallogenic stage).The fluid inclusion properties of quartz and calcite in the main metallogenic period indicate that the ore-forming fluid has the characteristics of medium-low temperature,medium salt,medium-high density,and with CO_(2) and CH_(4),which belongs to the H_(2)O-CO_(2)-NaCl system.The temperature-salinity characteristics indicate that the ore-forming fluid is the mixture of magmatic water and atmospheric precipitation.The average value ofδ^(13)CV-PDB,δ^(18)OV-PDB andδ^(18)OV-SMOW of calcite is 1.7‰,-22.5‰and 7.69‰,respectively,and the O isotope strong differentiation suggest that magmatic water mixed with atmospheric precipitation to form ore-forming fluids.The average value of sulfur isotopeδ^(34)S of pyrite in the ore is-9.73‰,and its large negative value may be related to the surrounding rock strata,indicating that the sulfur source of the deposit may be a mixed source of magma and strata.The metallogenic depth and pressure features hint that the Huaniushan gold deposit belongs to the shallow metal-logenic depth.Comprehensive analysis shows that Huaniushan gold deposit is a medium-low temperature hydrothermal metasomatic(skarn type)gold deposit.Summarily,in the late Triassic,Huaniushan area expe-rienced multi-stage post-orogenic lithospheric extension and mantle-derived magma underplating,the ore-forming fluid produced in the deep and moved upward along the fracture,reacted with the surrounding rock and mixed with atmospheric precipitation.With the pressure decreasing,the ore-forming materials were precipitated and enriched,and initiated the gold mineralization.
作者
宋高瑞
翟新伟
王二腾
武磊
陈万峰
郑菲菲
王海东
王金荣
SONG Gaorui;ZHAI Xinwei;WANG Erteng;WU Lei;CHEN Wanfeng;ZHENG Feifei(WANG Haidong,WANG Jinrong School of Earth Sciences,Lanzhou University,Lanzhou 730000,Gansu,China)
出处
《黄金科学技术》
CSCD
2023年第6期873-887,共15页
Gold Science and Technology
基金
国家第二次青藏科考项目“活动断裂与地震灾害”(编号:2019QZKK0901)
中央高校基本科研业务费专项资金(编号:lzujbky-2023-it17)联合资助。
关键词
流体包裹体
成矿流体
成矿深度
岩浆底侵
矽卡岩型金矿床
花牛山金矿
fluid inclusions
ore-forming fluid
metallogenic depth
magma underplating
skarn-type gold deposit
Huaniushan gold mine
