Mineralogy and distribution of critical elements in the Sn–W–Pb–Ag–Zn Huanuni deposit, Bolivia

The polymetallic Huanuni deposit, a world-class tin deposit, is part of the Bolivian tin belt. As a likely case for a “mesothermal” or transitional deposit between epithermal and porphyry Sn types (or shallow porphyry Sn), it represents a case that contributes significantly to the systematic study of the distribution of critical elements within the “family” of Bolivian tin deposits. In addition to Sn, Zn and Ag, further economic interest in the area resides in its potential in critical elements such as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Huanuni deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approach. With In concentrations consistently over 2000 ppm, the highest potential for relevant concentrations in this metal resides in widespread tin minerals (cassiterite and stannite) and sphalerite. Hypogene alteration assemblages are hardly developed due to the metasedimentary nature of host rocks, but the occurrence of potassium feldspar, schorl, pyrophyllite and dickite as vein material stand for potassic to phyllic or advanced argillic alteration assemblages and relatively high-temperature (and low pH) mineralising fluids. District-scale mineralogical zonation suggests a thermal zonation with decreasing temperatures from the central to the peripheral areas. A district-scale zonation has been also determined for d34SVCDT values, which range -7.2‰ to 0.2‰ (mostly -7‰ to -5‰) in the central area and -4.2‰ to 1.0‰ (mainly constrained between -2‰ and 1‰) in peripheral areas. Such values stand for magmatic and metasedimentary sources for sulfur, and their spatial zoning may be related to differential reactivity between mineralising fluids and host rocks, outwardly decreasing from the central to the peripheral areasPeer ReviewedPostprint (published version

Remobilization of Ni–Co–As and platinum-group elements by carbonate metasomatic alteration (listvenitization) of metaultramafic rocks from Dobšiná, Slovakia

Hydrothermal processes are mainly responsible for the release and accumulation of metals and metalloids in rocks. In this work, we investigated the mineralogy and geochemistry of altered metaultramafic rocks (listvenites) that are spatially associated with Ni–Co ores near Dobšiná aiming to identify the sources of the elements in the hydrothermal Ni–Co-mineralization. Optical microscopy, electron microprobe analysis, and laser-ablation inductively coupled mass spectrometry were used to correlate the mineralogy with the degree of rock alteration. The sulfides and silicates in the meta-ultramafic rocks host rare, tiny inclusions of cooperite (nominally PtS), sperrylite (PtAs2), Pty–Pd–Ir–Te phase, and Pt–Au–Cr-alloy. The results show that the metaultramafic rocks were the source of Ni and Co and that platinum-group elements (PGE) were also leached and mobilized from the metaultramafic rocks. LA-ICP-MS scans show that the sulfarsenides in the metaultramafic rocks host submicrometer inclusions of PGE minerals but the hydrothermal Ni–Co sulfarsenides contain much less PGE’s. These observations document the limited mobility of the PGE‘s. Changes in the sulfide mineralogy as a function of degree of alteration suggest that the fluids brought Fe and S, and probably a substantial amount of As whereas the metaultramafic rocks supplied Ni, Co, PGE, and perhaps also some As

Les minéralisations Cu-(Ni-Bi-U-Au-Ag) d'Ifri (district du haut Seksaoua, Maroc) : apport de l'étude texturale au débat syngenèse versus épigenèse. <br /> The Cu---(Ni---Bi---U---Au---Ag) mineralization of Ifri (‘Haut Seksaoua' district, Morocco): contribution of a textural study to the discussion syngenetic versus epigenetic

The Cu ore of Ifri is a chalcopyrite stockwork hosted by Cambrian formations and was until now interpreted as a syngenetic massive sulphide deposit. Textural studies highlight two generations of pyrite early (Py I) and late (Py II) with respect to the regional deformation. The chalcopyrite stockwork overprinted Py II, outlining the epigenetic nature of the Cu mineralization. Regarding the origin of Cu-depositing fluids, the presence in the stockwork paragenesis of an U, W, Sn association and preliminary Pb/Pb dating of a brannerite belonging to this association suggest a contribution of the Tichka granite

Spatial and metallogenic relationships between different hydrothermal vein systems in the Southern Arburèse district (SW Sardinia)

The SW Sardinian basement hosts various ore deposits linked to geological processes active from Cambrian to post-Variscan times. In particular, the Southern Arburèse district hosts several granite-related W-Sn-Mo deposits and a 10 km-long system of Ni-Co-As-Bi-Ag±Au-bearing five-element veins. New investigations in the eastern and central parts of the district (Pira Inferida mine sector) were performed to understand the poorly documented spatial and metallogenic relationships between these systems. The granite-related deposits consist of massive wolframite quartz (W-Bi-Te-Au) and molybdenite-quartz veins, linked to the early Permian (289±1 Ma) Mt. Linas granite, that are cross-cut by the five-element veins. The wolframite-quartz veins, observed by optical and electron (SEM-EDS) microscopy, show abundant native Bi, Bi-Te phases and native Au suggesting a W-Bi-Te-Au hydrothermal system. The five-elements veins exhibit breccia and cockade textures enveloping clasts of the Ordovician host-rocks and locally small fragments of the earlier W-Mo-quartz veins. The five-element vein paragenesis includes three main stages, from older to younger: 1) native elements (Bi±Au); 2) Ni-Co arsenides-sulfarsenides in quartz gangue; and 3) Pb-Zn-Cu±Ag sulfides in siderite gangue. The mineralogical, geochemical and isotopic features of the five-element vein swarm are closely comparable to five-element deposits elsewhere in Europe (Germany, Switzerland, Italian Alps). While the source of Ni and Co is still unknown, the high Bi contents as well as Au enrichment in the five-element veins suggest selective remobilization of these elements, and perhaps others, from the granite-related W-Bi-Te-Au veins. The five-element vein system was likely formed during a post-289±1 Ma and post-Variscan metallogenic event

Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy

We compare three poorly known, historical Ni–Co-bearing hydrothermal deposits in dierent geological settings in Italy: The Ni–Co–As–Sb–Au-bearing Arburese vein system (SW Sardinia), the Co–Ni–As-rich Usseglio vein system (Piedmont), and the small Cu–Ag–Co–Ni–Pb–Te–Se stockwork at Piazza (Liguria). These deposits share various (mineralogical, chemical, thermal, and stable isotopic) similarities to the Five Element Vein-type ores but only the first two were economic for Co–Ni. The Sardinian Ni-rich veins occur in Paleozoic basement near two Variscan plutons. Like the Co-rich Usseglio vein system, the uneconomic Piazza deposit is hosted in an ophiolite setting anomalous for Co. The Sardinian and Usseglio deposits share a polyphasic assemblage with Ni–Co–As–Sb–Bi followed by Ag-base metal sulfides, in siderite-rich gangue, whereas Piazza shows As-free, Ag–Pb–Te–Se-bearing Co–Ni–Cu sulfides, in prehnite–chlorite gangue. Fluid inclusions indicated Co–Ni arsenide precipitation at 170 C for Usseglio, whereas for the Sardinian system late sulfide deposition occurred within the 52–126 C range. Ore fluids in both systems are NaCl-CaCl2-bearing basinal brines. The chlorite geothermometer at Piazza provides the range of 200–280 C for ore deposition from CO2-poor fluids. Enrichments in Se and negative 13C in carbonates suggest interaction with carbonaceous shales. These deposits involve issues about source rocks, controls on Co/Ni and possible role of arsenic and carbonate components towards economic mineralization

Polymetallic mineralization in Ediacaran sedimentsin the Żarki-Kotowice area, Poland

In one small mineral vein in core from borehole 144-Ż in the Żarki-Kotowice area, almost all of the ore minerals known from related deposits in the vicinity occur. Some of the minerals in the vein described in this paper, namely, nickeline, hessite, native silver and minerals of the cobaltite-gersdorffite group, have not previously been reported from elsewhere in the Kraków-Lubliniec tectonic zone. The identified minerals are chalcopyrite, pyrite, marcasite, sphalerite, Co-rich pyrite, tennantite, tetrahedrite, bornite, galena, magnetite, hematite, cassiterite, pyrrhotite, wolframite (ferberite), scheelite, molybdenite, nickeline, minerals of the cobaltitegersdorffite group, carrollite, hessite and native silver. Moreover, native bismuth, bismuthinite, a Cu- and Ag-rich sulfosalt of Bi (cuprobismutite) and Ni-rich pyrite also occur in the vein. We suggest that, the ore mineralization from the borehole probably reflects post-magmatic hydrothermal activity related to an unseen granitic intrusion located under the Mesozoic sediments in the Żarki-Pilica area

Orthorhombic 11C pyrrhotite from Michałkowa, Góry Sowie Block, The Sudetes, Poland - preliminary report

This study provides the preliminary report about first occurrence of orthorhombic 11C pyrrhotite (Fe (1-x) S) from the Sudetes, Poland. Samples of pyrrhotite-containing two-pyroxene gabbro were found in a classic pegmatite locality in Michałkowa near Walim in the Góry Sowie Block. Based on microscopic methods, pyrrhotite is associated with pentlandite, chalcopyrite, chromite, ilmenite, gersdorffite, magnetite, biotite, magnesio-hornblende, clinochlore, lizardite and talc. X-Ray diffraction (XRD) indicate that pyrrhotite has orthorhombic 11C structure and it is characterized by: a = 3.433(9) Å, b = 5.99(2) Å, c = 5.7432(5) Å, β = 90º and d 102 = 2.06906 Å. Mössbauer studies confirmed the XRD data. Pyrrhotite has three sextets with hyperfine parameter values 30.8 T for sextet A, 27.9 T and 25.8 T for sextets B and C respectively, indicating orthorhombic structure, the composition near Fe 10 S 11 and x = 0.0909

New ore minerals from the Kingash ultramafic massif, Northwestern Eastern Sayan

The paper discusses earlier poorly studied mineralized rocks of the Kingash ultramafic complex in the Kan Block of the Eastern Sayan, including the large Cu–Ni–PGE deposit of the same name. Despite many researchers' increased interest in the Kingash massif, a number of questions related to the petrology, formation mechanism, and localization of Cu–Ni–PGE ore remain controversial. Along with already known ore minerals, we have identified and described a number of new mineral species: argentite, Fe-enriched sperrylite, a bismuth variety of merenskyite, gersdorffite, cobaltite, and thorianite. The ore minerals are distinguished by a higher relative amount of Fe, and this makes the Kingash deposits close to other Paleoproterozoic Cu–Ni deposits, e.g., the Jinchuan in China, Pechenga in Russia, Ungava in Canada, Mt. Scholl in Australia, etc

Mineralogical Characterization of Uranium Ores, Blends and Resulting Leach Residues from Key Lake Pilot Plant, Saskatchewan, Canada

The production and storage of uranium mine mill tailings have the potential to contaminate local groundwater and surface waters with metals and metalloids. As such, an understanding of the solids reservoirs for potential contaminants in uranium ore blends and leach residues (solid wastes generated by the milling of ore) is required to predict long-term controls on these contaminants in tailings porewaters. This study characterized the distribution of the elements of concern (EOCs; As, Mo, Ni, and Se) in uranium ores and waste rock used to blend the mill feeds in the milling process and leach residues from the Key Lake mining operation, Saskatchewan. This study also evaluated the alteration of the clay minerals in these uranium ores, waste rocks and leach residues. X-ray diffraction, electron micro-probe, and mineral liberation analyses showed that the reservoirs for As, Mo, Ni, and Se (in ores and ore blends) were dominated by sulphides including cobaltite, gersdorffite, molybdenite, pyrite, galena and chalcopyrite, secondary Ni-arsenates (annabergite?), Fe-arsenate (scorodite?) and Ni-Co/Ni-sulfates. The secondary arsenates and sulfates present in special waste were identified as major As, Mo, Ni, and Se bearing minerals and most likely the product of oxidation of arsenide-bearing sulphide minerals within the special waste rock. Analyses also showed that sulphides and arsenates occurred in trace amounts in the ores and special waste rock (0.5 to 1.0 wt %). Data showed that 55 to 90% pyrite, 36 to 51% chalcopyrite, 23 to 37% molybdenite, and 52 to 70% galena remained unleached in the leach residues after milling of the ore blends. The percentages of unleached minerals varied between mill feeds and were dependent on the grain-size distribution and the degree of mineral liberation. Cation exchange capacity (CEC) analysis indicated an increase of the CEC values in the leach residues suggesting possible evolution of 2:1 layers into high-charge layers during the milling