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1.
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
2.
O. Yu. Plotinskaya E. O. Groznova A. I. Grabezhev K. A. Novoselov 《Geology of Ore Deposits》2010,52(5):392-409
The Biksizak silver-base-metal occurrence is situated in the Birgil’da-Tomino ore cluster of the East Ural Zone. The mineralization
is hosted in the Silurian marble (Eastern site) and limestone interbeds in andesitic dacite (Western site). Four mineral assemblages
have been established: the earliest hematite-magnetite, the subsequent pyrite-arsenopyrite and chalcopyrite-sphalerite occurring
only in the Eastern site, and fahlore-chalcopyrite known only from the Western site. The closest positive correlation links
Cu-Zn-Ag, Zn-Pb, Cu-Ag, and Zn-Au. The correlation between chemical elements varies depending on the localization of the ore.
Correlation pairs Au-Ag, Au-Cu, Pb-Ag, and Pb-Cu are characteristic of ore from the Eastern site and are not established in
the Western site. In the Eastern site Cu/(Zn + Pb) in ore is < 1, whereas in the Western site this ratio is markedly higher
than unity. As follows from fluid inclusion study and mineral geothermometry, ore minerals at the Bilsizak occurrence were
formed at a temperature of 300 to 150°C from low- and moderate-saline chloride fluids with 1–9 wt % NaCl equiv. The data obtained
show that the Biksizak occurrence was localized at the margin of a porphyry system characterized by hydrothermal and skarn
processes. 相似文献
3.
Yu. V. Bataleva Yu. N. Palyanov Yu. M. Borzdov I. D. Novoselov O. A. Bayukov N. V. Sobolev 《Petrology》2018,26(6):565-574
Of great importance in the problem of redox evolution of mantle rocks is the reconstruction of scenarios of alteration of Fe0- or Fe3C-bearing rocks by oxidizing mantle metasomatic agents and the evaluation of stability of these phases under the influence of fluids and melts of different compositions. Original results of high-temperature high-pressure experiments (P = 6.3 GPa, T = 1300–1500°С) in the carbide–oxide–carbonate systems (Fe3C–SiO2–(Mg,Ca)CO3 and Fe3C–SiO2–Al2O3–(Mg,Ca)CO3) are reported. Conditions of formation of mantle silicates with metallic or metal–carbon melt inclusions are determined and their stability in the presence of CO2-fluid representing the potential mantle oxidizing metasomatic agent are estimated. It is established that garnet or orthopyroxene and CO2-fluid are formed in the carbide–oxide–carbonate system through decarbonation, with subsequent redox interaction between CO2 and iron carbide. This results in the formation of assemblage of Fe-rich silicates and graphite. Garnet and orthopyroxene contain inclusions of a Fe–C melt, as well as graphite, fayalite, and ferrosilite. It is experimentally demonstrated that the presence of CO2-fluid in interstices does not affect on the preservation of metallic inclusions, as well as graphite inclusions in silicates. Selective capture of Fe–C melt inclusions by mantle silicates is one of the potential scenarios for the conservation of metallic iron in mantle domains altered by mantle oxidizing metasomatic agents. 相似文献
4.
I. L. Gufeld A. V. Korol’kov O. N. Novoselov E. N. Khrulev 《Journal of Volcanology and Seismology》2009,3(6):421-431
This paper is concerned with the correlation of fast local processes that generate geoacoustic emissions and the regional character of excitation in the geologic medium prior to large earthquakes. It is shown that this comparison is possible based on the unifying process of vertical energy transport due to the earth’s degassing. For the first time here, we examine local geoacoustic characteristics by analyzing Poincare diagrams and developing difference equations that describe dynamic changes in the characteristics of acoustic emission sources. Based on this concept, and incorporating the continuity of geoacoustic emissions, we suggest a decompressional model of seismoacoustic noise and geoacoustic emissions as a component of the noise. 相似文献
5.
A model is development for the kinetic and thermodynamic simulation of the interaction of seawater and its metamorphosed derivatives with crustal rocks in slow-spreading ridges. The thermodynamic modulus of the model is based on the GEOCHEQ complex, which makes it possible to simulate equilibria in systems of aqueous solutions-minerals-gases. The calculating code was modified and adjusted for the thermodynamic-kinetic simulation of the passage of irreversible solution-rock reactions with time. The simulations were carried out for a simplified crustal vertical section of slow-spreading (Hess-type) ridges, which consist only of mantle peridotites (spinel harzburgites). The results of our simulations demonstrate that the degree of peridotite serpentinization under the effect of low-temperature seawater when the rocks are exposed at the seafloor surface remains very low even after 10000 years of interaction. Serpentinization becomes efficient only at temperatures of 130–150°C at crustal depths of 3.5–4.5 km. The results of our simulations allowed us to develop a thermodynamic model for the origin of hydrothermal systems in peridotites in slow-spreading ridges, with regard for the major stages in the material and tectonic evolution of the Hess crust. 相似文献
6.
7.
This paper reports the first results of kinetic and thermodynamic modeling of interaction between the komatiitic material
of the earliest terrestrial ocean and seawater. The modeling was aimed at reconstructing geochemical effects accompanying
the early evolution of the earth’s outer shells, atmosphere, and hydro-sphere. We also explored the character of mineral transformations
in the protooceanic crust during its hydro-thermal alteration. Kinetic and thermodynamic simulation by means of the GEOCHEQ
program complex was the main tool of our study. The results of modeling allowed us to estimate the character of the environment
and the duration of the formation of the oldest banded iron formation (BIF) and volcanogenic massive sulfide (VMS) deposits
and reconstruct main trends in the compositional variations in the hydrosphere and atmosphere that coexisted with them. 相似文献
8.
9.
O. Yu. Plotinskaya E. O. Groznova V. A. Kovalenker K. A. Novoselov R. Seltmann 《Geology of Ore Deposits》2009,51(5):371-397
The Bereznyakovskoe ore field is situated in the Birgil’da-Tomino ore district of the East Ural volcanic zone. The ore field
comprises several centers of hydrothermal mineralization, including the Central Bereznyakovskoe and Southeastern Bereznyakovskoe
deposits, which are characterized in this paper. The disseminated and stringer-disseminated orebodies at these deposits are
hosted in Upper Devonian-Lower Carboniferous dacitic-andesitic tuff and are accompanied by quartz-sericite hydrothermal alteration.
Three ore stages are recognized: early ore (pyrite); main ore (telluride-base-metal, with enargite, fahlore-telluride, and
gold telluride substages); and late ore (galena-sphalerite). The early and the main ore stages covered temperature intervals
of 320–380 to 180°C and 280–300 to 170°C, respectively; the ore precipitated from fluids with a predominance of NaCl. The
mineral zoning of the ore field is expressed in the following change of prevalent mineral assemblages from the Central Bereznyakovskoe
deposit toward the Southeastern Bereznyakovskoe deposit: enargite, tennantite, native tellurium, tellurides, and selenides
→ tennantite-tetrahedrite, tellurides, and sulfoselenides (galenoclausthalite) → tetrahedrite, tellurides, native gold, galena,
and sphalerite. The established trend of mineral assemblages was controlled by a decrease in $
f_{S_2 }
$
f_{S_2 }
, $
f_{Te_2 }
$
f_{Te_2 }
and $
f_{O_2 }
$
f_{O_2 }
and an increase in pH of mineral-forming fluids from early to late assemblages and from the Central Bereznyakovskoe deposit
toward the Southeastern Bereznyakovskoe deposit. Thus, the Central Bereznyakovskoe deposit was located in the center of an
epithermal high-sulfidation ore-forming system. As follows from widespread enargite and digenite, a high Au/Ag ratio, and
Au-Cu specialization of this deposit, it is rather deeply eroded. The ore mineralization at the Southeastern Bereznyakovskoe
deposit fits the intermediate- or low-sulfidation type and is distinguished by development of tennantite, a low Au/Ag ratio,
and enrichment in base metals against a lowered copper content. In general, the Bereznyakovskoe ore field is a hydrothermal
system with a wide spectrum of epithermal mineralization styles. 相似文献
10.
E. V. Belogub K. A. Novoselov V. A. Kotlyarov I. B. Fadina 《Geology of Ore Deposits》2007,49(7):583-589
Three types of oxidized ores are identified in the Ik-Davlyat gold-base-metal deposit in the southern Urals: (1) carbonate-sericite-chlorite mineralized rock, (2) vein-shaped quartz-goethite-illite clay, and (3) limonitized rock related to veins. Heavy concentrate of the first type of ore is composed of goethite, rutile, native gold Au0.91Ag0.08Cu0.01, and chalcophanite Zn1.02Mn2.98O4 · 3H2O. The second type of ore contains goethite, rutile, Pb-bearing jarosite, native gold Au0.90?0.93Ag0.06?0.08Cu0?0.01Fe0?0.01, silver amalgamide (schachnerite) Ag0.75Hg0.97Au0.98-Ag0.75Hg0.97Au0.28, coronadite (Pb1.72Mn7.51Fe0.41Cu0.36)8O16, a chalcophanite-hydrohetaerolite mixture, and cerussite. Gold of the highest fineness (Au0.98Ag0.01Cu0.01) is associated with silver amalgamide. The third type of ore is quite similar to the first variety but contains a jarosite impurity. The composition of oxidized ores indicates a difference in composition of primary ores, in particular, the presence of lead minerals in primary veins. The first finding of chalcophanite in Russia is confirmed by chemical, optical, and X-ray data. 相似文献