Editorial: Ore formation and critical metal deposits: geological contribution to the clean energy transition

Many chalcophile (sulfur-loving) and siderophile (iron-loving) elements are defined as critical metals based on their economic importance and potential supply risks. For these metals, demand already exceeds or is expected to exceed the supply. Critical metals are involved in high technologies and clean energies. The most outstanding example is undoubtedly the elements required for the transition to low-carbon emissions technologies and the electrification of transport. Additionally, critical metals enter the composition of superalloys and other high-tech materials for the fabrication of high-technology applications in medicine, aerospace, and telecommunications.Humanity faces serious problems such as global warming, pollution, and poverty. Earth sciences cover a broad range of research studies to tackle these problems. Scientists have recently started investigating critical metal deposits' metallogenesis and related minerals' metallurgy, but the essential information is still missing. Chalcophile and highly siderophile metals fractionate in magmatic and hydrothermal processes forming different types of ores. The partitioning of metals between silicate melts, minerals, and fluids strongly depends on intensive parameters, such as temperature, pressure, oxygen, and sulfur fugacities, as well as the composition of melt, fluid, and sulfide phases, all of which may change significantly during the evolution of magmatic-hydrothermal systems. Hence, the partitioning behavior varies in tectonic settings, such as mid-ocean ridges, oceanic islands, subduction zones, flood basalt provinces, and continental rift zones, leading to differences in metallogenic processes and ore type. Furthering our understanding of metal speciation and partitioning behavior can provide new insights into large-scale geodynamic processes and the concentration of strategic metals at a local scale. This Research Topic collects interdisciplinary papers contributing to various aspects of these processes, including petrology, experimental petrology (Helmy et al., 2024), mineralogy, geochemistry, ore geology, economic geology (Bertrandsson Erlandsson et al., 2023; Boucher et al., 2023; Robb et al., 2023), and planetary geology (Ciazela et al., 2023).Platinum-group elements (PGE) form an important group of critical raw materials. Contributions in this Research Topic related to PGEs were provided by Helmy et al. (2024), Boucher et al. (2023), and Robb et al. (2023). The major hosts of Pt and Pd in magmatic and hydrothermal Cu-Ni-sulfide ores are sulfides, arsenides, antimonites, tellurides, and bismuthides. To better understand which and when Pt or Pd phases form from Ni-Cu sulfide melts dopped with different amounts of semimetals (As, Te, Bi, and Sb), Helmy et al. (2024) have designed an experimental approach consisting of slow cooling from 1100 ºC to room conditions of these sulfide melts and then to observe and analyze the coexisting phases at different programmed temperatures. Boucher et al. (2023) present a large volume of data regarding the distribution of PGEs in pyrite in the New Afton alkali porphyry Cu-Au deposits in Canadian Cordillera complemented by extensive trace element and sulfur isotope data in pyrite. They set the stage for the companion paper by Robb et al. (2023), which addresses the geochemical controls on PGE deposition and spatial distribution in the same deposit. Robb et al. (2023) present the first comprehensive look at the distribution of Pd and Pd in a porphyry deposit with grade shells in a resource model, and it is the first to present a thermodynamic model for the co-precipitation of PGEs with pyrite in hydrothermal systems.Cobalt is another element with rapidly growing demand. New alternative sources will soon be needed to satisfy this demand. Many expectations are related to the mining of polymetallic nodules on the seafloor. Only polymetallic nodules from the Clarion-Clipperton basin contain three to six times more cobalt than all the land reserves, according to the 2021 reports of the International Renewable Energy Agency and World Ocean Review. However, ecological concerns related to seabed life and technical concerns related to ship post-processing still hamper those endeavors, and new land sources will be needed before we start exploring the oceans. Sphalerite hosts many critical metals, including Ga, Ge, and In. Nevertheless, Co had not been found at such high concentrations as at the sediment-hosted copper-cobalt Dolostone Ore Formation deposit, Namibia, which was investigated by Bertrandsson Erlandsson et al. (2023). Hence, it is vital to understand the mode of occurrence of this cobalt and better understand the geological formation processes responsible for it.Space mining also needs critical metals on Earth to develop spaceship and space habitat infrastructure to be sent into space. More importantly, local resources of essential metals will be required on the Moon to avoid costly transportation from Earth. Due to the high cost, importing iron and copper from the Moon will be impractical. However, their in situ presence for future human activities will save the Earth's resources for climate action instead of sending them to space in large amounts for exploration and other purposes. Despite the growing interest in space mining of asteroids and planetary bodies, directly detecting sulfides and oxides from orbits was an unexplored field as they were undetectable from orbits in the previously developed near-infrared (NIR) spectroscopy. However, currently developed far-IR (FIR) spectroscopy may offer rich possibilities for detecting ore minerals from orbit, especially on the Moon, where interferences with atmospheric water are not an issue (Ciazela et al., 2023). Therefore, the contributions to this Research Topic, organized in collaboration with the Commission on Ore Mineralogy of the International Mineralogical Association, improve our understanding of ore-forming processes, metal distribution, and their role in solving global economic and ecological problems. We thank the contributors and reviewers who made this special issue possible.

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