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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=692394
• 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将碱金属和贵金属浓缩到地壳中可开采水平的过程方面取得了重大进展，但仍有许多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，造成了对一组新的“关键金属”的需求，对这些金属的浓缩过程的了解还处于初级阶段。我的研究旨在解决一些尚未解决的贱金属和贵金属矿石成因问题，并建立一些关键金属矿床的成因模型，即REE和伴生金属。在此过程中，我计划为科学做出根本性的贡献，这些贡献将在基础金属、贵重金属和关键金属矿床的勘探中得到应用。斑岩型铜矿和浅成热液型金银矿的成矿流体是热液还是蒸汽是一个尚未解决的问题。我和我的学生将在我们和其他人之前的工作的基础上解决这个问题。为此，我们将分析合适矿床中被困流体的成分（使用显微测温仪和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。对于许多沉积物为主的矿床类型来说，一个特别有趣而又被忽视的问题是，液态碳氢化合物是否可能参与了金属的运输。最近，我们证明了南非Witwatersrand Au-U矿床中的铀就是这种情况，在那里，它以铀精矿纳米颗粒的形式存在于焦沥青中，并絮凝形成更大的聚集体，其中一些以前被误解为碎屑颗粒。我们将利用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，并进行旨在确定原油中金属溶解度和形态的实验，从而扩大这项研究。最后，我们建议通过野外关系、光学和扫描电镜岩石学、矿物/岩石地球化学和流体/熔体包裹体研究，记录侵入性（碳酸盐岩、霞石正长岩和花岗岩）和非侵入性寄主中REE（在某些情况下与Nb和Zr有关）矿床的性质，并研究金属的富集和分选过程。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加以补充。拟议的研究有可能显著推进对各种基础、珍贵和关键金属矿床形成方式的理解，并有助于指导加拿大和国外这些矿床的勘探。它还将帮助培养新一代的地质学家，为采矿业、政府和学术界工作。