Supergene Minerals Research Articles

ПЕРВЫЕ СВЕДЕНИЯ О МЕДНОЙ МИНЕРАЛИЗАЦИИ РУДОПРОЯВЛЕНИЯ ШАРОМСКОЕ, ЦЕНТРАЛЬНАЯ КАМЧАТКА

The report provides new data on the mineralogy of the ores of the Sharomskoye copper ore occurrence, the Kirganik-Sharom ore zone in Central Kamchatka. Copper ores are confined to the central part of the submeridional massif of subalkaline metasomatites. Mineralization is disseminated, less often vein-disseminated in nature.The studied ore samples, collected during field works in 2023, are represented by silicified metasomatites with developed sulfide mineralization. Among the vein and accessory minerals are quartz, chlorite, barite and apatite. Ore minerals are represented by magnetite, chalcopyrite and bornite. Hematite and malachite are the most common supergene minerals, while cuprite and hydroxides of Fe and Cu are less common. The established chalcopyrite-bornite mineral association of the Sharomskoye ore occurrence is considered typical of other copper mineral prospects in central Kamchatka and is characteristic of porphyry copper deposits.

Ore genesis of the Chazangcuo Cu-Pb-Zn deposit in Tibet: evidence from mineralogy, fluid inclusions, S-Pb isotopes, and elemental geochemistry

The Chazangcuo copper-lead-zinc deposit (hereafter referred to as the Chazangcuo deposit) is situated in the northern portion of the western section of the Gangdese polymetallic metallogenic belt in Tibet, with ore bodies strictly governed by Linzizong Group magmatic rocks and EW-trending faults. This study aims to ascertain the mineralization periods, sources of ore-forming materials, metallogenic physicochemical conditions, and genesis of this deposit. Based on comprehensive field geological surveys, sampling, and microscopic examination of petrological and mineralogical characteristics, we perform qualitative and quantitative geochemical analyses of major elements, trace elements, and rare earth elements (REEs), fluid inclusions, and sulfur and lead isotopes. The findings reveal that the mineralization process of the Chazangcuo deposit can be divided into three periods and four stages: the magmatic-hydrothermal, hydrothermal, and supergene mineralization periods sequentially, which consist of the mineralization stages of quartz-pyrite-sphalerite, medium-low-temperature hydrothermal sulfides, chlorite-carbonate minerals, and supergene oxidation in a chronological order. The ore-forming fluids prove to be medium-low-temperature low-density fluids, and the ore-forming materials are characteristic of upper crustal-derived materials. The ore-forming environment is a medium-low mineralization temperature, a shallow and weakly reducing environment. Overall, the Chazangcuo deposit is identified as a medium-low-temperature magmatic-hydrothermal deposit. The metallogenic model has the vertical zoning characteristics of lead-zinc in the upper part and copper in the lower part.

Supergene Oxidized Gold-Silver Deposits in the Americas: Guides for Geologists

Editor’s note: The aim of the Geology and Mining series is to introduce early career professionals and students to various aspects of mineral exploration, development, and mining in order to share the experiences and insight of each author on the myriad of topics involved with the mineral industry and the ways in which geoscientists contribute to each. Abstract Supergene oxidation is a process that has created some of the largest gold and silver orebodies in the Americas, including the Carlin-type (sediment-hosted) gold deposits and Round Mountain in Nevada; Yanacocha and many similar deposits in Peru; Cerro Rico, Bolivia; and Pueblo Viejo, Dominican Republic. Oxidation can make sulfide-bearing gold-silver deposits economic by converting refractory gold-silver–bearing sulfide minerals to minerals that can be leached by dilute cyanide solutions. The use of cyanide heap leaching or tank leaching enabled open-pit mining of low-grade oxidized gold deposits starting in the 1960s. This revolutionized gold mining which, combined with the end of the dollar gold standard in 1971, led to a huge increase in gold production, particularly in the Americas where the technology has been widely applied. During weathering and oxidation of sulfide minerals, particularly pyrite, associated gold and silver form supergene minerals in the oxidation zone but are only transported over short distances (centimeters to meters) due to low solubility of the metals, so they do not form enrichment zones. Gold forms Au0 grains of 1 to 25 µm size and high fineness, as well as invisible gold associated with jarosite and iron oxyhydroxides by sorption or substitution. Silver forms halides and native silver, which may be accompanied by metastable hypogene acanthite. Silver in jarosite, alunite, and Mn oxides is refractory. The economic advantages of near-surface oxidized deposits are that they can be mined by open pit with low costs, commonly not requiring stripping or blasting. Run-of-mine ore is sent directly to leach pads, although some ores may require prior crushing and grinding with agglomeration of fine material such as clays. Oxidized ore is processed by heap leaching using dilute sodium cyanide solution and gold and silver recovered by zinc cementation or on activated carbon. Some ores require grinding and are processed by tank leaching. The hypogene sulfide minerals below the oxidized zone are typically refractory and require at least ultrafine grinding for leaching to be effective, or high-cost oxidation technology for roasting, autoclaving, or bio-oxidation. The sulfide-rich portions of deposits are often not exploited for many decades after discovery, if at all. To explore for supergene oxidized deposits, the exploration geologist requires knowledge of geology, oxide mineralogy, geomorphology, hydrogeology, and the (paleo)-climate, as well as open-pit mining, hydrometallurgy, cyanide leaching, and carbon technology, topics that are introduced here with case studies.

U-Mo-Ba mineralizace na uranovém výskytu Soseň-Kosobody u Jesenice

This paper presents new mineralogical data from the small uranium occurrence Soseň-Kosobody near Jesenice in the Rakovník District in the western part of the Czech Republic. The uranium anomaly, discovered in early 50th, was explored by two shafts No 33 and No 36 in 1954–1959 and subsequently by boreholes and exploration trenches in 1970–1972 (Mrázek 1972). The host rock of the mineralization is Neoproterozioc phyllite of the Teplá-Barrandian Zone or Bohemicum (Fig. 1); the contact with granite and granodiorite of the Čistá-Jesenice Composite Pluton is exposed in the proximity. The studied samples were collected in 2019–2020 and analysed by XRF and ICP-MS for bulk rock chemistry, and by EMPA and XRD for mineralogy (see Table 1 and 2). The samples with primary hydrothermal mineralization were collected in a dump of a shaft No 33(Fig. 2a, b, f), and those with supergene mineralization at a shaft No 36 (Fig. 2c, d). The mineralization occurs in cm thick, discordant brecciated veinlets with sharp contacts (Fig. 3a, b) composed of quartz, K-Ba-feldspar (potassium feldspar to hyalophane), with minor spessartine garnet, pyrite, TiO2 and kaolinite or dickite (Fig. 4a–f). The presence of carbonates and/or baryte mentioned by Mrázek (1972) was not confirmed. The primary mineralization is rather weak and dispersed. An inhomogeneous U-Ca-Pb phosphate phase represents the sole primary uranium carrier. Molybdenum or Mo-S bearing phase forms tiny intergrowths with this phase. Associated ore mineralization is also low-grade, being represented by sphalerite, galena and chalcopyrite (see Figs. 4g–h, Tables 3–5). The samples of supergene mineralization contain common metatorbernite (with minor torbernite) and corkite, accompanied by kaolinite and abundant “limonite” (goethite). The mineralogical and compositional data indicate the origin of mineralization from silica-K-Ba-U-P-Mn-rich fluids poor in sulphate anion. Although the ore mineralization (Pb, Zn, Cu, As and Mo) accompanying uranium is of a low grade, especially the elevated Mo content indicates genetic connection with the Hůrky Mo-REE deposit, which is also associated with the Čistá-Jesenice Composite Pluton (see Klomínský 1962, Kopecký et al. 1997).

Genesis of the Mahour Base Metal Deposit, Iran: Constraints from Fluid Inclusions and Sulfur Isotopes

The Mahour base metal deposit is located northeast of Badroud in the middle of the Urumieh–Dokhtar magmatic arc in the Isfahan province of Iran. The main host rocks to the ores are Eocene volcanic and volcaniclastic rocks. Hypogene ore minerals constituting the main ore body are galena, sphalerite, pyrite, and chalcopyrite. In addition to gangue quartz, a variety of supergene minerals comprising gypsum, goethite, hematite, “limonite”, malachite, azurite, covellite, and chalcocite are also present; gangue minerals are quartz, barite, calcite, sericite, and chlorite. Silicification, intermediate argillic, and propylitic are the main wall-rock alteration types. The presence of fluid inclusions with different vapor/liquid ratios in quartz and sphalerite could indicate a boiling process. The primary liquid-rich fluid inclusions suggest that the homogenization temperature was between 107 and 298 °C from fluids with salinities from 1.5 to 13.7 wt.% NaCl equiv. These data suggest that the ore-forming fluids were magmatic with a contribution from meteoric waters. The δ34S values of sulfides range from 1.9 to 3.4‰, those of barite range from 12.1 to 13.2‰, and those of gypsum range from 4.3 to 5.6‰. These data suggest that sulfur was mostly of magmatic origin with a minor contribution from sedimentary rocks. Our data suggest that the boiling of fluids formed an intermediate-sulfidation style of epithermal mineralization for the Mahour deposit.

Correction to: Tracing the Eh–pH evolution of Cu–Pb–As–Zn supergene mineralization using detailed petrography in the Cap Garonne mineral deposit (Provence, France)

Correction to: Tracing the Eh–pH evolution of Cu–Pb–As–Zn supergene mineralization using detailed petrography in the Cap Garonne mineral deposit (Provence, France)

Tracing the Eh–pH evolution of Cu–Pb–As–Zn supergene mineralization using detailed petrography in the Cap Garonne mineral deposit (Provence, France)

Tracing the Eh–pH evolution of Cu–Pb–As–Zn supergene mineralization using detailed petrography in the Cap Garonne mineral deposit (Provence, France)

Metallogenic model of the Amensif Zn-Pb-Cu-Ag±Au-Bi carbonate replacement deposit (Western High Atlas, Morocco): New litho-structural and mineralogical data

Purpose. In this paper, we discuss the genetic model and emphasize many pending issues on the carbonate replacement textures of the Amensif Zn-Pb-Cu-Ag±Au-Bi deposit (the Western High Atlas, Morocco), the source of metal and the possible contribution of the Azegour granite to this ore genesis. Methods. This study is based on geological mapping, drill core and petrography analysis in combination with ICP-AES, XRD, and SEM data. Findings. The detailed mineralogy consists mainly of sulfides and sulfosalts. The main ore minerals include arsenopyrite, pyrite, sphalerite, chalcopyrite, galena and bismuthinite. Mineral inclusions related to isomorphic sulfosalts are found in galena and/or chalcopyrite. They include matildite, galenobismutite, pavonite, cosalite, schirmerite, krupkaite, ramdohrite, wittichenite, emplectite, luzonite, gustavite, hedleyite, krennerite, wittite, freibergite, tetrahedrite, tennantite and native bismuth. The supergene minerals are anglesite, covellite, malachite, azurite and goethite. In addition, specific replacements are observed between dolomites and sulfides, indicating an interaction between hydrothermal fluid and host rocks. Four ore stages have been identified based on the relationship between mineral phases and ore-forming conditions. The results of this study indicate that Ag and Au precipitation is controlled by the Bi-Te-Pb-S system, while enrichment in Bi, Te and Se sulfosalts and Bi-telluride indicates a magmatic source of the ore-forming fluid. Originality. The study delves into the genetic model of the Amensif Zn-Pb-Cu-Ag±Au-Bi deposit in the Western High Atlas, Moroc-co, with a focus on carbonate replacement textures, while also exploring its classification as either a carbonate replacement deposit or a skarn deposit. Practical implications.Mineral textures are indicators of the replacement process in the Amensif Zn-Pb-Cu-Bi-Ag±Au carbonate replacement deposit (the Western High Atlas, Morocco). The results obtained from this research paper can be used as a powerful tool in mineral exploration of the Western High Atlas.

The application of PRISMA hyperspectral satellite imagery in the delineation of distinct hydrothermal alteration zones in the Chilean Andes: The Marimaca IOCG and the Río Blanco-Los Bronces Cu-Mo porphyry districts

This study provides an overview of the application of hyperspectral imagery acquired by the Italian satellite mission “PRecursore IperSpettrale della Missione Applicativa” (PRISMA), for mapping hydrothermal and supergene mineral alteration zones associated with different Cu deposits in the Chilean Andes. Study areas include the Marimaca Copper Project in the Naguayán district (Antofagasta Province), hosting Late Jurassic – Early Cretaceous iron oxide-copper–gold mineralizations and the Río Blanco-Los Bronces district (Santiago Region) known for its Late Miocene – Early Pliocene copper-molybdenum porphyry deposits. These mineral systems exhibit hydrothermal alteration haloes extending over several kilometers, with upward and outward mineral zonation.To characterize the surface-exposed alteration, the satellite imagery was processed using a multiple feature extraction workflow targeting the relative abundances and compositions of specific supergene and hydrothermal alteration minerals, including Fe-oxides and hydroxides (hematite-goethite), phyllosilicates (micas-kaolinite-chlorite), hydroxyl-bearing sulfates (alunite-natroalunite-jarosite) and epidote. The results reveal a zonation from proximal sulfates (natroalunite to alunite) and Al-rich white mica (ranging from 0.3 km-wide for the area identified to the east of the Marimaca deposit to 1 km-wide in correspondence of the Los Sulfatos deposit, respectively) to distal Al-poor white mica (0.2 to 0.5 km-wide, respectively) and an outer chlorite-epidote zone. In the Marimaca Project area, the structurally-controlled alteration evolves west to east from chlorite-rich to phengitic white mica (Al-poor). A NNE-SSW trending supergene leached cap covers a 6 km-long and up to 2 km-wide area from north to south. Our study documents how spaceborne hyperspectral imaging spectroscopy can support mineral exploration by enabling non-invasive reconnaissance mapping of the outcropping rocks, providing specific targeting information for follow-up field surveys and drilling campaigns.

Supergene mineral assemblage from sediments affected by contact and hydrothermal metamorphism, locality Dobrá – Staré Město near Frýdek-Místek (Czech Republic)

At locality Dobrá – Staré Město, series of outcrops occur on both banks of the Morávka River. The river cuts through the sediments on the tectonic contact between the Silesian and Subsilesian units of the Outer Western Carpathians. Clayey facies of the Hradiště Formation (Early Cretaceous, Valanginian to Aptian) contains numerous tectonic fragments reaching hundreds meters in size of strongly altered (carbonatized, smectitized) subaquatic volcanic rocks of the Teschenite Association. These volcanic rocks are dominated by fine-grained to aphanitic rocks, possibly of both effusive and intrusive origin. The host sediments affected by the contact metamorphism (contact adinole) also occur. Framboidal pyrite is abundant in majority of sediments of the studied area, giving rise to efflorescences of gypsum, baryte, celestine, and a mineral of alunite group (Figure 1). A more varied assemblage of supergene minerals was recognized on a small rock outcrop at GPS coordinates N 49° 39.992’ E 018° 23.810’ (Figure 2), where it developed relatively recently after the big floods in 2010 that washed away the previous mineralization. During the first years, only gypsum crusts were detectable, while in 2023, we recognized 4 macroscopic and 5 microscopic minerals forming thin botryoidal crusts. These crusts show faint zoning, with gooey, gel-like X-ray amorphous material in the humid upper part , middle zone with abundant fibroferrite and the lower part dominated by gypsum. Gypsum forms well-developed, but frequently corroded crystals with various habitus (Figure 4A, B). Fibroferrite is present as fibrous aggregates with individual crystals of up to ca. 100–150 µm long and <1 µm thick (Figure 4C). It forms directly from the gel-like substance (Figure 4D). Rhombohedral crystals and rossete aggregates of hydroniumjarosite vary from 2 µm to 5 µm in size (Figure 4E), but the most common are dust-like coatings on rock fissures with particle size <1 µm. Rusty coatings of schwertmannite (Figure 4F), in some places accompanied by gypsum, with Fe/S at. % ratios near 4–5 are common. In some cases, the Al/Fe at. % ratio exceed 1, which might indicate presence of yet undescribed Al-analogue of schwertmannite, ill-defined alumogel, or an amorphous precursor of aluminite. Presence of ferrihydrite is possible but not confirmed. The above-mentioned Fe-rich phases are frequently accompanied by diplobacilli-shaped bacteria (Figure 4F). Slavíkite, pickeringite-halotrichite, alunogen, copiapite group mineral, hexahydrite, and melanterite (Figure 5) were also recognized by EDS and PXRD. Slavíkite and copiapite group minerals seem to be alteration products of fibroferrite. Unit-cell parameters refined from the X-ray powder diffraction are presented for all recognized phases (Table 1). Surprisingly, secondary sulfates are present on the metasediments with abundant calcite (Figure 3), which should serve as a neutralization buffer. The reason is the restricted amount of calcite available on the rock fissure surfaces, and water infiltration partially blocked by newly-formed gypsum. The albite in contact adinole (Figure 3) is unaffected by the acid rock drainage, since Na ions are not present in significant quantities in supergene phases. Since there is still enough available unaltered pyrite, we expect a shift towards more stable mineral assemblage in future. The limited amount of secondary sulfates does not present any significant harm to the environment.

Gersdorffit, tyrolit a Bi-minerály z žilné Cu mineralizace z lomu Smrčník u Lipové-lázní u Jeseníku (Česká republika)

A previously unknown primary Ni-As-Bi and supergene As-Bi mineralization was found in the active marble quarry Smrčník located 2 km WNW of the village of Lipová-Lázně, 7 km WNW of Jeseník, Rychlebské hory Mountains, Czech Republic. An electron-microprobe study of newly collected samples from a weakly Cu-mineralized quartz-carbonate vein cutting the marbles showed the presence of gersdorffite, bismuthinite, an unidentified Cu-Bi sulphide, bismite, and tyrolite, which were not known from the wider area. The microscopic grains of gersdorffite are part of primary ore mineralization of the studied vein with prevailing chalcopyrite, which is in places rimmed by chalcocite and djurleite. Nickel is partly replaced especially by Co (0.002 - 0.246 apfu) and Fe (0.030 - 0.158 apfu), less by Cu (0.008 - 0.038 apfu), whereas arsenic is weakly substituted by Sb (0.008 - 0.083 apfu) and in part of collected analyses by Bi (0.001 - 0.033 apfu) in the studied gersdorffite. All mentioned Bi minerals hosted by chalcopyrite were recorded in a single aggregate only. The blue-green tyrolite is a rare compound of supergene mineral assemblage of the same vein. Its chemical composition is characterized by small contents of S (0.050 - 0.248 apfu), P (0.052 - 0.104 apfu), and mostly also Cl (0.022 - 0.070 apfu). The new findings suggest much richer mineralogical and chemical variability of primary (hypogene) mineralization of hydrothermal veins, than was indicated by previous studies in the wider area.

Genesis of sediment‐hosted copper and silver mineralization at the Omatapati prospect, Kaoko Belt, Opuwo district, Kunene region, Namibia

AbstractThe Omatapati copper and silver prospect within the Kaoko Belt is located in the Opuwo district, Kunene region, Namibia. The prospect is hosted by dolomite and interbedded argillites of the Neoproterozoic Devede Formation, the Ombombo Subgroup. An ore body is exposed in shallow artisanal mining pits and drill‐cores of the prospect have grades of 0.4 to 5.2 wt% Cu, and 23 to 312 g/t Ag. The prospect was formed by both hypogene and supergene mineralization processes. The hypogene mineralization occurred in three stages. Stage 1 is represented by calcite veins containing chalcopyrite, bornite, sphalerite and galena. Stage 2 consists of quartz and calcite veins with chalcopyrite and bornite. Stage 3 consists of quartz‐calcite‐barite veins with chalcopyrite. The veins of stages 1 and 2 are subparallel or discordant to the foliation of argillites, and those of Stage 3 are NE‐striking and steeply dipping in the brecciated dolostone and argillite. The mineralization stages 1, 2, and 3 are overprinted by supergene chalcocite, digenite, annite, covellite, malachite, delafossite, hematite, and goethite. The supergene process forms a semi‐massive chalcocite‐covellite zone, which extends from the surface to ~50 m depth. The veins show average concentrations of 2.1 wt% Cu, 80 ppm Ag, and 532 ppm Pb for the stage 1, 3.1 wt% Cu, 118 ppm Ag, and 66 ppm Pb for the stage 2, and 18.6 wt% Cu, 675 ppm Ag, and 565 ppm Pb for the Stage 3 with supergene overprinting. Silver occurs as impurity in supergene chalcocite (6303 ppm Ag), digenite (4425 ppm Ag), and covellite (3060 ppm Ag). Fluid inclusions in quartz and calcite revealed that the hypogene mineralization occurred under a pressure >7–8 MPa. Temperatures of ore formation of the stages 1, 2, and 3 were >145–155 °C, >290–300 °C, and >190–230 °C, respectively. Large variation of salinities in each fluid inclusion assemblage suggests fluid mixing and dilution processes. Fluid inclusion gas compositions in the Stage 3 have weighted means of 98.98 mol% H2O, 0.75 mol% N2, 0.52 mol% CO2, 0.02 mol% CH4, 0.0021 mol% Ar, 0.0009 mol% H2S, and 0.00006 mol% He and indicate a signature of magmatic fluids mixed with meteoric waters or seawater. δ34SCDT values of sulfides in the stages 1, 2, and 3 in the prospect have three data clusters, (1) near 0 ‰ of chalcopyrite in the stages 1 and 2, (2) near −11 ‰ of bornite in the stage 2, and (3) +5 to +11 ‰ of the supergene chalcocite and covellite. Modes of occurrence of ores, fluid inclusions and sulfur isotope data show that the prospect is likely the same type as sediment‐hosted copper‐silver deposits with veining found in the Central African Copperbelt.

Genesis and supergene weathering of tetrahedrite-(Hg) in meta-carbonate rocks: Bearing on differential mobility of priority pollutant metals

The Cu-Sb-Hg mineralization of San Giuliano Terme (Monti Pisani, Tuscany, Italy) is characterized by the widespread occurrence of deeply altered tetrahedrite-(Hg) hosted within joints and faults in the Liassic “Calcari ceroidi” Formation. Through a multi-technique approach (optical and scanning electron microscopy, electron microprobe analysis, single-crystal and powder X-ray diffraction, micro-Raman spectroscopy, X-ray fluorescence, fluid inclusion analysis), tetrahedrite-(Hg) and its alteration products have been characterized and data about its genesis and successive supergene weathering have been collected. Tetrahedrite-(Hg) from San Giuliano Terme has the empirical formula Cu9.92Ag0.02(Hg1.64Fe0.30Zn0.04)Σ1.98(Sb3.53As0.56)Σ4.09S12.95, and is found with scarce gangue minerals represented by calcite, baryte, and very rare fluorite. The mineralization formed from hydrothermal fluids with moderately high salinity (∼17.5 wt% NaClequiv.) of dominantly metamorphic origin at T ∼ 285 °C. Tetrahedrite-(Hg) is usually fully replaced by a mixture of cinnabar, roméite-group minerals, malachite, and rarely azurite. Based on the modal abundance of the mineralogical constituents and their micro-textures, four stages of supergene weathering of tetrahedrite-(Hg) have been recognized. The alteration stages reflect the progressive ingression of meteoric water into the system, with consequent oxidation of tetrahedrite-(Hg) and the introduction of Ca2+, HCO3– and H2O, as well as the progressive removal of S, Sb, and Cu. The relative proportions of the supergene minerals in the four alteration stages can be taken as a proxy for the mobility of the main chemical constituents of tetrahedrite-(Hg), three of which (Hg, Sb, and Cu) are priority pollutant metals. Mercury was found to be the least mobile element in the reconstructed geochemical process. In fact, the widespread precipitation of cinnabar in the space formerly occupied by tetrahedrite-(Hg) hinders the dispersion of Hg in the environment, sequestering it in a solid matrix.

Ore-Forming Fluids of Orogenic Gold Deposit In Tamilouw-Haya, Seram Island, Indonesia

The Tamilouw-Haya orogenic gold deposit is located in the southern arm of Seram Island, Indonesia, occupying Tehoru Metamorphic Complex. Gold mineralization is predominantly in the form of veins, stockwork, and breccia, although minor dissemination is slightly appeared in the rock float samples. Ore-mineral assemblages are dominated by native gold, pyrite, chalcopyrite, sphalerite, tetrahedrite-tennantite (sulfosalt), galena, pyrrhotite, marcasite, realgar, kalininite, and arsenopyrite. Covellite, hematite, goethite, and malachite appear as supergene minerals. High-grade gold ores in this area are generally found in quartz-carbonate veins with the main alteration processes involving silicification, carbonatization, and sericitic. The P-T history of the mineralization was revealed by fluid inclusions, and this study implies the depth of ore deposit and its evolution during mineralization. The primary fluid inclusions from three different types of quartz/quartz-carbonate veins in Tamilouw-Haya crystallized at the homogenization temperature (Th) of 240 °C to 340 °C, with a fluid salinity from 3.87 to 0.70 wt. % NaCl equivalent, and melting temperature (Tm) of -0.4 to -2.3 oC. The ore-forming fluids consist mainly of two-phase (VCO2+LH2O) liquid-rich aqueous inclusions, characterized by low to rich CO2, low salinity, and moderate temperature. There are three vein types as the ore-bearing fluids with precious metals and anomalous high basemetal contents. Quartz type 1- veins (V1); concordant veins, formed at a temperature of 240-307 oC with an average salinity of 1.8 wt. % NaCl equivalent. Quartz type 2- veins (V2) tend to cut the rock foliation which are formed at temperature range from 293-336 oC with the average salinity that shows a value of 2.4 wt. % NaCl equivalent. Meanwhile, type 3 quartz-carbonate veins (V3) are formed at the temperature range of 240-340 oC and the average salinity of 2.72 wt. % NaCl equivalent. These quartz-carbonate veins cut the wall-rock foliation, which is identified as the late stage and associated with ore deposition in Tamilouw-Haya. The gold deposit in Tamilouw-Haya is formed at a depth of about 5.5-9 km of paleosurface, and the pressure between 1.7-2.4 Kbar in epizonal to mesozonal zones. Keywords: Tamilouw-Haya, orogenic gold, fluid inclusion, microthermometry, ore-forming fluids

Genesis of Hg-Sb deposit controlled by strike-slip structures in Qinling orogenic belt: A case study of the Qingtonggou ore deposit, Shaanxi, China

The Qingtonggou deposit is the largest Hg-Sb deposit in the Qinling orogenic belt, but the deposit genesis remains unclear. Fluid inclusion study indicates that the homogenization temperature range from 139.9 °C to 217 °C and the salinities vary from 0.7 to 2.1 wt% (NaCleq). The δ13C value in ore-stage calcite is from-7.6 ‰ to −7.1 ‰, and the δ18OSMOW value is between 13.6 ‰ and 15.3 ‰. The δ18OV-SMOW value in hydrothermal quartz is from 21.5 ‰ to 24.8 ‰, and the δD value is between −138 ‰ to −99 ‰. The δ34SV-CDT value range from 4 ‰ to 11.6 ‰, the 206Pb/204Pb values range from 18.0351 to 18.5080, the 207Pb/204Pb values range from 15.6390 to 15.6672, and the 208Pb/204Pb values range from 38.1586 to 38.4128. The hydrothermal calcite Sm-Nd isochron age for ore-stage calcite is 98.02 ± 0.42 Ma. The Hg-Sb mineralization is controlled by tectonic space formed by the left strike-slip fault, the ore-forming fluid has the characteristics of medium–low temperature, low density, and supergene mineralization, the ore-forming fluid comes from meteoric water and formation water, the ore-forming material comes from the stratum and basement of Yaolinghe group and Lower Cambrian, the Hg-Sb mineralization occurred at early Late Cretaceous. The complete metallogenic process is that the Yaolinghe Group and Lower Cambrian in this area are the source areas for Hg-Sb mineralization, the subsequent high background values Hg and Sb strata which received the denudation deposit of the source bed all contributed ore-forming materials, with the Qinling collision orogeny and extrusion in the Indosinian period and the continuous contraction of the Paleozoic basin, porous meteoric water and formation water extracted the ore-forming materials in source bed, formed ore-forming fluids, during the strike-slip process in intracontinental environment, deep and large faults provide a channel for the upward discharge of ore-forming fluids, with the decrease of fluid temperature, sulfide precipitation occurs in secondary fracture.

Discovery of supergene REE-fluorocarbonate minerals in weathered spheres of Xiajialing regolith-hosted rare earth element deposit in Xiangshan, Jiangxi Province, South China

The Xiangshan ore field is developing not only a volcanic-related hydrothermal U deposit, but also a regolith-hosted rare earth elements (REE) deposit in the middle of the volcanic rock basin, where the spheroidal weathering layer has the highest REE content. Weathered spheres may play an important role in REE mineralization. To explore the enrichment and migration processes of REE in weathered spheres at different weathering stages, the mineralogy and geochemistry of the bedrock and weathered spheres with different weathering degrees of Xiajialing REE deposits were investigated. Results showed that the REE+Y concentration was 270–310 ppm in bedrock and 372–2377 ppm in weathered spheres, respectively. With an increase in weathering, the REE+Y content increased and then decreased, and the maximum value was observed in the core of the moderately weathered sphere sample. A large number of supergene REE-fluorocarbonate minerals were discovered in the weathered spheres (particularly in samples with a high REE content), and were mainly distributed in biotite and plagioclase. The REE2O3 (including Y2O3) content of the supergene REE minerals was 69.04–80.89 wt%. The supergene REE minerals were enriched in La2O3 (21.69–25.95 wt%), Nd2O3 (12.13–23.58 wt%), and Y2O3 (2.74–14.27 wt%), but lacked Ce2O3 (<1 wt%), and contained a certain amount of F (2.66–6.23 wt%). The Raman spectra of the supergene REE-fluorocarbonate showed several bands at 272, 741, 1103, and 3100–3700 cm−1. These results indicate that REE are adsorbed on clay minerals that were formed by weathering of biotite and plagioclase; thus, the concentrations of REE around the clays were extremely high and may have exceeded the solubility product (Ksp) of the REE-fluorocarbonate, which contributed to the supergene REE-fluorocarbonate deposits. The formation of supergene REE-fluorocarbonate minerals may be one of the most important causes of the extreme enrichment of REE in some weathered sphere samples. However, the supergene mineral is easily weathered and would dissolved with weathering proceeding, leading to a decrease in the REE content in the sphere samples that have experienced relatively strong weathering. The supergene REE-fluorocarbonate may be an important intermediate product in the formation of the Xijialing regolith-hosted REE deposit.

Genesis and Evolution of the Yolindi Cu-Fe Skarn Deposit in the Biga Peninsula (NW Turkey): Insights from Genetic Relationships with Calc-Alkaline Magmatic Activity

The current work investigates the impact of magmatic fluids and metasomatic processes on the Yolindi Cu-Fe skarn deposit in the Biga Peninsula, Turkey. It traces the stages of skarn evolution, from prograde to retrograde alterations, and investigates findings within a broader geological, mineralogical, and geochemical framework. Additionally, it assesses the evolutionary history of the Yolindi deposit in relation to calc-alkaline magmatic activity in an island-arc environment and compares its mineral compositions and genesis with other global and regional Cu-Fe skarn deposits. The Yolindi Cu-Fe skarn deposit in the Biga Peninsula was formed by the intrusion of Şaroluk quartz monzonite pluton into Upper Paleozoic Torasan Formation rocks such as phyllite, schists, hornfels, marble, and serpentinites. During skarnification, reactions between the magmatic fluids from the Şaroluk quartz monzonite pluton and the Torasan Formation produced skarn minerals associated with metals such as Fe and Cu. Initially, these reactions formed prograde skarn minerals such as augite-rich pyroxenes and andradite garnets with magnetite and pyrite. As the system cooled, these initial minerals underwent retrograde alteration, leading to the formation of minerals such as epidote, actinolite, and chlorite, as well as other copper and iron minerals including chalcopyrite, bornite, secondary magnetite, and specular hematite. Therefore, four main stages influenced the formation of the Yolindi Cu-Fe deposit: metamorphic bimetasomatic, prograde metasomatic, and retrograde metasomatic stages. Later, oxidation and weathering resulted in supergene minerals such as cerussite, malachite, and goethite, which serve as examples of the post-metamorphic stage. The mineralogical shifts, such as the andradite–grossular transition, reflect changing hydrothermal fluid compositions and characteristics due to the addition of meteoric fluids. Importantly, the formation of magnetite after garnet and clinopyroxene during the retrograde stage is evidenced by magnetite crystals within garnet. The mineral associations of the Yolindi Cu-Fe skarn deposit align with the global skarn deposits and specific Turkish skarns (e.g., Ayazmant Fe-Cu and Evciler Cu-Au skarn deposits). The Yolindi Cu-Fe skarn deposit, in association with ore-bearing solutions having magmatic origins, developed in an island-arc setting.

Secondary uranyl arsenates–phosphates and Sb–Bi-rich minerals of the segnitite–philipsbornite series in the oxidation zone at the Prakovce-Zimná Voda REE–U–Au quartz-vein mineralisation, Western Carpathians, Slovakia

AbstractThis work is an investigation of the assemblages of supergene minerals occurring in hydrothermal REE–U–Au quartz-vein mineralisation at the Prakovce-Zimná Voda site, Slovakia. Heterogeneous uranyl arsenates and minor phosphates of the autunite group (nováčekite, kahlerite, threadgoldite, autunite, arsenuranospathite and chistyakovaite) together with scorodite and Sb–Bi-rich philipsbornite–segnitite-series minerals formed by oxidising fluids during decomposition and leaching of primary hypogene uraninite, brannerite and base-metal sulfides and sulfosalts. A progressive change of pH from acidic to near-neutral due to the gradual consumption of sulfides resulted in the formation of late phosphuranylite, pharmacosiderite and arseniosiderite. Goethite and other Fe oxides represent the latest hydrous ferric mineral phases and were formed after most of the As was already fixed in Fe arsenates. Antimony and Bi were taken up only into philipsbornite–segnitite and suggest unusual conditions during this process. X-ray absorption spectroscopy indicates that Sb in the philipsbornite–segnitite is fully oxidised (0.1–0.4 apfu Sb5+, octahedral coordination on the G site). Pentavalent Sb together with the presence of ferric oxides and arsenates and uranyl minerals suggest oxidative conditions during weathering. This study also indicates that hydrous ferric arsenates are dominant and stable secondary minerals in a supergene environment in a quartz vein rich in Fe and As accompanied by elevated concentrations of U, Pb, Sb, Bi, S, P, Ca and Ba under oxidising conditions.

Re-examination of the Aïn Allegua-Aguiba celestite-Pb-Zn salt diapir-related Mississippi Valley-type deposits (Nappes zone, Northwestern Tunisia): New conceptual model

The celestite-rich and Pb-Zn-poor Aïn Allegua deposits are located at the northeastern extremity of the Dougas diapir in the Nappes zone of northern Tunisia. The Sr-Ba-Zn-Pb mineral system studied in this paper is enclosed in a Triassic breccia, labeled cap rock, located between the Triassic diapir and the surrounding Cretaceous to Lutetian marine sediments. It consists of evaporite dissolution float breccia where Triassic dolostone clasts are floating in a Triassic matrix of anhydrite and argillites. Five mineralizing stages are recognized, which are from early to late: celestite (stage 1); hydrothermal dolomite (stage 2); crosscutting galena-barite or sphalerite-galena-barite-calcite (stage 3); (4) fracture and karst filled by barite, celestite, and galena (stage 4); and late supergene mineralization (strontianite, smithsonite, and cerussite) (stage 5). The present study shows that the celestite and Pb-Zn mineralization formed from the circulation in the cap rock of at least three fluids: (1) fluid A (100–150 °C; 10 to 25 wt% NaCl eq.) deposited the celestite; (2) fluid B (125 to 185 °C; 29 to 34 wt% NaCl eq.) deposited the hydrothermal dolomite, and (3) fluid C (temperatures around 90 °C; 14 to 22 wt% NaCl eq.) deposited the calcite that accompanied sphalerite and galena precipitation. The δ34S values for sphalerite and galena fall within a narrow range from + 10.4‰ to + 18.9‰ (avr. 13‰) indicating a homogeneous source of sulfur. The δ34S values of celestite and barite are also relatively homogeneous from + 14.7 to + 23‰ (ave. + 16.5‰) and match those of Tunisian Triassic gypsum and Triassic marine sulfates (δ34S = +15‰). The temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of Triassic sulfate. The lead isotopes in galena show that Pb, and probably Zn and Ba were extracted from the upper crustal rocks. Part of the strontium is derived from the Triassic anhydrite and the other part is probably transported to the cap rock in formation waters. The tectonic setting, the carbonated nature of the host rocks, the epigenetic style of the mineralization, and the mineral associations, together with fluid inclusions data and sulfur and lead isotopes show that the Aïn Allegua deposit belongs to the diapir-related Mississippi Valley-type (MVT) deposits of the Eastern Maghreb salt diapirs province, that formed, as the most of the MVT deposits and districts in the world, from basinal brines with no mixing with metamorphic and/or magmatic fluid or involvement of a heat source from a concealed sill or magmatic intrusion.

Mallestigite, Pb3Sb(SO4)(AsO4)(OH)6·3H2O, from the type locality – new data, crystal structure, and structural relationships

A report of the supergene mineral mallestigite, Pb3Sb5+(SO4)(AsO4)(OH)6·3H2O, from the type locality Neufinkenstein-Grabanz district, Mallestiger Mittagskogel, Carinthia, Austria, is given in order to close gaps that have been left open since its first description. At the type locality, the dump of an abandoned small copper-lead-zinc mine, the mineral occurs frequently in up to ⁓2 mm long clear colourless idiomorphic hexagonal prisms {100} terminated by the bipyramid {101}. Details of the occurrence, paragenesis, physical properties, a FTIR spectrum and X-ray powder diffraction data are reported. Chemical analysis in a scanning electron microscope in conjunction with a crystal structure analysis gave the empirical formula Pb3.02Sb1.06(SO4)0.96(AsO4)0.97(OH)6·3H2O. An ab-initio crystal structure determination with CCD diffractometer data, MoKα radiation, and a nearly untwinned crystal proved that mallestigite is hexagonal, space group P63, a = 8.9326(4), c = 11.1044(5) Å, V = 767.33(8) Å3, Z = 2, and gave a final R1 = 0.0184 for 1632 independent reflections with I > 2σ(I). Mallestigite belongs to the fleischerite group. The structure is built up from [Sb5+(OH)6]1– octahedra which are linked by triplets of edge-sharing Pb2+ into chains [Pb3Sb(OH)6]5+ extending along a 63 axis. Each three of such chains are bridged by triplets of H2O and by rows of SO42– and AsO43– tetrahedra alternating along a 3-fold axis and showing very different links to the Pb atom. Pb2+ is in a strongly distorted one-sided [9]-coordination by O atoms that makes the structure clearly hemimorphic. Structural relationships to the fleischerite group minerals schaurteite, genplesite, despujolsite and fleischerite as well as to synthetic Ba3Sn4+(SeO4)2(OH)6·3H2O are outlined and changes in the space group symmetry of despujolsite (P6¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline6$$\\end{document}2c → P63/mmc) and fleischerite (P6¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline6$$\\end{document}2c → P63) are proposed.