Occurrence Forms of Carbon,Sulfur, and Noble Metals in Deposits of the Black-Shale Formation by the Example of the Degdekan Gold-Ore Deposit (Northeastern Russia)     

V. L. Tauson  R. G. Kravtsova  V. V. Akimov  S. V. Lipko  A. M. Spiridonov  A. E. Budyak  I. Yu. Voronova  O. Yu. Belozerova  K. Yu. Arsentev 《Doklady Earth Sciences》2018,478(1):92-99

Pyrite crystals and ore-bearing shales of the Degdekan deposit were studied by means of XPS, SEM–EDX, EPMA, and AAS. Five peaks of carbon organic forms were identified, conforming to polymer compounds containing either double bonds of carbon or alkyne groups and compounds containing C–OH and C=O bonds, as well as, probably, small amounts of S-containing compounds and those with functional groups of carboxylic acids. Sulfate prevails over sulfite in pyrites; among the surface sulfide forms, disulfide prevails over monosulfide; the presence of polysulfide is registered. The occurrence of various chemical forms of sulfur on the surface might provide for concentrating of microelements including the noble metals (NMs) in their surface-bound forms. The regular behavior of NMs (Au, Pt, Pd, and Ru) depending on the grain sizes (specific surfaces) of pyrite crystals along with the narrow range of the ratios of structural and surface components of the concentrations of different NMs points to NM coprecipitation with pyrite during the same productive stage. No capture of NM-containing carbonaceous phases took place, which should violate the regularity of Au distribution in pyrites of the Sukhoi Log deposit.  相似文献   

The First Results of Tephrochronological Study of Late Pleistocene–Holocene Volcanic Eruptions in the Zhom–Bolok River Valley (Eastern Sayan)     

Shchetnikov  A. A.  Bezrukova  E. V.  Kerber  E. V.  Belozerova  O. Yu.  Kuzmin  M. I.  Ivanov  E. V.  Krainov  M. A.  Filinov  I. A.  Nechaev  I. O. 《Doklady Earth Sciences》2019,486(1):503-506

Doklady Earth Sciences - The first results of tephrochronological studies of Late Pleistocene–Holocene volcanic eruptions in the Zhom-Bolok River valley (Eastern Sayan) are reported. Based on...  相似文献   

Electron Probe Microanalysis of Environmental Samples: Preparation of Reference Materials, Correction for Particle Size Effects and Representative Results on Sediments Recovered from Snow, Power Station Fly Ash and Bone Samples     

Ludmila A. Pavlova  Ludmila Ph. Paradina  Olga Yu. Belozerova 《Geostandards and Geoanalytical Research》2001,25(2-3):333-344

In this paper we report the results of electron probe X-ray microanalysis (EPMA) that was used to study environmental materials. The mode of preparation and certification of reference samples based on a basaltic glass matrix for environmental applications of EPMA is described. These samples were prepared containing scandium, strontium and barium (from 0.03 up to 7% m/m) and an evaluation was made of homogeneity, their stability to local heating, followed by analysis by independent methods for certification of composition. Matrix correction procedures for the EPMA technique have been developed for particles having a size commensurable with the volume of X-ray generation. An analytical equation for the size factor is proposed and two techniques for selecting optimum conditions for the analysis of environmental samples by EPMA are reported. These procedures provided satisfactory results when utilized in analysing sediments recovered from snow, coal fly ash and the bones of animals and fish, results from which can be used as indicators for evaluating the pollution level of the lower atmosphere, surface and ground water, as well as revealing pollution mechanisms.  相似文献   

Biogeochemistry of encrusting sponges of the family Lubomirskiidae in Southern Lake Baikal     

N. N. Kulikova  E. V. Saibatalova  S. M. Boiko  N. A. Semiturkina  O. Yu. Belozerova  A. S. Mekhonoshin  O. A. Timoshkin  A. N. Suturin 《Geochemistry International》2013,51(4):326-337

ICP-MS analyses of encrusting sponges indicate that their predominant chemical elements are, along with Si, by P, Al, Fe, Ca, S, Mg, K, Na, Cu, Mn, Zn, Ti, Ba, and Br. The sponges are most significantly enriched in Al > Cu > Ti > REE > Mn > P relative to their aqueous habitat and in Cu > I > Cd > P > Br > As ≥ S relative to the relatively rudaceous bottom sediments. One of the sources of elements occurring the aqueous habitat and being of vital importance for the activity of the sponges was proved to be the rock substrates.  相似文献   

Dualistic distribution coefficients of elements in the system mineral-hydrothermal solution. I. Gold accumulation in pyrite     

V. L. Tauson  D. N. Babkin  T. M. Pastushkova  T. S. Krasnoshchekova  E. E. Lustenberg  O. Yu. Belozerova 《Geochemistry International》2011,49(6):568-577

The use of trace elements (TE) as geochemical indicators is complicated by the dualism of their distribution coefficients D due to the additional (i.e., above the concentrations of an isomorphic component) incorporation of elements at structural defects of various nature (including the surface of the crystal). A pressing problem in this situation is to determine the true D values that pertain to the structural component of an admixture D ^str and evaluate effects of other modes of TE occurrence. Only upon distinguishing D ^str in the bulk coefficient D ^bulk it is possible to evaluate the ore potential of fluid in terms of certain TE from the composition of a mineral containing the TE. Pyrite synthesized in solutions of variable pH at 450°C and 1 kbar (100 MPa) at fluid portions sampled in a trap is utilized to demonstrate the role of a surface nonautonomous phase (NP) in the incorporation of gold in this mineral. The distribution coefficient of gold between pyrite and hydrothermal solution is 0.14 for “pure” pyrite and 0.05 for As-bearing pyrite (containing 0.02–0.05 wt % As), and these coefficients for NP are 310 and 170, respectively. This increases the D ^bulk for evenly distributed (“invisible”) gold by factors of four and nine. In contrast to the results of earlier studies conducted at room temperature and pressure or parameters close to them, our data demonstrate that the accumulation of “invisible” Au in pyrite is controlled not only by reducing adsorption with the development of Au(0) particles and films but also by Au incorporation in NP developing in the surface layer of the crystal approximately 500 nm thick as chemically bound Au [most likely as Au(I)]. The possible reason for the high absorption capacity of NP is the defect (pyrrhotite-like) structure, which is not saturated with bonds of excess S and sulfoxi onions.  相似文献   

Dualistic distribution coefficients of elements in the system mineral-hydrothermal solution. II. Gold in magnetite     

V. L. Tauson  D. N. Babkin  T. M. Pastushkova  V. V. Akimov  T. S. Krasnoshchekova  S. V. Lipko  O. Yu. Belozerova 《Geochemistry International》2012,50(3):227-245

The system magnetite-Au-hydrothermal solution was employed to continue studying the distribution coefficients of trace elements in system with real crystals. The role of surface nonautonomous phase (NP) is elucidated. The distribution coefficient of an Au structural admixture between magnetite and hydrothermal solution at the experimental conditions [450°C, 1 kbar (100 MPa), and fluid sampling by a trap] is, according to the most representative data, 1.0 ± 0.3, and Au is thus not an incompatible element in magnetite, in contrast to pyrite and arsenopyrite [1], minerals for which this coefficient is much lower than one. The NP is enriched in Au with respect to the rest of the crystal by a factor of more than 4000, and this results in an one order of magnitude increase in the bulk distribution coefficient. Similar to pyrite, the reason for the dualistic nature of the distribution coefficient is the presence of an NP, which contains ∼2000 ± 500 ppm Au. The NP occupies the approximately 330-nm surface layer of the crystal, and the chemically bound Au [Au(III), according to XPS data] admixture is evenly distributed with depth within the layer, which is the reason for the strongly determinate dependences of the concentrations of the evenly distributed Au admixture on the size and specific surface area of the crystal. The occurrence of an NP is controlled by the chemistry of the system. The partial substitution of Fe for Mn and the synthesis of a phase close to jacobsite MnFe₂O₄ results in the disappearance of both the NP itself and the size dependence of the Au concentration. The XPS spectra of O 1s and Fe 2p are used to analyze two models: (i) a single goethite-like (O²⁻/OH⁻∼ 1) phase of variable composition and Fe in more than one valence state and (ii) a heterogeneous structure of alternating domains of wuestite- and goethite-like NP. The reason for the “excess” admixture in the former instance can be vacancies at Fe sites, whereas that in the latter one is the interaction of the admixture with nanometer-in-size nanometer in-size strained domains on the surface of the crystal.  相似文献   

Dualistic distribution coefficients of trace elements in the system mineral–hydrothermal solution. IV. Platinum and silver in pyrite     

V. L. Tauson  S. V. Lipko  K. Yu. Arsent’ev  Yu. L. Mikhlin  D. N. Babkin  N. V. Smagunov  T. M. Pastushkova  I. Yu. Voronova  O. Yu. Belozerova 《Geochemistry International》2017,55(9):753-774

The FeS₂–Ag–Pt–As system was studied using hydrothermal thermogradient synthesis (with internal sampling) of pyrite crystals at a temperature of 500°C and pressure of 1 kbar in ammonium chloridebased solutions. The modes of occurrence of precious metals (PM) were determined using atomic absorption spectrometry (AAS) in its version of statistical selections of analytical data on single crystals (SSADSC), electron microprobe analysis (EMPA), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The concentration of Pt in its structural mode in pyrite is as high as 10–11 ppm and is practically not correlated with the As concentration. The dualistic distribution coefficient of Pt between pyrite and hydrothermal solution is 21 ± 7 for the structural mode and 210 ± 80 for the surface-related mode of this element. No inclusions of either any Pt-bearing minerals or Pt itself was detected. Platinum is an element highly compatible with hydrothermal pyrite and is different in this sense from gold, and pyrite is underestimated as a potential concentrator of platinumgroup elements (PGE). The distribution of Ag in pyrite is highly heterogeneous. The likely reason for this is that the Ag solid solution cannot be quenched, and hence, the Ag concentrations broadly vary and are very unsystematically distributed in natural pyrite crystals. Assuming this hypothesis, the limit for Ag accommodation in FeS₂ can be estimated using SSADSC at 0.09 ± 0.06 wt % under the experimental parameters, and the distribution coefficient of the structural Ag mode is thereby evaluated at 1400 ± 700. When crystallizing together with FeS₂ proustite (Ag₃AsS₃) near its melting point, forms mixtures with dervillite (Ag₂AsS₂), in which Ag deficit is counterbalanced by excess divalent As. The limit of As incorporation into pyrite under these conditions is ≤0.1 wt %. SEM-EDS and XPS data indicate that the surface phases are of three types. In the course of crystal growth, practically two-dimensional nonautonomous phases (NP) are aggregated into submicroscopic and micrometer-sized crystalline bodies (mesocrystals) that largely inherit their unusual minor-element composition from NP and are enriched in Ag, Pt, As, and other minor elements. NP and mesocrystals are enriched in Al, which was transferred into them from the Al-bearing Ti alloy of the reaction containers. Silver occur in the volume of the crystals and on their surface as monovalent silver sulfide. Arsenic was detected mostly in the form of di- and trivalent arsenic sulfides. Pentavalent arsenic oxide was identified only on the surface of the crystals and can be easily eliminated by ion milling.  相似文献