Form of Gold and its Relation to the Hydrothermal History of Carlin-type Deposits

凯斯勒等人要求提供资金，对金的形态及其与卡林型矿床热液历史的关系进行全面研究。对这些矿床的研究大多集中在宏观(地质)观察上，对微观特征关注较少。它们留下了一幅关于卡林型矿床中黄金的形式以及它与矿床的起源和年龄之间的关系的零散图景。这项研究将结合最先进的高分辨率透射电子显微镜(HRTEM)和X射线吸收近边缘结构(XANES)与更传统的表面离子质谱仪(SIMS)分析，以提供全面的矿物学信息。工作将集中在双溪、Betze-Post-Screamer和Meikle Carlin类型的矿床上，所有这些类型的矿床都已进行了很好的地质学研究。通过结合从原子尺度到矿床尺度的观察，我们将更好地控制金在这些矿床中的迁移和沉积机制，以及它们的热液历史和年龄。我们的主要目标将是确定这些矿床中金的主要寄主--砷黄铁矿中的构造结合金是否以毒砂/黄铁矿夹层的形式存在，以及它们与在这些矿床的勘察研究中观察到的纳米级金颗粒之间的关系。这一信息很重要，因为受结构约束的黄金可能是从相对于自然金未饱和的溶液中沉积出来的，从而使它们在形成过程中能够更有效地收集黄金。我们还将评估含砷黄铁矿的金矿和小颗粒自然金是同时代的，还是在不同的时间沉积的。需要这些信息来将金与适当的矿化阶段联系起来，并评估内华达州卡林型矿床是由几个空间重叠的金矿沉积事件形成的可能性。来自非饱和溶液的沉积和多次事件的形成也有助于解释为什么这些沉积物如此之大。最后，我们的工作将把矿床与它们的地质和构造环境联系起来，这对于为下一代服务的矿石勘探是必不可少的。

Kesler et al 0207273This proposal requests funding for a comprehensive study of the form of gold and its relation to the hydrothermal history of Carlin-type deposits. Most studies of these deposits have focused on macro-scale (geologic) observations with limited attention to micro-scale features. They have left a fragmented picture of the form of gold in Carlin-type deposits and how it relates to the origin and age of the deposits. The study will combine state-of-the-art high-resolution, transmission electron microscopy (HRTEM) and xray absorption, near edge structure (XANES) with more traditional surface ion mass spectrometry (SIMS) analyses to provide comprehensive mineralogical information. Work will focus on the Twin Creeks, Betze-Post-Screamer, and Meikle Carlin-type deposits, all of which have been well studied geologically. By combining observations from the atomic scale to the deposit scale, we will provide better control on mechanisms of gold transport and deposition in these deposits and on their hydrothermal history and age. Our main objectives will be to determine whether structurally bound gold in arsenian pyrite, the main host for gold in these deposits, is present as interlayers of arsenopyrite/marcasite in pyrite, and how they relate to nano-scale gold particles observed in reconnaissance studies of these deposits. This information is important because structurally bound gold might have been deposited from solutions that were not saturated with respect to native gold, thus allowing them to collect gold more efficiently during their formation. We will also evaluate whether arsenian pyrite-hosted gold and small particles of native gold are coeval or were deposited at different times. This information is needed to relate gold to the appropriate stage of mineralization and evaluate the possibility that Carlin-type deposits in Nevada were formed by several, spatially overlapping, gold-depositing events. Deposition from unsaturated solutions and formation by multiple events could also help explain why these deposits are so large. Finally, our work will relate the deposits to their geologic and tectonic setting, which is essential to exploration for ore to serve the next generation.