Добірка наукової літератури з теми "Clausthalite"

New Occurrence of Clausthalite (PbSe) in the Sudetes (SW Poland)The presence of clausthalite in the area of old mining works near Dziećmorowice in the Sowie Mts (SW Poland) is reported here for the first time. The identification of the clausthalite is based on macro- and microscopic observations, reflectance measurements, chemical analyses and X-ray diffraction data. The clausthalite, together with uraninite, forms veinlets in a breccia comprising <50% calc-silicate rock fragments. Different polishing hardnesses suggest some variation in the mineral structure of individual clausthalite grains. Chemical spot analyses do not reveal elements other than Pb and Se though calculated unit-cell parameters may suggest minor substitution of S for Se.

Own Se minerals, first established in primary ores of VMS deposits of the Urals, are described. Instrumental neutron activation analysis of bulk ore samples, mineral monofractions and local methods of analysis: LA-ICP- MS, electron probe microanalysis and analytical electron microscopy were used. CSe in ores of the Urals to 977 g/t. Significant positive correlation of Se with Te, S, Fe, Co, Mo, Hg, Bi is characteristic. Selenium is con- centrated in the main sulfides, mainly in pyrite (73 g/t), chalcopyrite 49 g/t, pyrrhotite 48 g/t; in sphalerite usually <10 g/t. High Se content (up to 1–3 wt.%) occurs in the minor and rare minerals from massive sulfide ores (mainly compounds of Pb, Te, Bi): tetradymite, galena, tellurobismuthite, altaite, wittichenite. Own Se minerals in ores are represented by kawazulite, clausthalite, galena-clausthalite Pb(Se,S), micron inclusions composition (Ag, Cu)2(Se, S), (Ag, Pb)3(Te, Se)S, (Ag, Pb)2(S, Se).

AbstractPrecious and base metal selenide minerals have been identified in gold-bearing carbonate veins cutting Middle Devonian limestones of the Torquay Limestone Group at Hope's Nose, Torquay. The selenide assemblage consists of clausthalite (PbSe), tiemannite (HgSe), klockmannite (CuSe), umangite (Cu3Se2), tyrrellite (Cu,Co,Ni)3Se4, trustedtite (Ni3Se4), penroseite (NiSe2), naumannite (Ag2Se), eucairite (AgCuSe) and fischesserite (Ag3AuSe2), only clausthalite having previously been reported from Britain. They are associated with palladian gold, gold, hematite, and accessory pyrite and chalcopyrite in a gangue consisting predominantly of calcite; alteration products include cerussite, malachite, aragonite and goethite.The relative abundance of Au, Ag, Hg and Se is a characteristic feature in the uppermost parts of some precious metal ‘epithermal’ systems. The occurrence at Hope's Nose is related to both structural and lithological factors: a deep-seated NW-SE structural lineament, the Lundy-Sticklepath-Lustleigh-Torquay fault; local thrusting, and to an association of basic-intermediate igneous rocks with a sedimentary sequence including carbonaceous shales and limestones. The mineralization is considered to be post-Variscan, probably Permo-Triassic in age.

Significant selenium enrichment associated with selenides and previously unknown Ag-Pb-Sb, Ag-Sb and Pb-Sb sulfosalts has been discovered in hydrothermal ore veins in the Anthony of Padua mine near Poličany, Kutná Hora ore district, central Bohemia, Czech Republic. The ore mineralogy and crystal chemistry of more than twenty silver minerals are studied here. Selenium mineralization is evidenced by a) the occurrence of selenium minerals, and b) significantly increased selenium contents in sulfosalts. Identified selenium minerals include aguilarite and selenides naumannite and clausthalite. The previously unknown sulfosalts from Kutná Hora are identified: Ag-excess fizélyite, fizélyite, andorite IV, andorite VI, unnamed Ag-poor Ag-Pb-Sb sulfosalts, semseyite, stephanite, polybasite, unnamed Ag-Cu-S mineral phases and uytenbogaardtite. Among the newly identified sulfides is argyrodite; germanium is a new chemical element in geochemistry of Kutná Hora. Three types of ore were recognized in the vein assemblage: the Pb-rich black ore (i) in quartz; the Ag-rich red ore (ii) in kutnohorite-quartz gangue; and the Ag-rich ore (iii) in milky quartz without sulfides. The general succession scheme runs for the Pb-rich black ore (i) as follows: galena – boulangerite (– jamesonite) – owyheeite – fizélyite – Ag-exces fizélyite – andorite IV – andorite VI – freieslebenite – diaphorite – miargyrite – freibergite. For the Ag-rich red ore (ii) and ore (iii) the most prominent pattern is: galena – diaphorite – freibergite – miargyrite – pyragyrite – stephanite – polybasite – acanthite. The parallel succession scheme progresses from Se-poor to Se-rich phases, i.e., galena – members of galena – clausthalite solid solution – clausthalite; miargyrite – Se-rich miargyrite; acanthite – aguilarite – naumannite. A likely source of selenium is in the serpentinized ultrabasic bodies, known in the area of “silver” lodes in the South of the ore district, which may enable to pre-concentrate selenium, released into hydrothermal fluids during tectonic events. The origin of the studied ore mineralization is primarily bound to the youngest stage of mineralization of the whole ore district, corresponding to the Ag-Sb sequence of the ´eb´ ore type of the Freiberg ore district in Saxony (Germany) and shows mineralogical and geochemical similarities to low-sulfidation epithermal-style Ag-Au mineralization.

Tilkerodeite, ideally Pd2HgSe3, is a new platinum-group selenide from the Eskaborner Stollen (Adit Eskaborn) at Tilkerode, Harz Mountains, Germany. Tilkerodeite crystals occur as euhedral inclusions in tiemannite or as extremely fine-grained lamellar aggregates (grain-size up to 3 μm) in a dolomite–ankerite matrix, together with clausthalite, tiemannite, jacutingaite, stibiopalladinite, and native gold. Neighbouring Se-bearing minerals include tischendorfite and chrisstanleyite. Tilkerodeite is opaque with a metallic luster, and is flexible in blade-like crystals, with perfect basal cleavage {001}. In plane-polarized light, tilkerodeite is brownish-grey. It is weakly bireflectant, and weakly pleochroic in shades of light-brown and grey. The anisotropy is weak, with rotation tints in weak shades of greenish-brown and grey-brown. The range of reflectance is estimated in comparison to clausthalite with 45–50%. Electron-microprobe analyses yield the mean composition (wt. %) Se 32.68, Hg 26.33, Pt 20.62, Pd 15.89, Pb 2.72, Cu 0.66, S 0.27, total 99.17 wt. %. The empirical formula (based on six atoms pfu) is (Pd1.08Pt0.76Pb0.09Cu0.07)Σ2.00Hg0.95(Se2.98S0.07)Σ3.05. The ideal formula is Pd2HgSe3. Tilkerodeite is trigonal, with Pt4Tl2Te6-type structure, space group P3–m1, a = 7.325(9) Å, c = 5.288(6) Å, V = 245.7(9) Å3, and Z = 2. It is the Pd-analogue of jacutingaite. Tilkerodeite formed hydrothermally, possibly involving the alteration of tiemannite by low-temperature oxidizing fluids. The new species has been approved by the IMA-CNMNC (2019-111) and is named after the locality. Tilkerode is the most important selenide-bearing occurrence in Germany and type locality of naumannite, eskebornite, and tischendorfite.

Abstract Nickeltyrrellite, ideally CuNi2Se4, is a new selenide species from the El Dragón mine, Department of Potosí, Bolivia. It most frequently occurs as anhedral to subhedral grains (up to 20 μm in size) in association with cerromojonite, klockmannite, clausthalite, and penroseite, forming fracture fillings in pre-existing krut'aite−penroseite solid solutions. Nickeltyrrellite is non-fluorescent, black, and opaque with a metallic luster and black streak. It is brittle, with an irregular fracture and no obvious cleavage and parting. In plane-polarized incident light, nickeltyrrellite is cream to pale pinkish, displaying no internal reflections. Between crossed polarizers, it is isotropic. The reflectance values in air for the COM standard wavelengths are 45.9 (470 nm), 47.6 (546 nm), 48.1 (589 nm), and 49.8 (650 nm). Electron-microprobe spot analyses (n = 28) of the grain populations used for the EBSD study yielded a mean composition of Cu 13.01, Fe 0.27, Co 6.66, Ni 16.98, S 1.04, Se 61.91, total 99.87 wt.%. The empirical formula, normalized to 7 apfu, is Cu1.00(Ni1.42Co0.56Fe0.02)Σ2.00(Se3.84S0.16)Σ4.00. The ideal formula is CuNi2Se4, which requires (in wt.%) Cu 12.79, Ni 23.63, Se 63.58, total 100. EBSD patterns reveal nickeltyrrellite as cubic, space group , with a = 9.99 Å, V = 997.0 Å3, Z = 8. The calculated density is 7.36 g cm−3. It formed in response to alteration of quijarroite + hansblockite + watkinsonite + clausthalite + penroseite aggregates by oxidizing, low-T, Cu-Ni-Co-Pb-bearing fluids at a fSe2/fS2 ratio greater than unity. Nickeltyrrellite is a new selenide belonging to the tyrrellite subgroup of the spinel supergroup. The new species has been approved by the IMA-CNMNC (2018-110) and is named for constituting the Ni-analogue of tyrrellite.

Mineralization of Te and Se was found in gold deposits and uranium occurrences, located in the Paleoproterozoic greenstone belts in Northern Fennoscandia. These deposits are of different genesis, but all of them formed at the late stages of the Svecofennian orogeny, and they have common geochemical association of metals Au, Cu, Co, U, Bi, Te, and Se. The prevalent Te minerals are Ni and Fe tellurides melonite and frohbergite, and Pb telluride altaite. Bismuth tellurides were detected in many deposits in the region, but usually not more than in two–three grains. The main selenide in the studied deposits is clausthalite. The most diversified selenium mineralization (clausthalite, klockmannite, kawazulite, skippenite, poubaite) was discovered in the deposits, located in the Russian part of the Salla-Kuolajarvi belt. Consecutive change of sulfides by tellurides, then by selenotellurides and later by selenides, indicates increase of selenium fugacity, fSe2, in relation to fTe2 and to fS2in the mineralizing fluids. Gold-, selenium-, and tellutium-rich fluids are potentially linked with the post-Svecofennian thermal event and intrusion of post-orogenic granites (1.79–1.75 Ga) in the Salla-Kuolajarvi and Perapohja belts. Study of fluid inclusions in quartz from the deposits in the Salla-Kuolajarvi belt showed that the fluids were high-temperature (240–300 °C) with high salinity (up to 26% NaCl-eq.). Composition of all studied selenotellurides, kawazulite-skippenite, and poubaite varies significantly in Se/Te ratio and in Pb content. Skippenite and kawazulite show the full range of Se-Te isomorphism. Ni-Co and Co-Fe substitution plays an important role in melonite and mattagamite: high cobalt was detected in nickel telluride in the Juomasuo and Konttiaho, and mattagamites from Ozernoe and Juomasuo contain significant Fe. In the Ozernoe uranium occurrence, the main mineral-concentrator of selenium is molybdenite, which contains up to 16 wt.% of Se in the marginal parts of the grains. The molybdenite is rich in Re (up to 1.2 wt.%), and the impurity of Re is irregularly distributed in molybdenite flakes and spherulites.

Iron-oxide copper gold (IOCG)-uranium deposits represent South Australia’s primary resource base for copper production. The presence of daughter radionuclides (RN) from the 238U decay series within the ores necessitates a detailed understanding of their mineralogical deportment as a pre-requisite for attempts to remove or reduce RN concentrations. Research presented in this thesis contributes towards this knowledge by identifying and characterising potential RN-carriers, migration of radiogenic lead via geological processes, and provides evidence for RN sorption during processing. Novel approaches to RN reduction are proposed based on mineralogical-geochemical results. Evidence for migration of Pb within the deposit and during processing is relevant for any assessment of RN deportment, especially since the Pb-chalcogenides galena, clausthalite (PbSe) and altaite (PbTe) are often hosted within Cu-(Fe)-sulphides. Lead isotope values measured in-situ by laser ablation inductively coupled plasma mass spectrometry suggest an overwhelmingly radiogenic origin for Pb and thus extensive decoupling of radiogenic Pb from parent U- and Th-minerals. Calculated 207Pb/206Pb ratios suggest Pb mobilisation during an event that postdates the initial Mesoproterozoic Fe-Cu-Au-U mineralisation event, an interpretation consistent with other studies in the Olympic Cu-Au province which indicate cycles of replacement-remobilization-recrystallization. A nanoscale study of the most common of the three Pb-chalcogenide minerals, clausthalite, by high-angle annular dark field scanning transmission electron microscopy, proved highly instructive for identifying mechanisms of remobilization and overprinting. Characteristic symplectite textures involving clausthalite and host Cu-(Fe)-sulphides are indicative of formation via reaction between Se that pre-existed in solid solution within Cu-(Fe)-sulphides and migrating Pb. Observed superstructuring of clausthalite nanoparticles within chalcopyrite provides a direct link between solid solution and symplectite formation. Sr-Ca-REE-bearing aluminium-phosphate-sulphates (APS) of the alunite supergroup are a minor component of the Olympic Dam orebody. They appear paragenetically late, often replacing earlier REE-minerals. Characterisation of these compositionally zoned phases allowed them to be defined as minerals that span the compositional fields of woodhouseite and svanbergite, and also a REE- and phosphate-dominant group displaying solid solution towards florencite. A nanoscale secondary ion mass spectrometry study of RN distributions in APS minerals in acid-leached copper concentrate revealed that APS minerals readily sorb products of 238U decay, notably 226Ra and 210Pb, whereas U remains in solution. Many APS phases, particularly those that are Pb-bearing, are stable over a wide range of pH and Eh conditions and at temperatures up to 450 °C. As such, synthetic APS phases represent viable candidates not only for the removal of radionuclides from metallurgical streams, but also for their safe storage and isolation from surrounding environments. Ca-Sr-dominant phases display preferential enrichment by Pb (notably 210Pb) during flotation. 210Pb uptake then increases during subsequent acid leaching. Mixed Ca- and Sr-bearing APS phases were synthesised by modifying existing recipes to test the role of compositional variability of APS phases on the sorption rate of Pb from dilute Pb(NO3)2 solution. Lead incorporation by the synthetic APS phases was confirmed, whereby Pb replaces Ca, but not Sr, within the APS crystal structure. Extended X-ray absorption fine structure analysis of the resulting solids reveals the nature of Pb sorption by the synthesized material. The data showed that the dynamic incorporation of Pb by APS phases occurred overwhelmingly at pH 3.5, thus verifying that uptake of Pb by synthetic APS phases may represent a robust mechanism to achieve both reduction and immobilisation of 210Pb within metallurgical processing streams.
Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering & Advanced Materials, 2020