青海省祁漫塔格牛苦头铅锌矿床氧逸度特征与铅锌成矿作用关系研究  

The Relationship Between Oxygen Fugacity and Pb-Zn Mineralization in the Niukutou Pb-Zn Deposit of the Qimantag Area,Qinghai Province

作　　者：程会 程旭 王新雨 CHENG Hui;CHENG Xu;WANG Xinyu(Henan Yudi Science and Technology Group Co.,Ltd,Zhengzhou,Henan 450008;Henan Institute of Geological SciencesCo.Ltd.,Zhengzhou,Henan 450001;Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012)

机构地区：[1]河南省豫地科技集团有限公司,河南郑州450008 [2]河南省地质科学研究所有限公司,河南郑州450001 [3]北京矿产地质研究院有限责任公司,北京100012

出　　处：《地质与勘探》2024年第5期863-881,共19页Geology and Exploration

基　　金：中国铜业重点科技项目“青海省格尔木牛苦头及外围铅锌成矿规律研究与潜力评价”(编号:QHHX-KZ-JF2020-001)资助。

摘　　要：牛苦头矿床位于青海柴达木盆地西南缘、祁漫塔格成矿带中部,属于典型的矽卡岩型铅锌多金属矿床。根据与成矿作用的关系,将牛苦头矿床早-中泥盆世岩浆岩分为成矿岩体与非成矿岩体。为查明该两种岩体的地球化学性质差异,以及岩体氧逸度特征与铅锌成矿作用关系,本文对牛苦头矿床成矿岩体与非成矿岩体开展锆石微量元素和黑云母电子探针分析。结果显示成矿岩体两个样品锆石Ce^(4+)/Ce^(3+)比值区间分别为9.94~227.72(平均值为27.24)、9.79~197.95(平均值为34.13),非成矿岩体两个样品锆石Ce^(4+)/Ce^(3+)比值区间分别为10.08~39.13(平均值25.41)、8.14~33.78(平均值19.16)。成矿岩体锆石Ce/Nd均值分别为8.42和9.87,而非成矿岩体样品锆石Ce/Nd均值分别为8.20和2.69。根据锆石Ti含量计算的锆石结晶温度,成矿岩体锆石结晶温度(平均值分别为700℃和696℃)略高于非成矿岩体(平均值分别为685℃和682℃)。据此推算的锆石绝对氧逸度显示,成矿岩体平均值分别为-17.57和-14.99,略高于非成矿岩体,后者绝对氧逸度平均值分别为-17.76和-22.49。另外,通过黑云母电子探针分析结果推算,成矿岩体的氧逸度、挥发分含量也略高于非成矿岩体。因此,本文认为成矿岩体氧逸度的升高可能更有利于矽卡岩型铅锌矿床的形成。通过与前人资料分析对比,矽卡岩型铅锌矿床成矿岩体的锆石氧逸度明显低于矽卡岩型-斑岩型铜钼矿,而与矽卡岩型钨锡矿相关的花岗岩锆石氧逸度相似。由此认为成矿岩体氧逸度高低对于成矿类型(铜钼、铅锌、钨锡)有显著的限制作用,岩体锆石氧逸度高低可能与地质背景以及源区幔源成分贡献比例有关。The Niukutou deposit is located in the southwestern margin of the Qaidam Basin and the central part of the Qimantag metallogenic belt,Qinghai Province,which is a typical skarn Pb-Zn polymetallic deposit.According to the relationship with mineralization,the Early-Middle Devonian magmatic rocks in this deposit are divided into ore-forming rock mass and non-ore-forming rock mass.This work aims to investigate the differences of geochemical characteristics between ore-forming and non-ore-forming rock masses,as well as the relationship between oxygen fugacity and Pb-Zn mineralization.Trace elements analysis of zircons and electron probe analysis of biotite show that the Ce^(4+)/Ce^(3+)values of zircons in the two samples of the ore-forming rock mass range from 9.94 to 227.72(27.24 on average)and 9.79 to 197.95(34.13 on average),respectively.In contrast,the Ce^(4+)/Ce^(3+)values of zircons in the two samples of the non-ore-forming rock mass lie in 10.08~39.13(25.41 on average)and 8.14~33.78(19.16 on average).The average Ce/Nd values of zircons in ore-forming rock samples are 8.42 and 9.87,while those for non ore-forming rock samples are 8.20 and 2.69.According to the calculated zircon crystallization temperature based on the Ti content of zircons,the zircon crystallization temperature of the oreforming rock mass(averaging 700 and 696)is slightly higher than that of the non-ore-forming rock mass(averaging 685 and 682).The absolute calculated oxygen fugacity of zircons in the ore-forming rock mass is-17.57 and-14.99,which is also larger than that of the non-ore-forming rock mass(averaging-17.76 and-22.49).In addition,electron probe analysis of biotite suggests that the oxygen fugacity and volatile content of ore-forming rock mass are higher than those of non-forming rock mass.It is thus inferred that the increase in oxygen fugacity of the ore-forming rock mass may be more conducive to the formation of Pb-Zn skarn deposits.Compared with previous data,the oxygen fugacity of rocks related to Pb-Zn mineralization is lower tha

关 键 词：铅锌矿 锆石微量元素 黑云母电子探针 氧逸度 牛苦头矿床 祁漫塔格 青海省 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学] P618.42P618.43