Explore the vast range of titles available.

Immiscibility between water and hydrogen-rich fluids may be responsible for the formation of super-reduced mineral assemblages and for the early oxidation of Earth´s upper mantle. In the current study, we present new data on the critical curve in the H2-H2O system to 1400 ℃ and 4 GPa. We utilized a synthetic fluid inclusion method to trap fluids at high P–T conditions within quartz and olivine crystals. Experiments were performed in a piston-cylinder type apparatus, employing a double-capsule technique. The inner capsule contained the crystal and fluids of interest, while the outer served as oxygen fugacity buffer, maintaining f(O2) at the iron-wüstite (Fe-FeO) equilibrium. Our results suggest that below ~ 2.5 GPa, the critical curve has a mostly linear slope of 200 ℃/GPa, while at more elevated pressure it becomes significantly steeper (400 ℃/GPa). This implies that in most of the modern, reduced upper mantle, water and hydrogen are immiscible, while localized heating events, such as rising plumes, may close the miscibility gap. The steep increase of the critical curve at high pressure observed in this study implies that even for very hot geotherms in the early Archean or the late Hadean, H2-H2O immiscibility likely occurred in the deeper parts of the upper mantle, thus making a plausible case for rapid H2 loss as a mechanism of early mantle oxidation. To constrain the geochemical fingerprint of this process, we performed a series of element partitioning experiments to unravel how the H2-H2O unmixing may affect element transfer. Noble gases such as Xe as well as methane are preferentially incorporated in the hydrogen-rich phase, with a XeH2O/XeH2 ratio of ~ 8. This partitioning pattern may, for example, explain the underabundance of Xe isotopes produced by fission of Pu in the mantle. These Xe isotopes may have been removed by a primordial H2-H2O unmixing event during the early stages of planetary evolution.

Global copper supply faces systemic challenges, mainly from geographically concentrated reserves, aging mines and declining ore grades. One way to help overcome these issues is with technology. In this study, we present a new, open‐source global copper deposit dataset (GCDD), facilitating artificial intelligence‐driven data analysis for exploration targeting and improving our understanding of copper mineralizing systems and their mappable expressions. The newly developed GCDD hosts information about 1483 copper deposits worldwide, capturing key deposit attributes such as location, genetic type, metallogenic age, mineral assemblage, grade and tonnage. Rigorous manual validation procedures ensured data accuracy and consistency. The GCDD, intended as a standardised, comprehensive resource for copper deposit exploration and geoscientific research, was established by systematically integrating copper deposits information from three authoritative open‐source databases: Mindat, MRDS, and the Mineral Evolution Database. The data extracted from these sources were supplemented with information sourced from peer‐reviewed literature. Whilst Mindat, MRDS and the Mineral Evolution Database each contain important copper deposit data, they lack standardised genetic classifications and quantitative mineralogical records and, therefore, do not lend themselves well to exploration targeting or advanced modelling. The GCDD, on the other hand, supports both (i) traditional metallogenic studies and resource assessments, and (ii) advanced analyses such as network‐based mapping of mineral co‐occurrence patterns and association rule mining to uncover intrinsic links between mineral assemblages and copper deposit types. As such, it can facilitate critical mineral assessment, spatiotemporal metallogenic analysis, and data‐driven exploration targeting of sustainable future copper supply.

In the SE Alps, two Cretaceous–Eocene flysch basins, Julian and Brkini, filled with turbidite sediments, are present. This study novelly reports heavy mineral assemblage counts and detrital tourmaline characterization for 11 samples. It is possible to define three different groups, characterized by the presence of (1) a clinopyroxene–epidote–low-ZTR (zircon+tourmaline+rutile; 5%) sample association, (2) a high-ZTR (>48%)–garnet–apatite association and (3) a low-ZTR (<40%)–Cr-spinel–garnet association. Detrital tourmalines from both the Julian and Brkini flysch basins are rather similar in composition, associated with metapelites and metapsammites coexisting or not coexisting with an Al-saturating phase, ferric-iron-rich quartz–tourmaline rocks and calc–silicate rocks; however, their number is drastically different. In fact, even if the percentage of heavy minerals is very low and similar in both basins (0.17–1.34% in weight), in the Julian basin, the number of tourmaline crystals is much lower than that in Brkini (1–14 vs. 30–100), suggesting an important change in the provenance area. Interestingly, the presence of a high amount of tourmaline derived from ferric-iron-rich quartz–tourmaline rocks and calc–silicate rocks makes these two basins different from all the Cretaceous flysch basins of Bosnia and the Northern Dinaric zone, where these supplies are missing or very limited.

This study focuses on the Hailijing sandstone-hosted uranium deposit in the Songliao Basin. Through a combination of petrographic analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and geochemical analysis, the epigenetic alteration of the deposit was systematically investigated, and the alteration zonation was delineated. On this basis, the metallogenic mechanisms were further explored. The results indicate that six major types of alteration can be identified in the ore-bearing strata of the Hailijing uranium deposit: hematitization, limonitization, carbonatization, pyritization, clay mineralization (including kaolinite, illite, and illite-smectite mixed-layer), and baritization. The mineral assemblages at different stages of alteration vary: during the sedimentary diagenetic stage, the assemblage consists of “hematite + clay minerals + II-type pyrite (framboidal pyrite) + III-type pyrite (euhedral granular pyrite)”; during the uranium mineralization stage, it transitions to “ankerite + barite + I-type pyrite (colloidal pyrite) + minor kaolinite”; and in the post-ore stage, alteration is characterized by calcite cementation in red sandstones. Based on petrological, mineralogical, and geochemical characteristics, as well as the spatial distribution of the host gray sandstones, it is inferred that during uranium mineralization stage, the ore-bearing strata underwent reduction by uranium-rich reducing fluids sourced from the Lower Cretaceous Jiufotang Formation. The primary red sandstones of the Lower Yaojia Formation, formed under arid to semi-arid conditions, experienced varying degrees of reduction, resulting in a color transition from light red, brownish red, and yellowish brown to grayish-yellow and gray. Accordingly, four alteration zones are distinguished in the Hailijing uranium deposit: the primary red zone, weakly reduced pink zone, moderately reduced grayish-yellow zone, and strongly reduced gray zone. Furthermore, as the uranium-rich reducing fluids migrated from a high-temperature, high-pressure deep system to the low-temperature, low-pressure ore-bearing sandstone strata near the surface, uranium was unloaded, precipitated, and enriched, ultimately forming multi-layered and tabular-shaped uranium orebodies within the gray sandstone. This study elucidates the epigenetic alteration processes and metallogenic mechanisms of the Hailijing uranium deposit, providing a critical theoretical basis for further uranium exploration in the southern Songliao Basin.

Cold seeps create diverse habitats in the deep sea and play an important role in the global carbon cycling. Anaerobic oxidation of methane (AOM) and biogenic mineralization are essential carbon pathways of methane and carbon transformation in cold seeps, however, the effects of habitat heterogeneity on the processes are still poorly understood. In this study, we investigated the microbial communities and mineral assemblages at distinct habitats in the Haima cold seep and their relationships with environmental factors. These habitats were classified as methane seep site (MS), seep-free faunal habitat (FH), and control site (CS). Bacterial communities were significantly different among the three habitats. ANME-3 archaea, Sulfurovum bacteria, and mineralization-associated microbes (e.g., Campylobacterales) were detected in high relative abundances at ROV2. Mineralogical analysis revealed abundant calcite minerals at the seep site, indicating that authigenic carbonate minerals were formed at highly active seep. Multivariate statistical analysis demonstrated that the concentrations of SO 4 2– , Ca 2+ , and Mg 2+ were significantly correlated with the presence of calcite minerals and bacterial communities. These results suggested that AOM-accompanied authigenic carbonate formation is an important factor influencing the mineral assemblages in seep habitats. This finding improves our understanding of marine microbial carbon cycling.

The Jiadi and Damaidi gold deposits in southwest Guizhou Province are the largest basalt-hosted Carlin-type gold deposits recently discovered in China. This study uses the Tescan Integrated Mineral Analyzer, supported by detailed field investigations, regional geological data, and extensive sample collections, including mineralized ore, altered wall rock, and unaltered basalt samples, for ore-bearing and geochemical analyses. Comparative analysis between altered and unaltered basalt samples revealed a mineral assemblage of sericite, quartz, and pyrite. This mineral composition forms through the hydrothermal alteration of unaltered basalt, originally containing feldspar, pyroxene, and ilmenite. The wall rock primarily features sericite, quartz, and hematite. During the alteration process, major, trace, and rare earth elements notably migrate. In the Jiadi deposit, K 2 O, Rb, Au, and REE significantly increase, while Na 2 O, CaO, MgO, and MnO decrease. SiO 2 , Al 2 O 3 , and Fe 2 O 3 levels remain relatively stable. In the Damaidi deposit, K 2 O, Rb, and Au enrich, contrasting with the depletion of Na 2 O, CaO, MgO, and MnO, while SiO 2 , Fe 2 O 3 , Al 2 O 3 , TiO 2 , and REE show no significant changes. In the wall rock, TiO 2 , Al 2 O 3 , K 2 O, and REE increase, while Na 2 O, CaO, MgO, and MnO decrease; SiO 2 and Fe 2 O 3 content remains unchanged. The mineralization process likely originated from mid- to low-temperature, reductive magmatic hydrothermal fluids rich in CO 2 , CH 4 , N 2 , H + , S 2− , HS − , H 3 AsO 3 , and [Au(HS) 2 ] − . These fluids migrated to tectonically weak zones in the Lianhuashan area, where Emeishan basalts are present. They reacted with Fe-bearing minerals in the basalt, such as ferro-hornblende and ilmenite, forming pyrite, arsenic-bearing pyrite, and arsenopyrite, thus enriching Au in these minerals. Additionally, K + and H + in the fluid reacted with plagioclase in the basalt, forming sericite and quartz. As the fluid entered the wall rock from structural weak zones, its oxidation increased, leading to the complete or partial reaction of Fe-bearing minerals in the wall rock, resulting in the formation of hematite or magnetite. This mineralization process is similar to that observed in carbonate-hosted Carlin-type gold deposits in southwest Guizhou, with the primary distinction being the iron source. In carbonate deposits, iron originates from ferridolomite within the wall rock, while in basalt-hosted deposits, it derives from ferripyroxene and ilmenite.

The Lesser Zab River (LZR), the largest tributary in Iraq, with a catchment area of about 20,000 km2, and majority of its basin lying in Iraq, drains into the Tigris River. It runs through highly folded and faulted igneous and metamorphic zone in the northeastern part of Iraq. We studied the heavy minerals in recent sediments of the Lesser Zab River Basin (LZRB) to determine their mineralogies, assemblages pattern, distribution manner, spatial variability, microtexture, provenance, and tectonic setting. We analyzed 24 sediment samples for heavy mineral assemblage determination, using the standard petrographic method. Scanning Electron Microscopy was used to determine the morphology of the grains of selected heavy minerals. Heavy minerals identified in the studied sediments include: dark color such as magnetite, ilmenite, hematite, and goethite; and transparent minerals represented by hornblende, tremolite–actinolite; pyroxenes, epidotes, zircon, tourmaline, rutile, garnet, staurolite, kyanite, and layered minerals assemblage such as muscovite, chlorite, biotite, and phlogopite. The studied sediments are considered immature, because they have the lowest concentration of ultrastable minerals compared to unstable heavy minerals, which confirms that the surface sediments of LZR and its sub-basin tributaries were deposited in an active continental-margin tectonic setting.

The heavy mineral assemblage (HMA) of sandstones belonging to Mesoproterozoic Kaimur Group in the eastern Son valley, Central India, was investigated. The present communication is aimed at assessing mineralogical maturity, quantifying the contribution of heavy fraction to the bulk rock and its REE budget, sediment recycling and provenance. The transparent heavies record a relative decreasing trend upwards from 63 to 36.4% and on the contrary, opaque heavies show gradual increasing trend upwards from 36.4 to 65.4%. Tourmaline in the transparent heavy fraction reveals an overall decreasing trend of 59–22.8%. Whereas, zircon registers an increasing trend of 3.3–9.5% stratigraphically upwards. The contribution of opaque detrital clasts of ferruginous material composed of hematite and magnetite increases in the Upper Kaimur Sandstone. Tourmaline and zircon grains are characterised by etched, pitted and grooved surfaces. Zircon is also present as tiny inclusion within tourmaline and zircon itself. Heavy fraction of Upper Kaimur sandstone from the lower stratigraphic horizon exhibit lower ∑REE as compared to higher levels. The heavy fraction exhibit LREE/HREE < 1 as compared to bulk rock which has 8–10 times higher ratio. Heavy fraction exhibits enrichment in HREE and [Gd/Yb] N = 0.36–0.43, stratigraphically upwards, which is consistent with increasing Zr values suggesting zircon to be the major contributor to the REE budget of Upper Kaimur Sandstones. The percentage contribution of the zircon to the REE budget of bulk rock could have been ~50–60%. ZTR index (99–100) reveals mineralogically mature nature of Kaimur sandstones. Dominance of zircon amongst the heavies and Th/Sc vs. Zr/Sc plot shows the effect of zircon addition and sediment recycling. The plausible explanation for dominance of opaque minerals in HMA in the Upper Kaimur reflects their contribution from Paleoproterozoic metasedimentary rocks of Mahakoshal Group. HMA of Kaimur sandstones suggests derivation from granitic source. Nb/Yb vs. U/Yb diagram indicates that zircon was derived from magmatic arc source, which is in conformity with inference that Bundelkhand Granite Complex and Chhotanagpur Granite complex dominantly contributed to the Lower and Upper Kaimur Groups, respectively. Research highlights The paper deals with the study of heavy mineral assemblage of the Kaimur Group sandstones, Vindhyan Supergroup, Son Valley, Central India. Provenance, sorting and recycling of the sediments were inferred. The ferruginous clasts found in the Dhandraul Quartzite/Sandstone also have been studied to understand their mineralogy and texture. Tourmaline and zircon dominate the Lower and Upper Kaimur Sandstones, respectively. The provenance of the Lower Kaimur sandstones is Bundelkhand granite, and Upper Kaimur sandstone is Chhotanagpur Gneissic Complex. The dominance of zircon in HMA and Th/Sc vs. Zr/Sc plot shows the significant effect of zircon addition and sediment recycling. The occurrence of ferruginous detrital clasts in Upper Kaimur sandstones can be attributed to increasing detrital input from adjoining Mahakoshal Group that has the presence of BIFs/BHQ/BHJ in the Agori Formation. The heavy fractions from sandstones of Mangesar Formation and Dhandraul Quartzite from different horizons exhibit an increase in Zr and HREE stratigraphically upwards. This suggests remarkable enrichment of HREE, low LREE/HREE, [La/Yb] N <1 and [Gd/Yb] N <1. HREE enrichment is proportional to the Zr concentration signifying the dominant role of zircon amongst the heavies in managing the ΣREE budget of the bulk rock. The percentage contribution of the zircon is calculated to be ~50–60%.

Viviparus beds are sediments deposited in lacustrine and fluvial freshwater environments (Lake Slavonia) during the Pliocene and the earliest Pleistocene. A detailed field study and mineralogical, petrographic and chemical analyses were carried out to determine their composition and origin in the area of Vukomeričke Gorice, Central Croatia. Viviparus beds are characterized by the vertical and lateral exchange of mineralogically and chemically mature pelites and sands. Pelitic sediments consist mainly of detrital quartz, calcite, dolomite and feldspar grains, with smectite as the most common clay mineral. Quartz and the most resistant lithic fragments dominate the sandy detritus. The composition of the sediments indicates their origin from the recycled orogen, while their textural immaturity suggests a short transport distance. Most of the material was re-deposited from the underlying Upper Miocene sediments, originally of Alpine provenance. A lesser proportion originated from Palaeogene sediments, Triassic carbonate rocks, basic or acidic magmatic rocks and metamorphites. The Medvednica and Žumberak Mts. were the most important source areas, while a smaller proportion of the material could have come from the Moslavačka gora Mt. and Banovina region. The uniform composition of the Viviparus beds over the entire vertical distribution of the sediments clearly indicates that the source areas did not change during their deposition. A significant change from the texturally and compositionally mature Upper Miocene clastic detritus of alpine origin, to the texturally immature material of the Viviparus beds of local origin is a consequence of compression and inversion of the previously extensional basin resulting in the uplifting and erosion of the mountains within the SW part of the Pannonian Basin System.

To understand the relationships between eclogite-facies mineral assemblages, deformation microstructures, and the seismic properties of subducting oceanic crust, eclogites from the Yuka terrane, North Qaidam ultrahigh-pressure metamorphic belt, NW China were studied. Observations of mineral textures, deformation microstructures, and petrofabrics in the eclogites indicate that garnet, omphacite, and phengite were deformed by intra-crystalline deformation (i.e., dislocation creep) during prograde metamorphism. In contrast, amphibole, which was formed by the topotactic replacement of omphacite at fluid-present conditions, is considered to have been deformed by diffusional flow (dissolution–precipitation creep) during amphibolite-facies retrogression associated with exhumation. Based on the petrofabrics in the samples, the seismic properties of the eclogites were calculated depending on eclogite-facies mineral assemblages such as garnet + omphacite (GO), garnet + omphacite + phengite (GOP), garnet + omphacite + phengite + lawsonite (GOPL), garnet + omphacite + phengite + amphibole (GOPA), and garnet + omphacite + amphibole (GOA). We found that the seismic signatures of each of the eclogite-facies mineral assemblages were different. In particular, phengite-bearing eclogites (the GOP/GOPA assemblages), depending on phengite content, produced the strongest seismic anisotropy (AVp and AVs), with a strong polarization anisotropy, that was at least three times higher than bimineralic (phengite-absent) eclogite (GO assemblage). Our results show that phengite, as a stable phase at high pressure and temperature conditions, can play an important role in the creation of trench-parallel seismic anisotropy in the eclogite-facies mineral assemblages found in subduction zones.