Developing sustainable mineral exploration targeting tools: titanite as an exploration guide and probe of porphyry ore system fertility

矿藏是支撑现代社会的金属来源。在一个气候不断变化的世界里，它们对减少碳足迹的技术至关重要。然而，矿藏稀少，而且越来越难以找到，质量最好（影响最小）的资源可能埋藏在长达一公里的贫瘠岩石下面。每一千个被发现的勘探区中只有一个最终被开发成矿山，而这种勘探区的确定已经影响了环境并消耗了大量资源。因此，在勘探的早期阶段认识到特定岩石带的潜在禀赋（“生育力”）对于降低风险、成本、能源使用和环境影响至关重要。在深度定位矿床的挑战代表了可持续矿产勘探的新前沿。斑岩型矿床是人类利用的大部分铜、钼和金的来源，也是关键环境技术中使用的关键元素的重要储存库。它们的形成与俯冲带的岩浆产生有关，地球上大部分大陆都是在俯冲带形成的。在这些弧中产生的岩浆大多被喷发形成火山，或在深处形成贫瘠的岩浆。很少会发生这样的转变，使它们能够产生大量富含金属的水。然而，我们对触发这种变化的原因的理解是有限的。钛矿是火成岩中常见的副矿物，常赋存于斑岩体系中。它也存在于这些矿床周围的热液蚀变带中。它的有趣之处在于它可以记录弧岩浆形成的触发事件，而且它还可以作为热液演化的非凡探测器，跟踪流体从矿床迁移时性质的变化。在勘探中，这种梯度可以追溯到“上游”矿体本身。由于它是一种相当坚硬的矿物，可以经受风化作用，并且可以集中在水系沉积物中，因此可以用于区域勘探筛选。本项目的目标是在选定的贫瘠和资源丰富的岩浆弧中以及在一个约束良好的矿化系统的蚀变带中建立火成岩中的钛矿化学及其结晶历史。我们还将利用CASE合作伙伴提供的来自全球超过25个地点的出色的钛矿颗粒档案。对这一独特样品组的分析将使我们能够识别和了解控制弧肥力的岩浆演化差异，并表征矿化系统周围存在的矿物化学梯度。我们的主要科学目标是建立一个过程模型，解释典型的弧岩浆如何转变为成矿系统。实际上，识别生育力指纹和矿物化学梯度将为勘探提供强有力的工具，这可能对风险和费用产生重大影响。这对斑岩铜矿勘探人员来说是至关重要的，这就是为什么里约热内卢Tinto愿意投入约76,000磅的现金和实物资源。b里约热内卢Tinto是国际矿业和金属理事会的成员，致力于联合国全球契约及其支持原则，是一家全球性的多商品资源公司，率先对社会和环境负责任的采矿。大型斑岩Cu-(Au-Mo)系统是四大洲的主要焦点。因此，研究大型斑岩铜系统的成因与其活动直接相关。各国政府现在认识到，社会必须紧急应对日益增加的自然资源压力。为了迎接这一挑战，社会必须以可持续的方式发现和开发资源，我们的建议旨在为这些重要目标做出贡献。

Ore deposits are the source of metals that underpin modern society. In a world with a changing climate, they are critical for the technologies that reduce our carbon footprint. However, ore deposits are scarce and increasingly difficult to find, with the best quality (lowest impact) resources likely to be buried beneath up to a kilometre of barren rock. Only one in every thousand prospects that are discovered is eventually developed into a mine, and the identification of such prospects has already impacted the environment and consumed significant resources. Consequently, recognizing the potential endowment ('fertility') of a particular belt of rocks at an early stage of exploration is essential for reducing risk, costs, energy use and environmental impacts. The challenge of then locating deposits at depth represents the new frontier of sustainable mineral exploration.Porphyry-type ore deposits source much of the copper, molybdenum and gold utilized by humankind, and are also important repositories of critical elements used in key environmental technologies. Their formation is related to magma generation in subduction zones, the place where most of Earth's continents are created. Magmas produced in these arcs are mostly erupted to form volcanoes or are emplaced at depth as barren plutons. Rarely, they are transformed in such a way that they become capable of generating vast volumes of highly metalliferous waters. However, our understanding of what triggers this change is limited.Titanite is a common accessory mineral in igneous rocks and often occurs in porphyry systems. It is also found in the hydrothermal alteration zones that surround these deposits. It is of interest because it could record the trigger events that fertilise arc magmas, and it could also act as a remarkable probe of hydrothermal evolution, tracking the changes in properties of fluids as they migrated away from the ore deposit. In exploration, such gradients can be tracked back 'upstream' to the orebody itself. Because it is a fairly hard mineral, it survives weathering and can become concentrated in stream sediments, thus could be used in regional exploration screening.The objectives of this project are to establish titanite chemistry and its crystallization history in igneous rocks from selected barren and well-endowed magmatic arcs and from across the alteration zone of a well-constrained mineralized system. We will also utilize a remarkable archive of titanite grains from more than 25 sites worldwide, provided by the CASE partner. Analysis of this unique sample suite will allow us to identify and understand differences in magmatic evolution that control arc fertility and to characterize the mineral chemistry gradients present around mineralized systems. Our primary scientific aim is to develop a process model that explains how typical arc magmas become transformed into ore-generating systems. In practical terms, the recognition of a fertility fingerprint and of mineral chemistry gradients would provide powerful tools for exploration that could impact significantly on risk and costs. These are of paramount importance for porphyry-Cu explorers which is why Rio Tinto are willing to commit cash and in-kind resources of approximately 76,000 pounds. Rio Tinto, a member of the International Council on Mining and Metals, committed to the United Nations Global Compact and its supporting principles, is a global, multi-commodity resource company that pioneers socially and environmentally responsible mining. Large porphyry Cu-(Au-Mo) systems are a primary focus on four continents. Thus, research into the genesis of large porphyry Cu systems is directly relevant to its activities.Governments now recognise that society must respond urgently to the increasing pressures on natural resources. To meet this challenge, society must discover and develop resources in a sustainable way and our proposal aims to make a contribution to these important objectives.