The Fortitude Gold Skarn Deposit

金夕卡岩的黄金总产量/储量约为美国矿山年产量的四倍，是多个大陆主要勘探项目的重点，但人们对它们的地质、矿物学、地球化学或岩石成因知之甚少。拟议的研究将记录世界上最大、最具经济意义的金夕卡岩的地层背景、岩石学、矿物学、流体包裹体特征、微量元素地球化学和稳定同位素特征。这项研究的基本方法将是详细的地质填图。富含碎屑、碳质和碳酸盐的层序的重要性可能在热液系统的演化中起着关键作用，缓冲了随后的钙硅酸盐和硫化物矿物组合。这些还原条件反映在以铁为主的钙硅酸盐组合和还原的硫化物物种上。初步工作表明，与大多数其他类型的夕卡岩相比，来自许多含金夕卡岩系统的辉石往往更富铁(直至纯辉长花岗岩)，角闪石和石榴石最终更富铝。本研究的目的之一是建立坚韧金夕卡岩矿床演化的成因模式，特别是回答什么是金夕卡岩的问题。“一个人是如何形成的？”以及“他们的发现可以用什么勘探标准？”目前，这些重要的科学和经济问题无法得到回答。这项提案中概述的研究旨在使用最重要和最受欢迎的系统来寻找答案。

Gold skarns have total gold production/reserves about four times greater than U.S. annual mine production and are the focus of major exploration programs on several continents, yet little is known about their geology, mineralogy, geochemistry, or petrogenesis. The proposed research will document the stratigraphic setting, petrology, mineralogy, fluid inclusion characteristics, trace element geochemistry, and stable isotope signature of the largest and most economically important gold skarn in the world. The basic approach for the study will be detailed geologic mapping. The importance of a clastic rich, carbonaceous, carbonate sequence may play a key role in the evolution of the hydrothermal system, buffering subsequent calc-silicate and sulfide mineral assemblages. These reducing conditions are reflected in the ferrous iron dominant calc-silicate assemblages and reduced sulfide species. Preliminary work indicates that pyroxenes from many gold-bearing skarn systems tend to be more iron-rich (up to pure hedenbergite) and amphiboles and garnets t end to be more aluminum-rich, than most other skarn types. One of the goals of this study is to establish a genetic model for the evolution of the Fortitude gold skarn deposit; in particular, to answer the questions, "What is a gold skarn?" "How does one form?", and "What exploration criteria can be used for their discovery?" At present these important scientific and economic questions cannot be answered. The research outlined in this proposal is designed to find the answers using the most important and well exposed system.