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Geology of Ore Deposits - Pyrite ores on the flanks of the Saum copper–zinc massive sulfide deposit are clastic sediments intensely transformed under conditions of acid diagenesis. Colusite...  相似文献   
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The porous fine-grained to microcrystalline copper-zinc ore of the Semenov-2 hydrothermal field, a site in the Semenov hydrothermal cluster discovered in 2007 (13°31′N, MAR), is anomalously enriched in Au (22–188 ppm) and Ag (127–1787 ppm). Chalcopyrite, isocubanite, würtzite, and opal are major minerals; sphalerite, marcasite, pyrite, and covellite are auxiliary; and galena, pyrrhotite, native gold, silver telluride, barite, and aragonite are sporadic. Gold containing 0.31 to 23.07 wt % Ag occurs as up to 9-μm-sized subhedral, dendritelike, and elongated grains mostly hosted in opal and less frequently in sphalerite and in pores within isocubanite-chalcopyrite aggregate. An elongated grain (2 × 4 μm in size) of the Ag-Te phase was found in a pore. So far only basalts have been dredged from the Semenov-2 field, but anomalous gold and silver concentrations suggest the influence of ultramafic rocks; the latter were found 1.5 km westward, in the Semenov-1 hydrothermal field. Mineral assemblage and morphology of gold particles indicate its primary origin in contrast to the hydrothermal fields hosted in basalts, where gold is a product of remobilization. Zonal gold grains, found on oceanic floor for the first time, are characterized by low Ag content in the cores and high Ag content in the outer rims, reflecting variation in formation conditions.  相似文献   
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Geology of Ore Deposits - The article describes magnetite–sulfide assemblages of minerals containing native gold and tellurides in the Pb–Zn–Fe ores of the Aktash skarn deposit in...  相似文献   
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The Slyudyangorsk muscovite deposit in the southern Urals was explored and mined in 1926–1957. By the mid-1950s, 104 veins of quartz–feldspar pegmatites including 21 muscovite-bearing veins have been found. Pegmatites with giant black Y-bearing epidote crystals are crosscut by veins with giant muscovite crystals, which, in turn, are intersected by veins of two-mica–quartz–two-feldspar pegmatites with rare-metal and REE mineralization. Microprobe data on compositions of complex Ti–Ta–Nb oxides [fergusonite-(Y), samarskite-(Y), euxenite-(Y), polycrase-(Y), columbite-(Fe), pyrochlore supergroup] are characterized, as well as of uraninite, ilmenorutile, scheelite, Y-bearing epidote, certain sulfides and rock-forming minerals from the Slyudyanogorsk deposit. The morphology and interrelation of minerals indicate that they are the result of crystal growth in cavities rather than of metasomatic replacement of gneisses, as has been suggested earlier. Thus, it is more promising for rare-metal and REE minerals in the Slyudorudnik area to be found in igneous rocks (granitic muscovite–quartz–feldspar pegmatites with the Nb–Ta–Ti–Y–U–W–Mo mineralization) than in metasomatic rocks.  相似文献   
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Silver sulfoselenide (Ag,Cu)9Se2S4 from ore of the Valunisty Au-Ag deposit on the Chukchi Peninsula is described for the first time. The mineral occurs in mineralized quartz-adularia veins, where it associates with chalcopyrite, sphalerite, galena, and electrum and replaces arsenpolybasite. It forms anhedral grains up to 0.2 mm in size. The reflectivity of sulfoselenide is moderate, no anisotropy is observed, and the microhardness is very low. The chemical composition of the mineral differs from other known members of the Ag-Se-Se-S system: the S/Se ratio of the mineral is 2/1 and the (Ag + Cu)/(Se + S) ratio is about 1.5.  相似文献   
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The paper presents new data on physico-chemical parameters of the Neoproterozoic–Early Cambrian plume magmatism in the Paleo-Asian Ocean. The data on clinopyroxenes show the plume-related plateaubasalt magmatic systems of the Katun’ paleoseamounts, which interacted with mid-ocean ridge (MOR) magmas. The Kurai paleoseamount consists mainly of plateaubasalt systems, and the Agardag ophiolites represent products of OIB–type “hot-spot” within-plate magmatism. Our study of inclusions showed that the melts of the Katun’ and Kurai paleoseamounts crystallized at lower temperatures (1130–1190 °C) compared to the Agardag ophiolites (1210–1255 °C). The petrochemical analysis of the melt inclusions showed that the Katun’ and Kurai magmatic systems are different from the Mg- and Ti-richer melts of the Agardag ophiolites: the former are similar to the magmas of the Nauru Basin and Ontong Java Plateau (western Pacific), whereas the latter possess geochemical affinities to OIB-type magmatism. The rare-element compositions of the melts of the Katun’ and Kurai paleoseamounts correspond to those of the Ontong Java Plateau and Nauru Basin lavas. The numerically simulated parameters of the Katun’ paleoseamount primary magmas agree with the data on the magmatic systems of the Siberian Platform and Ontong Java Plateau. For the Kurai paleoseamount, the simulated results suggest interaction of deep-seated OIB-type magmatic systems with MOR ones. The Agardag ophiolites were formed in relation to mantle plume activity at the initial stages of paleo-oceanic complexes formation.  相似文献   
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The method of singular spectral analysis (SSA) is described and used to analyze the series of Wolf numbers that characterizes solar activity from 1748 until 1996. Since this method is relatively new, we detail its algorithm as applied to the data under study. We examine the advantages and disadvantages of the SSA method and the conditions for its applicability to an analysis of the solar-activity data. Certain regularities have been found in the dynamics of this series. Both short and long (80–100-year) periodicities have been revealed in the sunspot dynamics. We predict the solar activity until 2014.  相似文献   
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Data on melt inclusions in minerals provide direct information on the physicochemical petrogenetic parameters of Late Cenozoic basaltic complexes in the Southern Baikal and Southern Khangai Volcanic Areas (SBVA and SKVA, respectively) in Central Asia. Newly obtained data on inclusions in olivine reveal differences between the temperatures of the magmatic systems that produced basalts in SBVA and SKVA. The comparison of the experimentally determined homogenization temperatures and parameters calculated from data on the composition of glasses in the melt inclusions allowed us to realistically evaluate the temperatures of the petrogenetic processes that generated Late Cenozoic basaltic complexes in SBVA (1130–1160°C and 1175–1250°C) and SKVA (1145–1185°C, 1210–1270, and about 1300–1310°C). The analysis of fluid phases in the inclusions testifies that basaltic melts in SBVA were rich in carbon dioxide, which ensured elevated pressures (up to 5–6.6 kbar) during the crystallization of the minerals. Data on the composition of inclusions in the olivine highlight differences between the chemistries of magmatic systems in the two territories: elevated TiO2, Al2O3, and CaO concentrations at relatively low FeO and MgO contents in the SBVA melts as compared to analogous concentrations in the SKVA basaltic magmas. The petrochemical and geochemical parameters of the primary melt inclusions and the composition of the olivine generally testify that deep plume magmatic processes were actively involved in the generation of basalts in both SBVA and SKVA. Data on melt inclusions in olivine and the composition of the clinopyroxene reveal similarities between the geochemistry, mineralogy, and crystallization parameters of Late Cenozoic basalts in both SBVA and SKVA and Cretaceous-Paleogene basalts in the Tien Shan and their certain differences from the plume-related systems of the OIB type. These data suggest that the geodynamic environment of the Cenozoic and Late Mesozoic intraplate plume magmatism in Central Asia were different from the geodynamic environment of typical long-lived mantle plumes like that at Hawaii.  相似文献   
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