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

Kesler等[207273]该提案要求资助对卡林型矿床的金形态及其与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）观测上，对微观特征的关注有限。他们留下了卡林型矿床中黄金形态的碎片图，以及它与矿床起源和年龄的关系。该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）以及更传统的表面离子质谱（SIMS）分析，以提供全面的矿物学信息。工作将集中在Twin creek， Betze-Post-Screamer和Meikle carlin型矿床上，所有这些矿床在地质学上都得到了很好的研究。将原子尺度与矿床尺度相结合，可以更好地控制金矿床中金的输运和沉积机制以及热液历史和年龄。我们的主要目标将是确定砷黄铁矿（这些矿床中金的主要寄主）中的结构结合金是否作为黄铁矿中毒砂/黄铁矿的夹层存在，以及它们与这些矿床侦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，因为结构结合的金可能是从相对于天然金不饱和的溶液中沉积下来的，从而使它们在形成过程中更有效地收集金。我们还将评估含砷黄铁矿的金和原生金的小颗粒是同时期还是不同时期沉积的。需要这些信息将金与适当的成矿阶段联系起来，并评估内华达州卡林型矿床是由几个空间重叠的金成矿事件形成的可能性。不饱和溶液的沉积和多种事件的形成也可以帮助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，这对于为下一代寻找矿石至关重要。

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.