Invisible gold in arsenian pyrite and arsenopyrite from a multistage Archaean gold deposit: Sunrise Dam, Eastern Goldfields Province, Western Australia
Invisible gold in arsenian pyrite and arsenopyrite from a multistage Archaean gold deposit: Sunrise Dam, Eastern Goldfields Province, Western Australia
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DOI：
10.1007/s00126-009-0244-4
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发表时间：
2009-06
影响因子：
4.8
通讯作者：
Y. Sung;J. Brugger;C. Ciobanu;A. Pring;W. Skinner;M. Nugus
中科院分区：
文献类型：
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作者：
Y. Sung;J. Brugger;C. Ciobanu;A. Pring;W. Skinner;M. Nugus
日出Dam金矿（11.1 Moz Au）是西澳大利亚州Laverton绿岩带（东金矿省，Yilgarn Bethon）最大的存款。该存款的特点是多个事件的流体流动，导致重复蚀变和矿化旁边的一个主要的地壳规模的结构。采用原位激光烧蚀电感耦合等离子体质谱法（LIMS）对不同构造和岩石地层环境下的4个成矿阶段（D1、D3、D4 a和D4 b）的砷黄铁矿和毒砂中的Au含量进行了测定。黄铁矿含有高达3，067 ppm的Au（n= 224），而毒砂含有高达5，767 ppm（n= 19）。金在毒砂（D4 a阶段）共沉淀，并保持为“看不见的金”（纳米粒子和/或晶格结合）在随后的变形事件。相反，黄铁矿中的金不仅以“看不见的金”的形式存在，而且还以自然金、银金矿和Au（Ag）-碲化物的微米级包裹体的形式存在。原始D1和D3砷黄铁矿中Au含量较低（≤26 ppm）。最高的Au浓度发生在D3黄铁矿重结晶的D4 a富砷黄铁矿中。织构分析表明，该再结晶过程是通过溶解-再沉淀耦合过程进行的，这一过程可能有助于D4 a期间Au品位的提高。而D4 b黄铁矿中的Au则表现为“看不见的”金在颗粒尺度上的再分布，形成微米尺度的Au矿物包裹体。日出坝Au的形态和省尺度存款的特殊规模是由单一管道系统内的多种流体流动和多种Au沉淀机制造成的。
The Sunrise Dam gold mine (11.1 Moz Au) is the largest deposit in the Archaean Laverton Greenstone Belt (Eastern Goldfields Province, Yilgarn Craton, Western Australia). The deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal-scale structure. The Au content of arsenian pyrite and arsenopyrite from four mineralizing stages (D1, D3, D4a, and D4b) and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry. Pyrite contains up to 3,067 ppm Au (n= 224), whereas arsenopyrite contains up to 5,767 ppm (n= 19). Gold in arsenopyrite (D4astage) was coprecipitated and remained as “invisible gold” (nanoparticles and/or lattice-bound) during subsequent deformation events. In contrast, gold in pyrite is present not only as “invisible gold” but also as micrometer-size inclusions of native gold, electrum, and Au(Ag)–tellurides. Pristine D1and D3arsenian pyrite contains relatively low Au concentrations (≤26 ppm). The highest Au concentrations occur in D4aarsenian-rich pyrite that has recrystallized from D3pyrite. Textures show that this recrystallization proceeded via acoupleddissolution–reprecipitation process, and this process may have contributed to upgrading Au grades during D4a. In contrast, Au in D4bpyrite shows grain-scale redistribution of “invisible” gold resulting in the formation of micrometer-scale inclusions of Au minerals. The speciation of Au at Sunrise Dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple Au-precipitating mechanisms within a single plumbing system.