The Fosterville gold (Au) deposit is hosted in the Bendigo zone within the western Lachlan orogen, southeast Australia, and contains three distinct mineralization styles: (1) refractory Au in fine-grained arsenopyrite and arsenian pyrite disseminated throughout metasedimentary rocks near brittle faults, (2) visible Au hosted in fault-controlled quartz-carbonate veins associated with stibnite mineralization, and (3) vein-hosted visible Au with little or no associated stibnite. Refractory Au mineralization is found throughout the deposit, whereas visible Au ± stibnite occurs deeper in the system (>800-m depth from surface). Thus, Fosterville provides a unique opportunity to study a telescoped orogenic Au system that changes mineralization style as a function of depth. Microscopy, neutron tomography, nanoscale secondary ion mass spectrometry, and field observations have been conducted to investigate mineralogical and structural controls on the various styles of Au mineralization. These observations are used as the foundation for reactive mass transport geochemical modeling using HCh software. Results are considered in the context of an evolving mineral system over the formation history of the deposit, and relative timing of mineralization is inferred. Two alternatives for the genesis of such a system include the following: (1) metal deposition was controlled by ongoing physicochemical changes at a very shallow level in the crust in one evolving mineralization stage or (2) two or three deposits formed in the same location, with each different style of mineralization representing a separate period of fluid infiltration, each potentially tens of millions of years apart. Based on careful observations, microanalysis, and thermodynamic modeling, we suggest that the latter is more likely. Therefore, we suggest that Fosterville is to be recognized as a telescoped orogenic Au system, where relatively high temperature mineralization and alteration assemblages were overprinted vertically by later, lower-temperature assemblages.

中文翻译：

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望远镜式造山金系统的分析：福斯特维尔矿床的见解

Fosterville金（Au）矿床位于澳大利亚东南部Lachlan造山带西部的Bendigo带，并具有三种不同的矿化方式：（1）细粒砷黄铁矿和砷黄铁矿中的难熔金散布在脆性断层附近的全沉积岩中， （2）可见金存在于与辉锑矿成矿有关的断层控制的石英碳酸盐岩中，（3）可见可见金的几乎没有或没有缔合辉石的金。在整个矿床中都发现了难熔的金矿化，而可见的金±辉石矿出现在系统的更深处（距地表深度> 800 m）。因此，福斯特维尔提供了一个独特的机会来研究可伸缩的造山金系统，该系统会根据深度改变矿化方式。显微镜，中子断层扫描，纳米级二次离子质谱法，已经进行了野外观察，以研究各种样式的金矿化的矿物学和结构控制。这些观察结果用作使用HCh软件进行反应性传质地球化学建模的基础。在矿床形成过程中不断演化的矿物系统的背景下考虑结果，并推断出矿化的相对时机。该系统的成因的两个备选方案包括：（1）在一个不断发展的矿化阶段中，地壳中非常浅的水平通过持续的物理化学变化控制金属沉积，或者（2）在同一位置形成两个或三个沉积物，每种不同的矿化方式代表着一个单独的流体渗透期，每个潜在的间隔期达数千万年。根据仔细的观察，微观分析和热力学模型，我们建议后者更有可能。因此，我们建议将Fosterville视为一种望远镜造山金系统，在该系统中，相对较高的矿化度和蚀变组合在以后的低温组合中被垂直套印。