From arc magmas to ores (FAMOS): A mineral systems approach

社会依赖可靠的金属和矿物供应来实现经济增长、提高生活水平和发展基础设施。人口增长意味着，即使回收利用和资源效率提高了，仍需要发现新的矿藏。对新资源的有效勘探和发现需要新的概念和新的工具。矿物系统勘探方法从有利于矿床形成的“成分”、过程和环境的角度考虑岩石圈范围内的矿床。这种方法相当于一种“源-路径-陷阱”模型，更加强调预测能力，而不仅仅是特征识别。从历史上看，很多研究都集中在圈闭和矿床本身的特征上；在这里，我们的目标是通过将矿床形成与火成岩岩石学和火山学产生的岩浆作用概念结合起来，更深入地关注系统。这其中存在一个挑战，因为现有的斑岩系统模型与地壳构造和弧形火山作用的岩浆模型越来越不一致。地壳岩浆作用的新兴岩石学模型不再是从富含液体的大型岩浆室的角度来看待岩浆系统，而是转向横跨大部分或全部地壳的以晶体为主、挥发分含量高的“糊状”系统。这种系统的动力学不仅对弧岩浆作用有重要影响，而且对挥发分的化学作用也有重要影响。这些相同的挥发物促进了矿化，这是我们旨在通过召集来自经济地质学、火成岩和变质岩石学、火山学、地球化学、数值模拟和流体动力学的多学科研究团队来开发的协同效应。我们的团队涵盖了目前在英国从事斑岩矿化研究的几乎所有人，并利用了英国ROS与采矿业之间现有的牢固联系，其中许多人是项目合作伙伴。这项研究将涉及使用丰富的现代分析工具对各种矿化和贫瘠环境中的矿物进行分析，这些工具能够确定一系列广泛的微量元素和同位素示踪剂。由于不同元素对不同相(矿物、熔体和流体)的亲和力不同，每种微量元素对岩浆作用的响应方式都略有不同，因此多元素方法比传统的元素周期表方法具有许多优势，因为在传统方法中，元素周期表的潜力没有得到充分开发。自然系统的分析将以高压和温度实验为基础，以建立上升弧岩浆的相关系和捕捉某些相元素亲和力的分配系数。由于流体聚集和运移是矿床形成过程中的一个基本步骤，但人们对此知之甚少，因此我们将与地球化学一起开发含流体糊状系统的数值模型。最后，将考虑关键金属，这些金属是主要成矿过程中的乘客，但构成斑岩矿化的重要副产品，往往未得到充分勘探。拟议的研究具有很强的蓝天调查元素，但特别关注通过改进勘探工具使行业受益的结果。因此，该项目以一种通常不可能通过行业资助的项目的方式弥合了学术研究和应用研究之间的鸿沟。这一衔接活动是重点专题呼吁的核心，特别是通过整合矿物系统研究、火成岩岩石学和地球化学方面的新进展，以期确定可作为新目标探路者的条件。一项关键成果将是一系列微量元素替代物，这将使采矿业能够在地方和区域范围内确定岩浆弧的潜在丰度。

Society is dependent on a reliable supply of metals and minerals for economic growth, improved standards of living, and development of infrastructure. Population growth means that even with increased recycling and resource efficiency, new mineral deposits still need to be discovered. The efficient exploration for, and discovery of, new resources requires new concepts and new tools. The Mineral Systems approach to exploration considers ore deposits on a lithospheric scale, in terms of the "ingredients", processes and environments that favour their formation. This approach amounts to a "source-pathway-trap" model, with an increased emphasis on predictive capacity, rather than just feature recognition. Historically, much research has focused on the trap, and characterisation of the ore deposits themselves; here we aim to focus deeper in the system by integrating ore deposit formation with concepts of magmatism that arise from igneous petrology and volcanology. Therein lies a challenge because extant models for porphyry systems are increasingly at odds with magmatic models for crustal construction and arc volcanism. Rather than seeing magmatic systems in terms of large, liquid-rich magma chambers, emerging petrological models for crustal magmatism are turning instead to crystal-dominated, volatile-bearing "mushy" systems that traverse most or all of the crust. The dynamics of such systems have important consequences not just for arc magmatism, but also for the chemistry of the volatiles that are exsolved. These same volatiles fuel mineralisation and this is the synergy that we aim to exploit by assembling a multidisciplinary team of researchers from economic geology, igneous and metamorphic petrology, volcanology, geochemistry, numerical modelling and fluid dynamics. Our team embraces almost everyone currently engaged in porphyry mineralisation research in the UK and capitalises on strong existing links between UK ROs and the mining industry, many of who are Project Partners. The research will involve analysis of minerals from a wide variety of mineralised and barren settings using a wealth of modern analytical tools that enable determination of an extensive suite of trace elements and isotope tracers. As each trace element responds to magmatic processes in subtly different ways due to the affinity of different elements for different phases (minerals, melts and fluids), so the multi-element approach affords many advantages over conventional proxies in which the full potential of the Periodic Table is not exploited. The analysis of natural systems will be underpinned by high pressure and temperature experiments to establish the phase relationships of ascending arc magmas and the partition coefficients that capture the affinities of elements for certain phases. As fluid accumulation and migration is an essential, but poorly understood, final step in ore deposit formation, we will develop, in tandem with the geochemistry, numerical models for fluid-bearing mushy systems. Finally, consideration will be given to critical metals that are passengers through the main ore-forming processes, but constitute important, often under-explored, by-products of porphyry mineralisation. The research proposed has a strong element of blue skies investigation, but a particular focus on outcomes that will benefit industry through improved exploration tools. Thus the project bridges the divide between academic and applied research in a way that is not normally possible through industry-funded projects. This bridging activity lies at the heart of the Highlight Topic call, specifically through the integration of new advances in the study of mineral systems, igneous petrology and geochemistry, with a view to identifying conditions that can act as pathfinders for new targets. A key outcome will be a range of trace element proxies that will enable the mining industry to establish the potential fertility of a magmatic arc on local to regional scales.