Добірка наукової літератури з теми "Sulphide-bearing Aggregate"

Abstract Bakyrchik and Bolshevik both are sediment-hosted disseminated gold deposits. They are located in Eastern Kazakhstan (4 km in distance between deposits) and include in the Western Qalba metallogenic zone. They originated in late Paleozoic age along structured line between palaeocontinents of Kazakhstan and Altai-Mongol. The purpose of this paper is designation of typomorphic features of gold-bearing arsenopyrite and pyrite minerals, determination of chemical composition of these two sulfides minerals. The arsenopyrite and pyrite are the main objects for analytical study of gold-bearing sulfide minerals, their different textures, morphology of the crystals and aggregates. The studies of ore samples and minerals were carried out by methods of optical microscope, X-ray diffraction, X-ray fluorescence and electron microprobe analyses. The analytical study of sulphide minerals has shown that the arsenopyrite is acicular and tabular, pyrite has three varieties - globular, hexahedral and pentahedral forms in three rock samples of the carbonaceous-terrigenous formation in the deposits.

A mesophilic, slightly halophilic, obligately methylotrophic, methanogenic archaeon, designated strain GTA13T, was isolated from natural gas-bearing confined aquifers in the Minami-Kanto gas field, Japan. The cells were non-motile, slightly irregular cocci, 0.7–1.0 µm in diameter and occurred singly, in pairs or as small aggregates. The cells grew with tri- or dimethylamine but not with H2/CO2, formate, acetate, methanol or dimethyl sulphide. Vitamins, sodium and magnesium were required for growth. Optimal growth occurred at pH 7.0–7.5, 35 °C, 0.35–0.40 M NaCl and 15–50 mM MgCl2. The NaCl range for growth was 0.2–1.3 M. The DNA G+C content was 43.7 mol%. Strain GTA13T showed highest levels of 16S rRNA gene sequence similarity with Methanohalophilus portucalensis FDF-1T (96.4 % sequence similarity) and Methanohalophilus halophilus DSM 3094T (96.0 %). On the basis of physiological and phylogenetic features, strain GTA13T is considered to represent a novel species of the genus Methanohalophilus , for which the name Methanohalophilus levihalophilus sp. nov. is proposed. The type strain is GTA13T ( = NBRC 110099T = DSM 28452T). An emended description of the genus Methanohalophilus is also proposed.

AbstractMoolooite, a naturally occurring hydrated copper oxalate has been identified in a sulphide-bearing quartz outcrop 12 km east of Mooloo Downs station homestead (25° 01′ 30″ S., 116° 06′ 30″ E.), Western Australia. It has apparently formed by the interaction of solutions derived from bird guano and weathering copper sulphides. Partial microchemical analysis indicates a composition corresponding to CuC2O4 · 0.44H2O. The infra-red spectrum is similar to that of the artificial compound with diagnostic absorption bands at 3490, 2975, 2935, 1980, 1940, 1660, 1365,1320, 830, 510, 390, and 315 cm−1. Powder X-ray diffraction patterns indicate a disordered structure with orthorhombic symmetry; a 5.35, b 5.63, c 2.56 Å, Z = 1. The strongest lines of the powder pattern are [d Å, I, hkl]: 3.88, 100, (110); 2.50, 30, (120); 2.33, 18, (011); 2.31, 25,(101); 2.14, 20, (111); 1.938, 18, (220); 1.787, 25, (121); 1.753, 30, (211); 1.216, 15, (112). Unindexed very weak diffuse lines on some patterns can be indexed assuming a supercell with a′ = a, b′ = 2b, c′ = 2c indicating the presence of ordered crystallites.Moolooite occurs as micro-concretionary crusts and powder in cracks and solution cavities resulting from sulphide oxidation. It is found associated with opaline silica, gypsum, broehantite, antlerite, atacamite, whewellite, sampleite, and libethenite. It is turquoise-green in colour with similar streak, lustre dull to waxy, calculated density 3.43 g/cm3. Moolooite is composed of aggregates of generally sub-micrometre sized equidimensional crystallites with α ∼ 1.57 and γ ∼ 1.95.By analogy with artificial copper oxalate, moolooite is constructed from infinite ribbon-like elementary structural units consisting of alternating Cu2+ and (C2O4)2− ions. These units are arranged en echelon in layers which are stacked with displacements so that octahedral coordination of copper ions is completed by oxygen atoms in adjacent layers. The minimal role played by water in the structure and composition of moolooite distinguish it from other oxalate minerals. Because of the zeolitic character of the water a general formula CuC2O4 · nH2O (0 ⩽ n ⩽ 1) appears to be appropriate.

Abstract The Cheoeum vent field (CVF) is the first example of an inactive ultramafic-hosted seafloor massive sulphide (SMS) deposit identified in the middle part of the Central Indian Ridge. Here, we report on the detailed mineralogy and geochemistry of ultramafic-hosted sulphide sample atop a chimney, together with a few small fragments. Hydrothermal chimneys are characterised by high concentrations of Au (up to 17.8 ppm) and Sn (up to 1720 ppm). The sulphide mineralisation in the CVF shows (1) early precipitation of anhedral sphalerite and pyrite–marcasite aggregates under relatively low-temperature (< 250 °C) fluid conditions; (2) intensive deposition of subhedral pyrrhotite, isocubanite, chalcopyrite, Fe-rich sphalerite (Sp-III), and electrum from high-temperature (250–365 °C) and reduced fluids in the main mineralisation stage; and (3) a seawater alteration stage distinguished by the mineral assemblage of marcasite pseudomorphs, altered isocubanite phase, covellite, amorphous silica, and Fe-oxyhydroxides. Electrum (< 2 μm in size) is the principal form of Au mineralisation and is mainly associated with the main mineralisation stage. The consistently high fineness of electrum (801 to 909‰) is indicative of the selective saturation of Au over Ag in the fluid during high-temperature mineralisation, which differs from the Au mineralisation associated with typical basaltic-hosted hydrothermal systems on mid-ocean ridges. Tin is mainly substituted in structures of sphalerite, isocubanite, and chalcopyrite as a solid solution, and not as mineral inclusions. The continuously ascending hydrothermal fluids enable the early formed Sn-bearing sulphide to be dissolved and reprecipitated, producing significantly Sn-enriched replacement boundaries between isocubanite and Sp-III. This study suggests that Au–Sn mineralisation could be facilitated by the low redox potential of ultramafic-hosted hydrothermal systems such as in the CVF, which may be a common occurrence along slow-spreading mid-ocean ridges.