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In areas with cold climate seasonal snowpack is an attractive sampling material for geochemical exploration of deep mineral accumulations. However, previous studies on assessment of exploration efficiency of snow cover have paid little attention to snow composition variability conditioned by local landscape structure. The layered sampling of snow sections was performed in different landscape settings of the local area. The research area is characterized by the absence of ore mineralization zones and low anthropogenic load. The physical-chemical parameters and concentration of wide range of elements were identified in snowmelt. Multi-component data was integrated by means of factor principal component analysis. Besides, additive and differential geochemical indexes were used. The classification snow models were developed using hierarchical cluster analysis. The variance of chemical elements distribution and factor models of geochemical pattern were compared before and after reduction of background fluctuation. In terms of variation coefficient values of chemical elements the area has background parameters of chemical inhomogeneity. In total variance a lateral component prevails over a vertical one. The highest concentrations of chemical elements were found in snow section of forest landscape. It is necessary to take into account the fact of geochemical background fluctuation when interpreting the data of metal assay snow survey. After the reduction of lateral geochemical background fluctuation, the factor model has better classified the chemical elements in terms of their connection with soluble and insoluble occurrence forms. The values of differential index of liquid and solid phases have a similar satisfactory vertical variability in different landscapes. The analysis of chemical elements concentration reveals snow horizons that were or are affected by thaw and percolating water. The snow bottom layer, which is sampled at geochemical exploration, is not strong influenced by elution. • Background chemical inhomogeneity of snow should be taken in exploration. • The variance of geochemical pattern depends on the landscape. • The effect of local aeolian matter is significant. • It is necessary to take into account elution of sampled horizon. [ABSTRACT FROM AUTHOR]

In geochemical exploration, the seasonal snow cover is a convenient natural material for identifying under deep covered mineral accumulations. Snow has shielding and accumulating properties sufficient for the occurrence of dispersion of geochemical halos. The snow horizon of geochemical sampling is protected from atmospheric and landscape factors of replenishment of its chemical composition for most of the winter. The filtrate of snow melted water is cleaned of large-sized solid material, and chemical compounds are in the dissolved and finely dispersed solid phase of submicron dimension. Therefore, in terms of the physical and chemical properties of the analyzed substance, snow geochemical survey is close to selective methods. Test surveys were carried out on single profiles of snow sampling at two ore occurrences (Au, Pb-Zn) and an oil field within the West Siberian plate. Concentrations of a wide range of chemical elements in snowmelt water filtrate were determined by the ICP-MS method. As a result of statistical processing of geochemical data, a low variability of concentrations of chemical elements has been established. Correlation and regression analyzes demonstrate the presence of linear dependences in the distribution of trace elements, which reflect the ability of elements to form easily soluble and hardly soluble occurrence forms. The variability of the local geochemical background is mainly due to the content of hardly soluble phases that entered the snow layer during its deposition on the ground. Presumably, they are represented by particles of aeolian dust, needles and scales of tree bark captured by snow from tree and shrub crowns. In the area of study with high heterogeneity of elementary landscapes, the influence of this factor is comparable in amplitude to the contrast of superimposed geochemical halos. Normalization of the concentrations of trace elements by the sum of rare earth elements (REE) allows to strengthen the useful geochemical signal. Geochemical anomalies detected in snow in space quite accurately coincide with the position of mineral deposits buried the platform cover terrains, and also find confirmation in the chemical composition of soils and soil air. The good potential of snow metallometric surveying for prospecting of deep-seated mineral resources needs to be confirmed by studying the vertical and lateral migration of chemical elements in the snow cover. • Geochemical snow survey is informative when searching for buried mineral resources • Correlation associations of chemical elements indirectly reflect their easily soluble and hardly soluble occurrence forms • The concentration levels of rare earths are associated with the introduction of soil particles into the snow • Normalizing the concentrations of trace elements by the amount of REE is useful for mapping of superimposed halos [ABSTRACT FROM AUTHOR]

The voltage and temperature dependence of post-breakdown (BD) conduction in SiO2 non-volatile memory bitcells is investigated. A model for charge transport in disordered systems is adapted to describe conduction through the BD path. The model uses a 2-D network of the quantum point contacts (QPCs) to simulate the oxide, and successfully reproduces the characteristics of experimental post-BD current in a large set of devices. Importantly, the temperature dependence in this model arises from the Fermi function rather than the structural changes in the oxide as suggested by previous studies. Once the QPC network model is fit to the experimental current–voltage ( $I$ – $V$ ) characteristics at one temperature, it is shown to correctly predict the $I$ – $V$ behavior at other temperatures without any additional parameters. Experimental $I$ – $V$ data from 100 devices that experience progressive BD are fit using the QPC network model, and for comparison, also using a single QPC model. We conclude that a QPC network gives a more realistic description of post-BD conduction than the single QPC model, as the network includes multiple path conduction and correctly describes the temperature dependence. [ABSTRACT FROM PUBLISHER]

[Display omitted] • The ore process within the SED was closely related to zones of tectonism, ring-shaped and radial faults, and acidic alteration. • The ore processes within the SED proceeded in 3 stages: barren alteration, sulfides with Au, finally supergene. • Two types of gold mineralization are distinguished: Au-Ag-telluride and Au-Ag. • The hypogene sulfide assemblage of SED is typical for intermidiate sulfidation signatature. • The abundance of alunite and other sulfute minerals defines the SED as an HS-IS type deposit. The Svetloye epithermal district (SED) is located within the Okhotsk-Chukotka volcanic belt (OCVB), 220 km southwest of Okhotsk. The OCVB, which formed during the Cretaceous with ore potential, is a large marginal volcanic rock belt associated with continental subduction. Svetloye occupies two volcanic edifices of different ages – the northwestern volcanic center (including the Emmy deposit) consists of basaltic-andesite of the Khetanian suite (Coniacian-Santonian time (K 2), and the southeastern volcanic center (hosts the Elena, Tamara, Lyudmila, and Larisa deposits) comprises the dacite-rhyolite-leucogranite formation of the Urak suite (Campanian-Maastrichtian time (K 2). Distinct host rocks and different levels of erosion in the two edifices of Svetloye led to various altered rocks, mineral assemblages, and diverse types of gold mineralization. The alteration halo of the Emmy deposit contains vuggy residual quartz, with Au-Ag-telluride and Au-Ag mineralization plus other tellurium-bearing minerals (goldfieldite, kawazulite, coloradoite, melonite, altaite, tellurobismuthite, tellurantimony, and native tellurium). Altered rocks of the other deposits are characterized by variable halos, including vuggy residual quartz, alunite, dickite, quartz-alunite-dickite, illite-chlorite, illite, illite–smectite, smectite, quartz-carbonate, and quartz-white mica alteration, hypogene and supergene processes. The hydrothermal (hypogene) and supergene ore processes within the SED occurred in 3 stages: leaching and barren quartz-rutile-pyrite zone with halos of quartz-alunite-dickite-pyrite (or quartz-illite-chlorite-calcite-pyrite), then quartz-pyrite with polysulfides and gold, gold-silver telluride, and finally supergene with 'mustard' gold. The alteration halo, epithermal ore bodies as hydrothermal veins and breccias with vug infill, colloform, and crustiform textures, hypogene sulfide assemblage represented by galena, sphalerite, tennantite-tetraedrite, and chalcopyrite of SED are typical of epithermal styles with an high-intermediate sulfidation signature, possibly indicates a porphyry deposit at depth. The lack of high-sulfidation-state sulfides such as hypogene covellite, enargite, famatinite, luzonite in the residual quartz may be due to their erosion at shallower paleodepth, and/or to their supergene oxidation below the present day surface. [ABSTRACT FROM AUTHOR]