Mineralium Deposita最新文献

The S saturation and oxidation states of arc magmas are important factors in the formation of porphyry Cu–Au deposits. The Milin juvenile lower crustal cumulates (86.7–84.3 Ma) in the Gangdese provide insights into how sulfide saturation and oxidation states control porphyry mineralization. Zircons from the cumulates have low Ce⁴⁺/Ce³⁺ ratios (21–90) and reduced oxygen fugacities (ΔFMQ–1.8±0.5), which cannot be explained by fractional crystallization or crustal contamination, suggesting inheritance from a mantle source. Partial melting of the mantle under reduced conditions produced a sulfide-saturated primary arc magma with low chalcophile element contents owing to the residual sulfide in the mantle. The Milin lower crustal cumulates contain sulfides, indicating that the magma reached sulfide saturation in the early stages of magmatic differentiation. Based on our model, the primary arc magma before sulfide saturation contained 66.7 ppm Cu and 1.0 ppb Au. The residual magma after sulfide saturation in the lower crust contained 33–66 ppm Cu, 0.13–0.93 ppb Au; i.e., lower contents than those in arc basalts worldwide. Both these factors hindered the formation of Late Cretaceous large porphyry Cu–Au deposits in the Gangdese belt. Remelting of the Milin sulfide-rich cumulates can generate a Cu-rich andesitic magma only under high temperature and high-fO₂ conditions, and a melt with low Cu content under low temperature even high-fO₂ conditions. Thus, the temperature plays a crucial role in the remelting of the lower crust whether provide enough metals to match the Gangdese Miocene post-collisional porphyry Cu deposit.

The Lautenthal sphalerite-galena vein deposit is part of the world-class Upper Harz Pb-Zn-Ag district in the Harz uplift block of the Paleozoic Variscan fold belt in Germany. Its sphalerite-dominated mineral association was studied using bulk-ore chemistry, electron probe microanalysis, and laser ablation-ICP-mass spectrometry. Gallium and locally In are the main high-tech-relevant trace elements hosted by sphalerite, with up to 150 ppm Ga and up to 380 ppm In in hand-picked sphalerite samples (mean In/Zn, 0.70 × 10⁻³). Ore concentrates (≤ 50 kg) contain up to 65 ppm Ga and up to 109 ppm In (mean In/Zn, 0.36 × 10⁻³). Accessory Fe-Co-rich gersdorffite-1 occurs in the earlier quartz-sulfide ore stage and Sb-rich gersdorffite-2 in the later carbonate-sulfide stage. Enrichment patterns of In are either defined by overprinting textures in the Fe-richer sphalerite-1 of the earlier stage, or relate to primary growth zoning in Fe-poor sphalerite-2 of the later stage. Using the sphalerite geothermometer GGIMFis, formation temperatures (median) of sphalerite-1 were estimated at ~ 230 °C for the Lautenthal orebody and at ~ 175 °C for the Bromberg orebody, which may indicate lateral T-zonation for the earlier ore stage. Sphalerite-2 data indicate formation temperatures of ~ 185 °C (median). Copper-bearing brines of the carbonate-sulfide stage with assumed temperatures of ~ 250 °C initiated replacement of In-poor sphalerite-1 by chalcopyrite and remobilization of Zn and trace elements. Indium-rich sphalerite-2 occurs associated with calcite and fine-grained galena. A direct spatial or temporal link of ore formation to a magmatic-hydrothermal system is unlikely, which contrasts to In-rich epithermal and tin-polymetallic vein deposits worldwide.

The Bohemian Massif hosts significant hydrothermal U-deposits associated with shear zones in the high-grade metamorphic basement. But there is a lack of evidence of a genetic link between mineralization and U-fertile igneous rocks. This contribution provides constraints on the major U source of the vein-type U-deposits, the timing of ore formation and the metallogenetic model. The anomalous trace element signatures of the low-temperature hydrothermal deposits (high Zr, Y, Nb, Ti, ∑REE) and their close spatial relation with ultrapotassic rocks of the durbachite series point to a HFSE and REE enriched source rock. The durbachites have high U content (13.4–21.5 ppm) mainly stored in magmatic uraninite and other refractory minerals (e.g., thorite, zircon, allanite) that became metamict over a time interval sufficient to release U from their crystal structure, as suggested by the time gap between emplacement of the durbachites (EMP uraninite U–Pb age ~ 338 Ma) and hydrothermal activity (SIMS uranium ore U–Pb age ~ 270 Ma). Airborne radiometric data show highly variable Th/U ratios (1.5–6.0), likely reflecting a combination between (1) crystallization of magmatic uraninite, (2) hydrothermal alteration, and (3) leaching and mobilization of U along NW–SE-trending fault zones, manifested by elevated Th/U values in the radiometric map. The presence of rare magmatic uraninite in durbachites suggests almost complete uraninite dissolution; EMP imaging coupled with LA-ICP-MS analyses of refractory accessory phases revealed extensive mobilization of U together with HFSE and REE, providing direct evidence for metal leaching via fluid-driven alteration of radiation-damaged U-rich minerals. The large-scale HFSE and REE mobilization, demonstrated by the unusual trace element signatures of the U-deposits, was likely caused by low-temperature (270–300 °C), highly alkaline aqueous solutions containing F-, P-, and K-dominated complexing ligands. The first SIMS U–Pb age of 270.8 ± 7.5 Ma obtained so far for U-mineralization from the Bohemian Massif revealed a main Permian U mineralizing event, related to crustal extension, exhumation of the crystalline basement, and basin formation, as recorded by U–Pb apatite dates (280–290 Ma) and AFT thermal history models of the durbachites. The Permo-Carboniferous sedimentary cover probably represented a source of oxidized basinal brines infiltrating the basement-hosted durbachite plutons and triggering massive metal leaching. The interaction between basin-derived brines and durbachites resulted in significant modification of the chemical composition of the hydrothermal system (K and F release during biotite chloritization, P liberation through monazite alteration), leading to the formation of ore-bearing fluids responsible for the metallogenesis of the basement-hosted unconformity-related U-deposits in shear zones in the Bohemian Massif.

The Punta del Cobre district near Copiapó is a center of iron oxide-copper–gold (IOCG) mineralization spatially and temporally associated with regional sodic-calcic hydrothermal alteration, the Atacama fault system (AFS), and two phases of Early Cretaceous magmatism. Here, we investigate the spatiotemporal and geochemical relationships between magmatism, ductile deformation, and hydrothermal alteration along the ~ 200 to 300-m-thick steeply NW-dipping Sierra Chicharra shear zone, interpreted to be the major strand of the AFS. Mylonitic fabrics and oblique sinistral-reverse kinematic indicators together record coaxial flattening in a transpressional regime. Deformation on the AFS took place before, during, and after intrusion of the synkinematic Sierra Chicharra quartz diorite of the Coastal Cordillera arc at ~ 122 Ma and terminated before intrusion of the unstrained ~ 114 Ma Sierra Atacama diorite of the Copiapó batholith. Geochemical data show that the Copiapó batholith was more mafic and more K-rich than the calc-alkaline Coastal Cordillera arc. This time period thus overlaps IOCG mineralization in the Punta del Cobre district (~ 120 to 110 Ma). Multiple phases of sodic-calcic alteration in and around the AFS shear zone are recognized. Textures of altered rock in the shear zone show both synkinematic assemblages and post-kinematic hydrothermal oligoclase. A ~ 775-m-long andradite vein that cuts the shear zone formed broadly at the end of magmatism in the district (~ 95 Ma). Oxygen isotope ratios from the vein indicate that hydrothermal fluids were likely magmatically derived. Together, this work shows the AFS-related shear zone and nearby IOCG mineralization developed in a regional transpressional regime produced by SE-directed oblique convergence across a NE-striking shear zone. IOCG-related magmatic-hydrothermal fluids exploited this transcrustal shear zone to produce multiple episodes of regional sodic-calcic alteration formed from fluids exsolved from magmas or driven by the heat of the Coastal Cordillera arc and Copiapó batholith.

Determining the association of Pb–Zn(-Ag) mineralization with granite is crucial for understanding metallogeny and identifying exploration targets. The genesis of Pb–Zn-Ag-Sb deposits and their genetic association with Sb(-Au) deposits and granite-associated Sn-W deposits in the Tethys Himalaya of southern Tibet, China, remains controversial. Our comprehensive study of in situ element compositions and sulfur isotopes of sulfides, together with in situ quartz oxygen isotopes for the Zhaxikang Pb–Zn-Ag-Sb deposit, sheds light on this issue. LA-ICP-MS analyses of early sulfides in manganosiderite veins, coupled with C-O isotopes of manganosiderite, indicate that the early fluids were enriched in Pb, Zn, Ag, Sb, Sn, and Cu, originating from magmatic fluids mixing with meteoric water. The early formed sulfides underwent fluid-mediated remobilization and dissolution, releasing many metallic elements (e.g., Pb, Zn, and Ag) into later As-Sb-rich fluids. These elements reprecipitated as Fe-poor sphalerite, As-rich pyrite, and abundant Sb-Pb sulfosalts with minor Ag-bearing minerals. Oxygen isotopes of quartz indicate that the later fluids were derived from pulsed releases of magmatic fluids mixing with meteoric water. In situ sulfur isotopes of three generations of pyrite indicate that early Pb–Zn(-Ag) sulfide precipitation was linked to magmatic sulfur, whereas precipitation of the later sulfosalts and stibnite involved external sulfur with relatively lower sulfur isotopes compared with early mineralization. We argue that Pb–Zn-Ag-Sb deposits in the Tethys Himalaya resulted from two distinct mineralization pulses. The early Pb–Zn(-Ag) mineralization was associated with crustal magmatic rocks (e.g., leucogranite), followed by the overprinting of later Sb-rich magmatic fluids. Notably, the later magmatic fluids responsible for Zhaxikang Pb–Zn-Ag-Sb mineralization were also associated with the regional Sb(-Au) deposits in the Tethys Himalaya.

Seafloor massive sulfides form in various marine hydrothermal settings, particularly within volcanic arcs, where magmatic fluids may contribute to the metal budget of the hydrothermal system. In this study, we focus on the Kolumbo volcano, a submarine volcanic edifice in the central Hellenic Volcanic Arc hosting an active hydrothermal system. Diffuse sulfate-sulfide chimneys form a Zn-Pb massive sulfide mineralization with elevated As, Ag, Au, Hg, Sb, and Tl contents. These elements have similar behavior during magmatic degassing and are common in arc-related hydrothermal systems. Trace-element data of igneous magnetite, combined with whole rock geochemistry and numerical modelling, highlights the behavior of chalcophile and siderophile elements during magmatic differentiation. We report that, despite early magmatic sulfide saturation, chalcophile element contents in the magma do not decrease until water saturation and degassing has occurred. The conservation of chalcophile elements in the magma during magmatic differentiation suggests that most of the magmatic sulfides do not fractionate. By contrast, upon degassing, As, Ag, Au, Cu, Hg, Sb, Sn, Pb, and Zn become depleted in the magma, likely partitioning into the volatile phase, either from the melt or during sulfide oxidation by volatiles. After degassing, the residual chalcophile elements in the melt are incorporated into magnetite. Trace-element data of magnetite enables identifying sulfide saturation during magmatic differentiation and discrimination between pre- and post-degassing magnetite. Our study highlights how magmatic degassing contributes to the metal budget in magmatic-hydrothermal systems that form seafloor massive sulfides and shows that igneous magnetite geochemistry is a powerful tool for tracking metal-mobilizing processes during magmatic differentiation.

The supergene zone of the Cap Garonne mineral deposit (Provence, France) hosts one of the most remarkable mineralogy in the world with no less than 150 minerals, 16 of which are type locality. Such mineral diversity offers a detailed view of mineral and geochemical changes during weathering processes. The stratabound epigenetic primary mineralization occurs within a few meters-thick fluvial conglomerates resting above the Permian–Triassic transition and is probably related to Late Triassic–Early Jurassic hydrothermal events. The Cu–As mineralization in the lower part of the conglomerates is locally overlapped by a thin Pb–Zn-rich layer in the northern mine. The results show that the weathered part is significantly enriched in Cu, Pb, As, Zn, Ag, Ba, Sb, and Bi. The evolution of the supergene fluid is traced in an Eh–pH diagram by the succession of sulfides I (tennantite, galena), sulfides II (covellite), arsenates (olivenite), sulfates and sulfo-arsenates (brochantite, anglesite), and carbonates (malachite, azurite, cerussite). The primary sulfide oxidation acidified the host conglomerate and enabled the crystallization of secondary sulfides and arsenates. Efficient and rapid neutralization by the calcite cement of the host conglomerate and chlorite in the matrix caused successive precipitation of arsenates, sulfates, and carbonates. The supergene processes could be related to major periods of weathering in Western Europe (Early Cretaceous–Late Oligocene/Early Miocene). Erosion-prone periods may have contributed to the stripping of the Pb–Zn-rich layer in the southern mine.

The De’erni Cu–Zn-Co deposit is a typical altered ultramafic-hosted volcanogenic massive sulfide deposit comprising four lenticular main orebodies (0.57 Mt Cu, 1.27% Cu average ore grade; 0.03 Mt Co, 0.09% Co average ore grade; 0.16 Mt Zn, 1.04% Zn average ore grade) hosted in serpentinite and a 200-m-thick basalt was found below the No. I orebody. Serpentinite spinel Al₂O₃, TiO₂, Cr#, and Mg# indicate a mantle-source. Serpentinite magmatic-hydrothermal genesis is indicated by the following: (i) high Rb/Y and Th/Zr ratios, low Nb/Zr ratios, and low δ⁶⁵Cu values; (ii) altered magnetite rims on spinel being characterized by high Cr, Ni, and Ti, and low Ga contents; (iii) pyrite appears along the boundary of spinel grains and has a higher Co and Ni content than pyrite in ores. Therefore, the ultramafic host rocks are formed by strong fluid alteration of primary mantle rocks. The compositional zoning of Co, Cu, and Zn in euhedral coarse-grained pyrite from massive sulfide ore suggests that metal enrichment was associated with three fluid phases, with a clear temporal interval between the fluid activity that introduced Co/Cu enrichment and Zn enrichment (Zn-rich veins in magnetite cross-cut early spinel). Serpentinite exhibits a higher Zn content and decoupling of Ni and Co contents compared to Dur’ngoi ophiolite serpentinite distal from the orebody, implying primary ultramafic rocks may have provided Co to the ores. The apparently high Cu content of the Dur’ngoi ophiolite basalt in comparison with ophiolite basalts worldwide indicates basalt may have supplied the Cu.