Особенности проявления контактового метаморфизма руд Ново-Учалинского месторождения на Южном Урале

The paper describes the development of a new movable modular plant for backfill preparation in underground mines. The plant has passed successful trials in the Uchalinsky Underground Mine (South Urals, Russia). This new plant may broaden horizons of mining industry modernisation in Russia. The commercial introduction of the proposed movable backfill preparation plant may help the mining of complex and low grade orebodies. The authors describe details and application of the movable modular backfill preparation plant.

Dental bleaching is a much requested procedure in clinical dental practice and widely related to dental esthetics. The literature is contradictory regarding the effects of bleaching agents on the morphology and demineralization of enamel after bleaching. The aim of this study was to analyze in vitro by scanning electron microscopy (SEM) the effect of hydrogen peroxide at 20% at neutral pH, cured by the green LED, to evaluate the action of these substances on dental enamel. We selected 15 pre-molars, lingual surfaces were sectioned and previously marked with a central groove to take the experimental and control groups on the same specimen. The groups were divided as follows. The mesial hemi-faces were the experimental group and distal ones as controls. For morphological analysis were performed 75 electron micrographs SEM with an increase of X 43, X 220 and X 1000 and its images were evaluated by tree observers. Was also performed quantitative analysis of the determination of the surface atomic composition of the samples through microanalysis with the aid of scanning electron microscopy. The use of hydrogen peroxide at a concentration of 20% at photoactivated green LED showed no significant changes in mineral composition of the samples or the dental morphological structure of the same when compared to their controls, according to the study protocol.

As more complex geological conditions are encountered in deeper underground mines, maintaining the safety and productivity of the mines has become more challenging. This requires installation of long-lasting high performance anchoring systems in underground mines. Cable bolts are particularly attractive for such applications since they have higher mechanical properties than conventional rockbolts and, being flexible, can anchor to greater depths into the rock strata. Despite substantial improvements in cable bolting technology over the years, catastrophic failure is still being reported. In this study, two failed cable bolts from an underground coal mine were collected and examined to identify their failure mechanism. Magnetic particle inspection, metallographic analysis and Scanning Electron Microscopy (SEM) were used to characterise the crack path and fracture surface of the wires from the failed cable bolts. A step-like crack path and Tearing Topography Surface (TTS) similar to those reported previously for failed reinforcing cables used as prestressed tendons in civil engineering structures were observed. These features indicated that the cable bolt failures were caused by Hydrogen Induced Stress Corrosion Cracking (HISCC).

Revalorization of degraded maguey pulquero substrate for Lycopersicon esculentum germination

Late hydrothermal veins exposed in the northern wall of the Novy peeble quarry are studied in a fenitic halo of the western contact of the Ilmenogorsk miaskite complex (South Urals) using scanning electron microscopy, Raman spectroscopy and X-ray diffraction. The veins fill open fractures, the walls of which are covered by feldspar clusters with chlorite-smectite crusts overgrown by calcite, pyrite and ilmenite. The final stage of the hydrothermal process is related to the formation of a zeolite assemblage with harmotome and clinoptilolite-Ca. The pyrite-ilmenite assemblage contains accessory columbite-(Fe), fergusonite-(Y) and syntactic intergrowths of minerals of the polysomatic bastnäsite-synchysite series (hydroxylbastnaesite-(Ce), parisite-(Ce), röntgenite-(Ce)), and hydroxyl analogs of parisite-(Ce), röntgenite-(Ce) and synchysite-(Ce). The Raman spectra of carbonates in vibrational region up to 1800 cm-1 are similar with previously published ones; the main bands are slightly shifted depending on a Ca/∑REE ratio. The assemblage of ilmenite, columbite-(Fe) and fergusonite-(Y) in late hydrothermal veins of the Ilmenogorsk complex is found for the first time.

The Novo-Uchaly volganogenic massive sulfide (VMS) deposit is one of the main ore objects currently being developed in the South Urals. It is a major source of copper and silver, the main source of zinc in Russia; along the way, Au is extracted, as well as a number of rare and critical/strategic metals (In, Co, Ni, Ga, Ge, Se, Te, etc.). During the field work, the authors collected a large set of samples taken from various areas of the ore deposit (footwall, hanging wall, wedging areas—the contact zone with host volcanites and dykes of gabbroids). Silver sulfosalts, cassiterite, and high-gallium mica (such as chlorite) and the fineness of native gold have been identified in ores for the first time using scanning electron microscopy and X-ray spectral microanalysis. The article describes the mineral associations of ores and new minerals identified by the authors. The results of mass spectrometry with inductively coupled plasma in combination with laser ablation (LA-ICP-MS) for minor elements in pyrite, sphalerite, and chalcopyrite from various mineral associations and samples from different parts of the ore deposit are presented. It was found that pyrite is the main concentrator of gold, selenium, and tellurium; their concentrations are especially high when local metamorphism occurs as a result of the temperature action of a thick gabbro dyke. Sphalerite contains high concentrations of cadmium and indium, as well as gallium and tin.

Contrasting provenance signals in Riphean and Vendian sandstones in the SW Urals (Russia): constraints for a change from passive to active continental margin conditions in the Neoproterozoic

This paper investigates the mineralogical and geochemical characteristics, as well as the possible sources, of gold, silver, platinum group elements (PGE), copper, and lead found in the beach sands along Egypt’s Mediterranean coast. Using scanning electron microscopy and electron probe micro-analysis, this study determines the morphology and micro-chemistry of separated grains to assess their economic potential and how various minerals respond to different transport distances. The analysis reveals that gold grains are of high purity (94.11 to 98.55 wt.%; average 96 wt.% Au) and are alloyed with Ag (1.28–2.32 wt.%) and Cu (0.16–3.15 wt.%). Two types of gold grains were identified, indicating differences in transport distances. Variations in morphology, surface features, inclusion types, rims, and chemistry of the native metals, including gold grains, suggest differences in composition, weathering degree, transport distance, deposit types, and host rocks. The average Ag concentration in gold grains (1.86 wt.%) suggests a link to mesothermal or supergene deposits. Most silver, copper, and lead grains are spherical, with some variations in shape. Silver grains have 71.66–95.34 wt.% Ag (avg. 82.67 wt.%). Copper grains have 92.54–98.42 wt.% Cu (avg. 94.22 wt.%). Lead grains contain 74.22–84.45 wt.% Pb (avg. 79.26 wt.%). The identified platinum group minerals (PGM) belong to the Pt–Fe alloys and sperrylite, both of which are PPGE-bearing minerals. These metals likely originate from the weathering of upstream Nile tributaries surrounded by igneous and metamorphic rocks from Ethiopian and Central African regions, with a minor contribution from the Egyptian Eastern Desert Mountains.

We study a class of problems involving the motion of a linear elastic body in frictional contact with a linear elastic half space. The dynamic effects considered are the inertial properties of the body regarded as rigid. We study only those regimes of contact interaction for which the slip velocity with the body taken as absolutely rigid and the time rate of change of the elastic displacements of points of the body and the half space that are on the contact surface are of the same order of magnitude. This work generalizes previous work on similar problems in that we simultaneously consider inertia forces of the body and the convective term in the slip-velocity due to the rigid-body velocity of the slider/indentor. Thus regimes of contact interaction investigated include rolling/sliding and shift-torsion type. We propose a variational formulation of the following two problems: (a) finite contact area and shift-torsion type of contact kinematics, (b) local contact area and general kinematics at the contact surface. Results for an elastic cylinder contacting an elastic half-plane are also given.

Optimal design techniques for kinematic couplings

Rock destruction under high‐temperature conditions is a key issue for nuclear waste treatment projects, underground coal gasification, and improvement of the use of geothermal energy for heating. Therefore, in this study, various methods and techniques were integrated to study the changes in mechanical properties, mineral composition, and microscopic fracture characteristics of Sichuan sandstone treated at 600°C. First, the fracture toughness and indirect tensile strength of untreated sandstones and high‐temperature treated sandstones were tested by the MTS testing machine, and the double‐K model (DKFM) was used to estimate the unstable fracture toughness. Then, the diffraction spectra of sandstone were analyzed with an X‐ray diffractometer to determine the mineral composition change after heat treatment. Finally, the microscopic features of sandstone were observed through a scanning electron microscope (SEM) and optical microscope. The results show the following. (1) There is no significant change in the tensile strength and fracture toughness of Sichuan sandstone treated at 600°C. (2) The brittleness of Sichuan sandstone decreases and the ductility increases after high‐temperature treatment. (3) The unstable fracture toughness value Kun obtained by the double‐K model (DKFM) is significantly larger than the apparent fracture toughness value Kif. (4) After treatment at 600°C, the clay minerals in the sandstone changed significantly. Kaolinite is dehydroxylated to metakaolinite, which may increase the ductility of the rock.

Water–rock interactions and scouring actions are recognized key factors that significantly influence the disintegration of rock on the surface of slopes. However, the research on rock disintegration, specifically under the action of scouring, is limited, which makes it difficult to understand the characteristics of rock disintegration. Therefore, in this study disintegration tests were performed on the gypsum karst breccia collected from the Zhoukoudian site in Beijing, using a self-made disintegration test device. Further, this study investigated the impact of solution pH, flow velocity, and the number of cycles on the characteristics of rock disintegration. The changes in pore structure, microstructure, and mineral composition of the rock were analyzed using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma optical emission spectrometer (ICP-OES) methods. The findings reveal that the cumulative relative disintegration amount of the gypsum karst breccia experiences an increase as the pH value of the soaking solution decreases and the number of cycles increases. Once a specific flow rate is attained, the cumulative relative disintegration amount stabilizes (about 73%) and no longer exhibits significant changes. This phenomenon signifies the presence of a stabilizing flow rate for disintegration. The stable flow rate concerning rock disintegration is influenced by both the solution’s pH and the number of cycles. Following acid contamination, the rock sample’s particle morphology undergoes disruption, leading to the dissolution of cement. This, in turn, leads to an augmented release of Ca2+, Al3+, and Ma2+ ions in the solution, intensifying the disintegration of the rock samples. Conversely, alkali contamination prompts secondary cementation, mitigating localized damage. This results in a marginal increase in the calcite content within the rock samples (from 15.3% to 19.2%), while the release of Ca2+ in the solution experiences a decrease. Additionally, there is a slight increase in the release of Al3+ (a maximum increase of 1.71 mg/L), which minimally inhibits the disintegration of the rock samples. Notably, the rock disintegration predominantly occurs around macropores, and the effect of solution pH on the disintegration characteristics and stable flow rate is primarily due to the changes in the relative proportion of macropore volume in the rock samples. The findings of this study have significant implications for the prediction and control of slope-related issues.

Eclogites from the North Qilian suture zone are high-pressure low-temperature metamorphic rocks of ocean crust protolith, and occur in both massive and foliated varieties as individual blocks of tens to hundreds of metres in size. The massive type is weakly deformed and shows granoblastic texture characterized by a coarse-grained peak mineral assemblage of Grt1 + Omp1 + Ph + Rt ± Lws (or retrograde Cz). In contrast, the foliated type is strongly deformed and shows a fine-grained retrograde mineral assemblage of Grt2 + Omp2 + Cz + Gln + Ph. Both total FeO and aegirine contents in omphacite, as well as XFe[=Fe3+/(Fe3+ + AlVI)] in clinozoisite/epidote, increase significantly from massive to foliated eclogites. Lattice preferred orientation (LPO) of omphacite, determined by electron back-scatter diffraction analysis, is characterized by weak and strong SL-type fabrics for massive and foliated eclogites, respectively. Clinozoisite/epidote also developed SL-type fabric, but different from the LPOs of omphacite in and axes, owing to their opposite crystallographic long and short axis definitions. The transition of deformation mechanism from dislocation creep to diffusive mass transfer (DMT) creep in omphacite and the concomitant retrograde metamorphism both are efficiently facilitated when the original coarse-grained Omp1 + Grt1 + Lws assemblage is dynamically recrystallized and retrogressed into the fine-grained Fe3+-rich assemblage of Omp2 + Grt2 + Cz + Gln. The DMT process with concomitant anisotropic growth assisted by fluids is considered to be an important deformation mechanism for most minerals in the foliated eclogite. P–T estimates yielded 2.3–2.6 GPa and 485−510 °C for the massive eclogite and 1.8–2.2 GPa and 450−480 °C for the foliated eclogite. The significant increase in total Fe and Fe3+ contents in omphacite and clinozoisite/epidote from massive to foliated eclogite suggests changes in mineral compositions accompanied by an increase in oxygen fugacity during ductile deformation associated with exhumation. The LPO transition of omphacite, clinozoisite and rutile from weak SL-type in massive eclogites to strong SL-type in foliated eclogites is interpreted to represent the increment of shear strain during exhumation along the ‘subduction channel’.

40Ar/39Ar dating of poly-orogenic rocks: an example from the Cap de Creus peninsula (Eastern Pyrenees, Spain)

Four deep-sea manganese nodules and one fossil nodule from Timor have been analysed for 45 elements (major elements, rare earths and precious metals) by X-ray fluorescence, spark source mass spectrometry and neutron activation analysis. Co-existing sediments from two nodule sites in the Southwestern Pacific Basin have also been analysed. Differences in nodule composition are apparent, particularly for the Timor nodule. The trace metal compositions of this nodule, however, reveals it to be a typical deep-sea nodule, although some element redistribution has clearly taken place since exposure of the nodule on land. The distribution of a number of elements including Tl, Ir, Pd, Au and the rare earth elements between deep-sea nodules and their associated sediments appears to be dependent on a number of factors including the major element composition of the nodule (e.g. dilution by the silicate phase of the nodule), the differing stability of various element complexes in seawater, and the influence of differences in redox states on complex stability. Au and Si, on the other hand, are positively correlated in nodules and sediments possibly because they have a common source, either submarine detritus or basalt-seawater interaction. The rare earth contents of the sediments from the N.E. sector of the Southwestern Pacific Basin are high compared with previous determinations of rare earths in marine sediments and show no evidence of Ce depletion relative to La on a shale-normalised basis. These high contents reflect the well oxidised conditions and low sedimentation rates of this environment.