SusChEM: Solubility of Iron Oxides and Gold in Acidic Hydrothermal Brines: Applications to the Origin of Iron Oxide Copper-gold Deposits

随着世界人口的持续增长和工业化程度的日益提高，发现新的矿藏以提供人类赖以生存的原材料的需求即使不会增加，也会保持稳定。就黄金而言，采矿业在20世纪70年代和80年代进行了数十年的积极勘探，导致全球范围内发现了经济上可开采的金矿。然而，新金矿的发现速度在过去10年里大幅下降，部分原因是该行业的低迷，部分原因是大多数接近地表、符合常规勘探模式的矿床已经被发现。该项目将调查一类新发现的热液金矿床的成因，这些矿床被称为“铁氧化物铜金”(IOCG)矿床，有可能在金属采矿业引发新的勘探和发现周期。尽管IOCG级包括世界上最大的金属矿床之一--澳大利亚的奥林匹克大坝，但对于这些矿床是如何形成的--从地质学、地球化学学、岩石学或板块构造意义上--还没有达成共识。缺乏共识的部分原因是，我们在基本的热力学层面上对铁、金和铜等金属如何在高温热液中溶解和沉淀的理解存在差距。该项目将通过在受控实验室条件下进行几组热液实验，帮助填补这一知识空白。这种类型的研究将对采矿业和整个社会产生直接好处，因为社会需要稳定的这些矿物商品的供应。至于任何产生新的高质量热力学数据的科学研究，这些结果也将有助于其他学科的科学家进一步了解塑造古代和现代地球的过程。大多数研究人员同意，形成IOCG矿床的流体是被异常氧化的高温咸水：除此之外，矿床模型存在分歧。本项目将研究氧化铁和金在100至350摄氏度的酸性氧化盐水中的溶解度，以及在铁(Fe3+)/铁(Fe2+)水溶液边界附近缓冲的氧化态下的溶解度。该项目将产生有关氯化铁、亚铁和金氯化物水溶液稳定性的新的热力学数据。这些新数据将被用来开发更准确的IOCG矿床(和其他类型的Au-Cu-Fe矿床)形成的地球化学模型。

As the world's population continues to expand and become increasingly industrialized, there will be a steady if not increasing need to discover new mineral deposits to provide the raw commodities that humans have come to depend on. In the case of gold, several decades of aggressive exploration by the mining industry in the 1970s and 1980s led to a global boom in the discovery of economically mineable gold deposits. However, the rate of discovery of new gold deposits has greatly declined in the past 10 years, partly because of a downturn in the industry, and partly because most of the deposits that are near surface and that fit conventional exploration models have already been discovered. This project will investigate the causative origins of a newly recognized class of hydrothermal gold deposits, referred to as 'iron oxide copper gold' (IOCG) deposits, that has the potential to generate a new cycle of exploration and discovery in the metal mining industry. Despite the fact that the IOCG class includes one of the largest metal deposits in the world - Olympic Dam, Australia - there is no consensus as to how - in a geologic, geochemical, petrologic, or plate tectonic sense - these deposits form. Part of the reason for this lack of consensus is a gap in our understanding at a fundamental, thermodynamic level of how metals such as iron, gold, and copper dissolve and precipitate in high temperature hydrothermal fluids. This project will help fill in this knowledge gap by performing several sets of hydrothermal experiments under controlled laboratory conditions. This type of study will have direct benefits to the mining industry and to society in general, which demands a steady supply of these mineral commodities. As for any scientific study that generates new, high-quality thermodynamic data, the results will also be useful to scientists in other disciplines to further understand the processes that have shaped the ancient and present-day Earth. Most researchers agree that the fluids that form IOCG deposits were hot, saline brines that were unusually oxidized: beyond this the ore deposit models diverge. This project will examine the solubility of iron oxide and gold in acidic, oxidized, saline brines at temperatures of 100 to 350 degrees C, and at oxidation states that are buffered near the aqueous ferric (Fe3+)/ferrous (Fe2+) boundary. The project will generate new thermodynamic data on the stability of aqueous ferric-, ferrous-, and gold-chloride complexes. The new data will be used to develop more accurate geochemical models for how IOCG deposits (and other types of Au-Cu-Fe deposits) form.