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。在气候不断变化的世界里，它们对于减少我们的碳足迹的技术至关重要。然而，矿藏稀少，而且越来越难找到，最优质(影响最小)的资源可能埋在长达一公里的贫瘠岩石下。每千个已发现的探矿中只有一个最终被开发成矿山，而这种探明已经对环境产生了影响，并消耗了大量资源。因此，在勘探的早期阶段认识到特定岩带的潜力(“肥力”)对于降低风险、成本、能源消耗和环境影响至关重要。然后在深部寻找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铜、钼和金的主要来源，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中的岩浆生成有关，俯冲带是地球上大多数大陆形成的地方。在这些弧中产生的岩浆大多喷发形成火山或作为贫瘠的深成岩浆侵位在深处。它们很少会以一种能够产生大量高金属含量水的方式进行改造。然而，我们对触发这种变化的原因的了解是有限的。钛铁矿是火成岩中常见的副矿物，经常出现在斑岩系统中。在这些矿床周围的热液蚀变带中也发现了它。它之所以令人感兴趣，是因为它可以记录使弧状岩浆肥沃的触发事件，还可以充当热液演化的非凡探测器，跟踪流体从矿藏迁移出来时性质的变化。在勘探过程中，这种梯度可以追溯到矿体本身的“上游”。由于它是一种相当坚硬的矿物，它能经受风化并集中在水系沉积物中，因此可用于区域勘探筛选。该项目的目标是从选定的贫瘠和富含的岩浆弧以及从一个严格约束的矿化系统的蚀变带中建立火成岩中的钛铁矿化学及其结晶历史。我们还将利用由凯斯合作伙伴提供的全球超过25个地点的钛铁矿颗粒的非凡档案。对这一独特的样品组的分析将使我们能够识别和了解控制弧丰度的岩浆演化的差异，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开发一个过程模型，解释典型的弧岩浆是如何转化为成矿系统的。实际上，识别肥力指纹和矿物化学梯度将为勘探提供强大的工具，这可能对风险和成本产生重大影响。这些对斑岩-铜矿勘探者至关重要，这就是为什么力拓愿意承诺约76,000英镑的现金和实物资源。力拓是国际采矿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，是一家全球性的多种商品资源公司，倡导对社会和环境负责的采矿。大型斑岩铜(金-钼)系统是四大洲的主要聚集区。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，社会必须对日益增长的自然资源压力做出紧急反应。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.