Crustal melts, fluids and ore-forming processes

地壳熔化、流体和成矿过程

• 批准号: RGPIN-2016-04627
• 负责人: WilliamsJones, Anthony
• 金额: $ 6.56万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=615194
• 关键词: Crustal; melts; fluids; ore; forming

Although we have made substantial progress in understanding the processes by which crustal melts and fluids concentrate base and precious metals to exploitable levels in the Earth’s crust, there are still a number of outstanding issues to address. Moreover, recent technological advances, driven mainly by the need to mitigate the environmental impact of human activity, have created a demand for a new group of “critical metals”, for which understanding of the concentrating processes is in its infancy. My research aims to address some unresolved issues of base and precious metal ore genesis and develop models for the genesis of ore deposits of some critical metals, namely the REE and associated metals. In so doing, I plan to make fundamental contributions to science that will find application in the exploration for base, precious and critical metal deposits. An unresolved question for porphyry copper and epithermal gold-silver ore formation is whether the ore fluids are hydrothermal liquids or vapours. I and my students will address this issue by building on previous work by ourselves and others. To do so, we will analyse the compositions of the trapped fluids in suitable ore deposits (using microthermometry and LA-ICPMS) and conduct experiments designed to determine the solubility/speciation of the metals in vapour and their partitioning between liquid and vapour. A particularly interesting and largely ignored question for a number of sediment-hosted ore deposit types is whether liquid hydrocarbons could have been involved in metal transport. Recently, we have shown that this was the case for uranium in the Witwatersrand Au-U deposits, South Africa, where it occurs as uraninite nanoparticles in pyrobitumen and flocculated to form larger aggregates some of which have been previously misinterpreted as detrital grains. We will expand this research by analysing and imaging the hydrocarbons in MVT Pb-Zn deposits using LA-ICPMS and high resolution TEM techniques, and by conducting experiments designed to determine the solubility and speciation of metals in crude oil. Finally, we propose to document the nature of a selection of REE (associated in some cases with Nb and Zr) deposits in intrusive (carbonatite, nepheline syenite and granite) and non-intrusive hosts using field relationships, optical and SEM petrography, mineral/rock geochemistry, and fluid/melt inclusion studies), and investigate the metal concentrating and fractionating processes. These studies will be complemented by experimental studies of the stability of REE and Nb species in hydrothermal fluids. The proposed research has the potential to significantly advance understanding of how a variety of base, precious and critical metal deposits form, and help guide exploration for these deposits in Canada and abroad. It will also help train a new generation of geologists for careers in the mining industry, government and academia.

尽管我们在理解地壳和液体浓度基础和贵金属到地球上可探索水平的过程中取得了重大进展，但仍有许多出色的问题需要解决。此外，最近的技术进步主要是由于减轻人类活动的环境影响的必要性而驱动的，这对新的“关键金属”的需求提出了需求，这是对集中过程的理解。我的研究旨在解决一些未解决的基础和珍贵金属矿石起源的问题，并为某些关键金属的矿石沉积物的起源（即REE和相关金属）开发模型。在这样做的过程中，我计划为科学做出基本贡献，以在探索基础，珍贵和关键的金属矿床的探索中找到应用。关于斑岩铜和表皮金丝矿石的一个未解决的问题是矿石是水热液体还是蒸气。我和我的学生将通过我们和他人以前的工作来解决这个问题。为此，我们将分析合适的矿石沉积物中捕获的液体的组成（使用微热计和LA-ICPMS），并进行旨在确定蒸气中金属的溶液/特殊的实验，并在液体和蒸气之间进行分配。对于许多沉积物托管的矿床类型，一个特别有趣且在很大程度上被忽略的问题是液态碳氢化合物是否可以参与金属运输。最近，我们已经表明，南非的Witwatersrand au-u沉积物中的铀就是这种情况，在那里它以毒bi素中的铀矿纳米颗粒的形式出现，并被絮凝以形成较大的聚集体以前一些以前曾被误解为碎屑。我们将通过分析和成像使用LA-ICPM和高分辨率TEM技术的MVT PB-ZN沉积物中的烃扩展这项研究，并通过进行旨在确定原油中金属的溶液和规格的实验。最后，我们建议使用现场关系，光学和SEM岩岩，矿物质/岩石地球化学和流体/融合量研究和金属浓度和金属浓缩过程，并研究了侵入性（碳酸盐，宁片蓝石和花岗岩）中选择REE的性质（在某些情况下与NB和ZR相关）以及非侵蚀性宿主。这些研究将通过对水热液中REE和NB物种的稳定性的实验研究来完成。拟议的研究有可能大大提高人们如何形成各种基础，珍贵和关键的金属沉积物，并帮助指导加拿大和国外的这些沉积物的探索。它还将帮助培训新一代地质学家在采矿业，政府和学术界的职业。