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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709407
• 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.

虽然我们在了解地壳熔融和流体使贱金属和贵金属在地壳中浓缩到可开采水平的过程方面取得了重大进展，但仍有一些悬而未决的问题需要解决。此外，最近的技术进步，主要是由于需要减轻人类活动对环境的影响，产生了对一组新的“关键金属”的需求，对这类金属的浓缩过程的了解还处于起步阶段。我的研究旨在解决一些未解决的问题的基础和贵金属矿床成因和开发模式的一些关键金属，即稀土元素和伴生金属矿床的成因。在这样做的过程中，我计划为科学做出根本性的贡献，这些贡献将在基础、贵金属和关键金属矿床的勘探中得到应用。成矿流体是热液还是蒸汽是斑岩铜矿和浅成低温热液型金银矿床成矿过程中一个尚未解决的问题。我和我的学生将在我们和其他人以前的工作基础上解决这个问题。为此，我们将分析合适矿床中捕获流体的成分（使用显微测温法和LA-ICPMS），并进行旨在确定金属在蒸汽中的溶解度/形态及其在液体和蒸汽之间的分配的实验。对于许多沉积物型矿石存款类型来说，一个特别令人感兴趣但却被忽视的问题是，液态碳氢化合物是否参与了金属的迁移。最近，我们已经表明，这是在南非威特沃特斯兰德金铀矿床的铀，在那里它发生在焦沥青和絮凝形成更大的聚集体，其中一些以前被误解为碎屑颗粒的晶质铀矿纳米粒子的情况。我们将通过使用LA-ICPMS和高分辨率TEM技术对MVT铅锌矿床中的碳氢化合物进行分析和成像，并通过进行旨在确定原油中金属溶解度和形态的实验来扩展这项研究。最后，我们建议文件的性质的选择稀土元素（在某些情况下与铌和锆）矿床在侵入（碳酸盐岩，霞石正长岩和花岗岩）和非侵入主机使用领域的关系，光学和SEM岩相学，矿物/岩石地球化学，流体/熔体包裹体研究），并调查金属浓缩和分馏过程。这些研究将通过热液流体中REE和Nb物种稳定性的实验研究来补充。拟议的研究有可能大大促进对各种基础，贵金属和关键金属矿床形成的理解，并帮助指导加拿大和国外对这些矿床的勘探。它还将帮助培训新一代地质学家，从事采矿业，政府和学术界的职业。