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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=668620
• 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.

尽管我们在了解地壳熔体和流体将贱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实质性进展，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为了减轻人类活动对环境的影响，从而产生了对一组新的“关键金属”的需求，而对这些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尚未解决的贱金属和贵金属矿石成因问题，并开发一些关键金属（即稀土金属和伴生金属）矿床成因的模型。在此过程中，我计划为科学做出根本性贡献，并将其应用于贱金属、贵金属和关键金属矿床的勘探。斑岩铜矿和浅成热液金银矿形成的一个未解决的问题是矿石流体是热液还是蒸气。我和我的学生将通过我们自己和其他人之前的工作来解决这个问题。为此，我们将分析合适矿床中截留流体的成分（使用显微测温法和 LA-ICPMS），并进行旨在确定金属在蒸气中的溶解度/形态及其在液体和蒸气之间的分配的实验。对于许多沉积物矿床类型来说，一个特别有趣且基本上被忽视的问题是液态碳氢化合物是否可能参与金属运输。最近，我们发现南非威特沃特斯兰德金铀矿床中的铀就是这种情况，它以焦沥青中的铀矿纳米粒子的形式出现，并絮凝形成更大的聚集体，其中一些聚集体以前被误解为碎屑颗粒。我们将使用 LA-ICPMS 和高分辨率 TEM 技术对 MVT Pb-Zn 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的溶解度和形态的实验，从而扩大这项研究。最后，我们建议利用现场关系、光学和扫描电镜岩相学、矿物/岩石地球化学和流体/熔体包裹体研究，记录侵入体（碳酸岩、霞石正长岩和花岗岩）和非侵入体中精选稀土元素（在某些情况下与铌和锆相关）矿床的性质，并研究金属富集和分馏过程。这些研究将得到热液中 REE 和 Nb 物质稳定性的实验研究的补充。拟议的研究有可能显着增进对各种贱金属、贵金属和关键金属矿床形成方式的了解，并有助于指导加拿大和国外对这些矿床的勘探。它还将有助于培训新一代地质学家在采矿业、政府和学术界的职业生涯。