上黑龙江盆地砂宝斯金矿黄铁矿地球化学特征及其成矿意义
投稿时间:2023-10-14  修订日期:2023-12-03  点此下载全文
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作者单位邮编
王远超 中国地质调查局军民融合地质调查中心 610036
谭伟 中国地质大学地球科学与资源学院 
赵元艺* 中国地质科学院矿产资源研究所 
刘金龙 中国地质调查局军民融合地质调查中心 
何理 中国地质调查局军民融合地质调查中心 
陈行 中国地质调查局军民融合地质调查中心 
黄军海 中国地质调查局军民融合地质调查中心 
巩鑫 贵州省有色金属和核工业地质勘查局地质矿产勘查院 
中文摘要:内容提要:砂宝斯金矿床是上黑龙江盆地内唯一的大型岩金矿床,但其成矿物质来源和矿床成因仍然存在争议。为此,在详细的矿相学和黄铁矿显微结构研究基础上,对不同世代黄铁矿开展LA-ICP-MS微量元素和S、Pb同位素分析。结果表明,砂宝斯金矿床从成矿早期到主成矿阶段,黄铁矿可划分为3个世代,不同世代黄铁矿微量元素组成差异明显。PyII为金的主成矿期,其中Au、Ag、Cu、Pb、Zn、Bi、Co、Ni、As、Mn、Sb、Sn、Ga等元素含量较高。Co、Ni、As以类质同象的形式进入黄铁矿晶格,Cu、Pb、Zn、Sb、Bi元素以金属硫化物矿物包裹体的形式赋存于黄铁矿中。Au元素以Au+、银金矿、铜金矿矿物包裹体微粒和亚微米的包体金形式存在于黄铁矿中。As置换S,形成Au(HAs)-,对Au的迁移及沉淀具有重要的作用。砂宝斯金矿床黄铁矿Co/Ni比值大多数小于1,大部分点落入沉积成因范围,少部分落入火山成因和热液成因范围,表明黄铁矿并非单一来源。综合S、Pb同位素及黄铁矿微量元素特征,砂宝斯金矿床成矿物质既来源于具上地壳和地幔混源特征的深部岩浆,又来源于二十二站组围岩。结合区域成矿构造背景,认为蒙古-鄂霍茨克洋闭合后,早白垩世陆壳拆沉引发岩浆作用形成的初始成矿流体形成PyI型黄铁矿,Cu、Pb、Zn、Ag、Au、Bi含量较少,Co、Ni含量相对较高;由于大气降水的加入,成矿流体运移过程中萃取二十二站组围岩中成矿物质,富含As,Cu,Pb,Bi,Au,Ag,形成沉积成因的PyⅡ型黄铁矿;成矿晚期由于大气降水的减少,形成既有沉积成因又有热液成因的PyⅢ型黄铁矿。砂宝斯金矿床成因类型为岩浆热液型金矿床。
中文关键词:黄铁矿  原位微量元素  硫-铅同位素  砂宝斯金矿床  上黑龙江盆地
 
Geochemical characteristics of pyrite from Shabaosi gold deposit in the Upper Heilongjiang Basin and its mineralization significance
Abstract:The Shabaosi gold deposit is the only large-scale rock gold deposit in the Upper Heilongjiang Basin, but the source of ore-forming metrials and ore genesis of this deposit remain controversial. Therefore, based on detailed ore mineralogy and pyrite microstructure analysis, LA-ICP-MS trace elements and S, Pb isotopic analysis were carried out on different generations of pyrite. The results showed that pyrite in Shabaosi gold deposit can be divided into three generations (i.e., PyI, PyII and PyIII) from early mineralization to the main mineralization stage, and different phases of pyrite have obviously different trace element compositions. PyII is the main metallogenic stage of the deposit, in which elements such as Au, Ag, Cu, Pb, Zn, Bi, Co, Ni, As, Mn, Sb, Sn, and Ga had relatively high contents. Co, Ni, and As in the three generations of pyrite occur as homo-isomorphs form in the overall pyrite. Cu, Pb, Zn, Sb, Bi elements occur in Pyrite in the form of metallic Sulfide mineral inclusions. Au occurs as Au+, silver-gold, copper-gold mineral particles and submicron-sized Au particles in pyrite. As replaces S to form Au(HAs)-, which plays an important role in the migration and precipitation of Au. The majority of Co/Ni ratio is less than 1, most of which fall within the category of sedimentary area. While some points of PyI and PyⅢ type Pyrite Co/Ni fall into hydrothermal area and volcanic area. These indicate that Pyrites from the deposit is not a single source. Combining the S and Pb isotopic characteristics and trace elements of pyrite, the source of ore-forming materials of the deposit was derived from deep magma source with a mixture of upper crust and mantle characteristics and the surrounding strata Ershierzhan Formation. Combined with the regional metallogenic background, it is believed that the initial ore-forming fluids formed by Early Cretaceous magmatism formed PyI type Pyrite. And the Early Cretaceous magmatism was triggered by the continental crust delamination after the closure of the Mongolia Okhotsk Ocean. The content of Cu, Pb, Zn, Ag, Au and Bi from PyI type Pyrite is relatively low, and the content of Co and Ni is relatively high. Due to the addition of meteoric water, the ore-forming fluids extracted the ore-forming material in the Ershierzhan Formation, rich in As, Cu, Pb, Bi, Au, Ag, forming the sedimentary PyII type Pyrite. PyⅢ type Pyrite of both sedimentary and hydrothermal origin was formed due to the reduction of meteoric water in the late stage of mineralization. Therefore, the Shabaosi gold deposit is considered to be a magmatic hydrothermal gold deposit.
keywords:Pyrite  In situ trace elements  S-Pb isotopes  Shabaosi gold deposit  Upper Heilongjiang Basin
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