Electron Probe Analysis Research Articles

The Characteristics, Enrichment, and Migration Mechanism of Cadmium in Phosphate Rock and Phosphogypsum of the Qingping Phosphate Deposit, Southwest China

Sedimentary phosphate rocks are characteristically rich in organic matter, and contain sulfides and a high concentration of trace elements, including cadmium (Cd), which is harmful to the human body. The mining of phosphate rock and phosphogypsum at Qingping has expanded the release of Cd into groundwater and farmland soil. To prevent and control Cd pollution it is critical to reveal the carrier mineral phase(s) and migration mechanism of Cd and other elements in phosphate rock and phosphogypsum. The elemental and mineral composition of bulk samples were analysed by XRF, ICP-MS, and XRD, respectively. The results showed that from phosphate rock to phosphogypsum, the main constituent elements changed from CaO (49.43%) and P2O5 (36.63%) to CaO (33.65%) and SO3 (>34%), and the main mineral changed from fluorapatite to gypsum. Among all the elements, the element transfer factor (ETF) of P2O5, F, Co, U, Cd, and other elements was low; the ETF (Cd) was only 10.85%, and only a small amount of Cd entered the acidic phosphogypsum during the production process. Raman spectroscopy analysis revealed two types of apatite: the brown–black apatite with organic matter (type 1) and the yellow–light brown apatite without organic matter (type 2). LA-ICP-MS analysis showed that the Cd element content in type 2 was lower, while the organic matter and Cd element content in type 1 were higher, suggesting that Cd may be controlled by organic matter, and the relationship with apatite is not apparent. Electron probe analysis and XRD semiquantitative results show that the content of Cd in pyrite is higher (511 ppm), which is significantly higher than that of bulk rock. In addition, pyrite is rich in Co, As, Ni, Zn, and other elements. The content of Cd in phosphate ore shows a good correlation with that of pyrite. Cd in Qingping phosphate rock is mainly controlled by organic matter and pyrite, and only a small amount of Cd is transferred to phosphogypsum. Reducing the environment leads to the enrichment of Cd in phosphate rock.

SOME IMPORTANT CHARACTERISTICS OF POLYMETALLIC LEAD-ZINC ORE IN HAJVALIA MINE, KOSOVO

In this paper are presented general geological data for the polymetallic Hajvalia deposit. In particular, we have presented the scientific results regarding the chemical and mineralogical composition of sulfur mineralizations from the Hajvalia deposit. The distribution of the main metals used during the mining activity in this deposit has been studied with special emphasis. From the microscopic description of the mineral samples in the Hajvalia deposit, the following mineral compositions result: sphalerite, galena, pyrite, chalcopyrite, marcasite, arsenopyrite, pyrrhotite, tenanntite, as well as non-metallic minerals. The geochemical associations indicate the strong connection of Pb with Zn and Ag, and less with Cd and Cu. There is another association of Sb with Cd in antagonism with Cu, and an association of Bi with Cu in antagonism with As. Electron probe analysis shows that galena is quite pure with sporadic high content of Ag (up to 100 ppm). The Fe content in the sphalerite is quite homogeneous and varies from 9 to 11.5%, or 0.18 Fe atoms in the crystallochemical formula. As is known, the Fe content in sphalerite depends on the temperature of the mineral formation and, in some cases, can be used as a geothermometer. The main characteristic of galenites is their "purity", with a very high content of Pb. Ag stands out among the other elements, as does the presence of Hg, more Sb than Bi. The characteristic is the presence of Te and Se in isomorphism with S, always with a predominance of Te. In contrast to galena, the contents of Ag as well as Se and Te are lower while it is found more often in Bi than Sb.

Tracing the Source of Hydrothermal Fluid in Ophiolite-Related Volcanogenic Massive Sulfide Deposits: A Case Study from the Italian Northern Apennines

The Italian Northern Apennines contain several Fe-Cu-Zn-bearing, Cyprus-type volcanogenic massive sulfide (VMS) deposits, which significantly contribute to the Cu resources of Italy. The massive sulfide lenses and related stockwork mineralizations are hosted by several levels (from basalt to serpentinite) of the unmetamorphosed ophiolitic series; therefore, this region offers perfect locations to study the ore-forming hydrothermal system in detail. A combination of fluid inclusion microthermometry, Raman spectroscopy, electron probe analyses (chlorite thermometry) and stable and noble gas isotope geochemistry was used to determine the fluid source of the VMS system at Bargone, Boccassuolo, Campegli, Casali–Monte Loreto, Corchia, Reppia and Vigonzano. This question of the fluid source is the focus of modern VMS research worldwide, as it has a direct influence on the metal content of the deposit. The obtained temperature and compositional data are both in the typical range of VMS systems and basically suggest evolved seawater origin for the mineralizing fluid. Modification of seawater was most commonly due to fluid–rock interaction processes, which happened during long-lasting circulation in the crust. The role of a small amount of magmatic fluid input was traced only at the lower block of Boccassuolo, which may be responsible for its higher ore grade. This fluid origin model is evidenced by O, H and C stable isotopic as well as He, Ne and Ar noble gas isotopic values.

Differential precipitation mechanism of cement and its impact on reservoir quality in tight sandstone: A case study from the Jurassic Shaximiao formation in the central Sichuan Basin, SW China

Permeability heterogeneity of tight sandstone reservoir is mainly determined by the types and quantities of different cements and dissolution processes that occur during the burial. The thin section description, scanning electron microscopy (SEM), x-ray diffraction (XRD), cathodoluminescence imaging (CL), computed tomography (CT) scans, mercury intrusion tests, electron probe analysis, fluid inclusions and isotopic analysis were used to determine genetic mechanism and its impact on reservoir quality of differential cement combinations in Shaximiao Formation tight sandstone in the Central Sichuan Basin, China. Diagenetic minerals in the Shaximiao Formation (J2s) sandstone comprise calcite, laumontite, chlorite and dissolution. The pore space of J2s sandstone mainly comprises primary pores and secondary pores formed after mineral dissolution. The reservoir sandstones can be divided into six types according to different combinations of the laumontite, chlorite and calcite. Authigenic chlorite coating of J2s sandstones occurred via chloritization of smectite during eodiagenesis. Laumontite cements derived from transformation of volcanic rock fragments, were precipitated in a strong alkaline environment with high pH value (9.5–12) and abundant Ca2+, Si4+, Al3+ during eodiagenesis. The δ13C and δ18O isotopic values and petrological characteristics indicate that calcite cement was related to feldspar dissolution and decarboxylation of organic matter. The different cement combinations were determined mainly by the sedimentary facies and subsequent diagenetic environment evolution. Laumontite precipitation needs a stronger alkaline diagenetic environment than that for chlorite and calcite. The early chlorite coating provided sufficient remaining pore-space for pore-filling laumontite and calcite precipitation. The presence of pore-filling laumontite decreased space for calcite precipitation. However, laumontite is more readily soluble than calcite. The different cement combinations have distinct residual pore space combinations meaning that some intervals of rock have sufficient permeability to act as viable reservoir rock whilst other combinations do not.

In Situ Preparation of Nano-Cu/Microalloyed Gradient Coating with Improved Antifriction Properties

In order to solve the failure problem between the crankshaft and the connecting rod friction pair, nano-Cu/microalloyed gradient coating was prepared on the surface of the crankshaft by in situ gaseous nitriding process. Electron probe analysis confirmed the change of delamination after the in situ nitriding process, and the formed coating included three layers: the upper layer is a nano-copper layer, the middle is a microalloyed layer (containing Cu, N, and Fe elements), and the bottom is a nitriding diffusion layer. The change of profile hardness curve was analyzed by microhardness test. The bonding force between the coating and the substrate was analyzed by the scratch test. The friction and wear test showed that the nano-Cu/microalloyed coating could achieve the effect of antifriction. Moreover, self-lubricating and antifriction mechanisms of nano-copper coating were proposed. These results indicated that the in situ gaseous nitriding process could provide a new surface modification technique for the precision friction pairs.

Geochronology, geochemistry, Hf isotope, and electron probe analysis of the diorite in the Jianhei Mountain, East Kunlun Orogenic Belt, China, and their geological significance

Geochronology, geochemistry, Hf isotope, and electron probe analysis of the diorite in the Jianhei Mountain, East Kunlun Orogenic Belt, China, and their geological significance

Investigation of the process of sulfiding of gold-arsenic containing ores and concentrates

Purpose. Research of the removal of arsenic by sulfiding from gold-arsenic containing concentrates of the Bakyrchik deposit. Methodology. To determine the composition of the samples, chemical and electron probe analysis were carried out; to determine the phase composition of materials, X-ray analysis was conducted. In order to predict the process of sulfidation of arsenic and its compounds in the range of 2982000 K, a thermodynamic analysis was performed. To establish the optimal conditions for the process of sulfiding arsenic and its compounds, studies were carried out to determine the effect of temperature and the consumption of elemental sulfur on the degree of sublimation of arsenic from gold-arsenic concentrate. The sulfiding roasting of the concentrate was carried out with elemental sulfur vapor coming from a new design evaporator with a mixture of gaseous nitrogen. Findings. The main minerals of the original concentrate are pyrite, marcasite, arsenopyrite, native gold and silver. Significant elements in the concentrate are, %: arsenic 2.93.1, iron 707.3, gold 40. It has been calculated by thermodynamic analysis that when the main minerals of gold-arsenic containing refractory ores and concentrates interact with sulfur in a neutral environment and in the range of 5001000 C, reactions of formation and removal of arsenic in the form of sulfides As2S3 and As4S4 occur. When a new design evaporator supplies elemental sulfur in a mixture with neutral gas and with an increase in firing temperature from 700 to 850 C at S : As = 0.35 : 1, the degree of sublimation of arsenic increases from 94.7 to 98.2%, with FeS2 : As = 1.3:1 from 94.0 to 99.5%. With an increase in the consumption of elemental sulfur vapor (with an increase in the S : As ratio from 0.35:1 to 0.6 : 1 and a temperature from 700 to 800 C), the degree of sublimation of arsenic from the gold-arsenic product reaches up to 99%. The condensed sublimes contained up to 98.599% As4S4 and As2S3, the dust caught in cyclones is close in its composition to the composition of cinder. Originality. A new technology for the removal of arsenic from gold-arsenic containing concentrates in an oxygen-free atmosphere in the temperature range of 700850 C with the removal and capture of arsenic sulfides up to 100% is proposed. The regularity of the degree of sulfidation of arsenic and its oxidized compounds by elemental sulfur vapors in a mixture with a neutral gas to As4S4 and As2S3 has been established. Practical value. The use of the new technology makes it possible to completely convert arsenic into sulfide forms which are environmentally friendly, convenient for storage, burial, or for use as antiseptics. The development can be used for processing arsenic-containing polymetallic ore materials.

Hydrothermal Alteration and Its Superimposed Enrichment for Qianjiadian Tabular-Type Uranium Deposit in Southwestern Songliao Basin

The evolution characteristics of hydrothermal activity and superimposed uranium mineralization in the Qianjiadian ore field in southwestern Songliao Basin are still controversial and lack direct evidence. In this comprehensive study, a detailed identification of dolerite and hydrothermally altered un-mineralized sandstone and sandstone-hosted ore in the Yaojia Formation have been performed through the use of scanning electron microscopy observation, electron probe, carbon-oxygen-sulfur isotope, and fluid inclusion analyses. The results show that the hydrothermal fluid derived from the intermediate-basic magma intrusion is a low-temperature reducing alkaline fluid and rich in CO2, Si, Zr, Ti, Fe, Mg, Mn, and Ca, producing different types of altered mineral assemblages in the rocks, including carbonation, pyritization, sphalerite mineralization, clausthalite mineralization, silicification, and biotitization. Specifically, the carbonate minerals in sandstone are mixed products of deep hydrothermal fluid and meteoric water, with carbon and oxygen isotopes ranging from −5.2‰ to −1.7‰ and −20.4‰ to −11.1‰, respectively. Carbon source of the carbonate minerals in dolerite is mainly inorganic carbon produced at the late stage of intermediate-basic magma evolution, with carbon and oxygen isotopes from −16.1‰ to −7.2‰ and −18.2‰ to −14.5‰, respectively. Various carbonate minerals in the rocks may have been precipitated by the hydrothermal fluid after the magmatic stage, due to the change of its CO2 fugacity, temperature, and cation concentration during the long-term evolution stage. A series of carbonate minerals were generated as calcite, dolomite, ankerite, ferromanganese dolomite, and dawsonite. The precipitation processes and different types of carbonate mineral mixtures identified in this study mainly occur as parallel, gradual transition, interlacing, or inclusion metasomatism in the same vein body, without obvious mineralogical and petrologic characteristics of penetrating relationship. Homogenization temperature of fluid inclusions in calcite is high, in the range of 203–234 °C, with a low salinity of 0.71–4.34% NaCl, and the data range is relatively concentrated. Homogenization temperature of fluid inclusions in ankerite is usually low, ranging from 100 °C to 232 °C, with a high salinity of 4.18–9.98% NaCl. The precipitation processes of carbonate minerals and the results of this study are basically in consistent. Overall, the sandstone-type uranium deposits have a temporal and genetic relationship with hydrothermal activities during Paleogene. (1) Hydrothermal activity was directly involved in uranium mineralization, result in dissolution and reprecipitation of earlier uranium minerals, forming uranium-bearing ankerite and complexes containing uranium, zirconium, silicon, and titanium. (2) Hydrothermal fluid activity provided reducing agent to promote hydrocarbon generation from pyrolysis of carbonaceous fragments and accelerate uranium precipitation rate. (3) Regional water stagnation prolongs reaction time, contributing to huge uranium enrichment. This study provides new petrologic, mineralogical, and geochemical evidence for multi-fluid coupled and superimposed mineralization of sandstone-hosted uranium deposits in the sedimentary basin.

Stistaites of the South Urals

Research subject. Rare minerals of tin and antimony – stistaites from natural lead plates from the Severo-Svetlinskaya placer in the Chelyabinsk region and from microspherules of intermetallic compounds in the products of erosion of granites of the Kisegach complex in the Ilmeny Mountains.Materials and methods. Electron probe analysis and laser ablation with inductively coupled plasma were used to study the composition of the predominant minerals of intermetallic compounds in lead plates extracted during the washing of a gold-bearing placer, as well as from metal microspherules in the sandy fraction of eroded granites.Results. Two types of stistaite were identified: lead and arsenic-lead. Lead stistaites is sharply predominant, with its average composition (wt %) being Sb – 47.39, Sn – 38.75, Pb – 13.24, Cu – 0.06. The average composition of arsenic-lead stystaite (wt %) was found to be Sb – 43.89, Sn – 41.06, Pb – 11.02, As – 3.05, Cu – 0.47. Tin-lead microspherules from the destruction products of biotite granites of the Kisegach massif (Ilmeny Mountains) occasionally contain crystals and spotted precipitates of lead stistaite with the composition (wt %) of Sn 53.54, Sb 38.45, and Pb 7.42.Conclusions. It is assumed that, in both cases, the formation of alloys of intermetallic compounds of tin, lead and antimony with inclusions of native copper and iron was associated with granite magmatism.

Cooling rates and impact histories of group IAB and other IAB complex iron meteorites inferred from zoned taenite and the cloudy zone

AbstractMetallographic cooling rates of 10–20 K Myr−1 were obtained for four IAB iron meteorites from electron probe analyses of taenite and models simulating kamacite growth. Cooling rates were also determined for 21 irons in the IAB complex from the size of tetrataenite particles in the cloudy zone and a calibration curve using data for the four IAB irons and five other iron and stony iron groups. We find that the closely related IAB main group, low‐Au subgroups, Pitts grouplet irons, and San Cristobal cooled through 500 °C at 10–35 K Myr−1. The ungrouped IAB complex irons, Santa Catharina and Twin City, have bulk Ni contents of ~30 wt% and cooled much faster at ~200–1000 K Myr−1, most probably in a different parent body. Our cooling rates and observations allow conflicting interpretations of the nature of the low‐Ni phase in the cloudy zone to be reconciled. We infer that in fast cooled irons like Santa Catharina, the low‐Ni phase transforms to antitaenite, but in very slowly cooled meteorites like mesosiderites, martensite forms instead. In meteorites with intermediate cooling rates like IAB irons, the bulk of the cloudy zone probably contains antitaenite as the low‐Ni phase, but in the coarse region next to tetrataenite, martensite is present. Published isotopic ages show that metal–silicate mixing in group IAB irons occurred ~5–10 Myr after CAI formation, but the nature and timing of the impact are poorly constrained at present. Ar‐Ar ages testify to shock reheating of plagioclase during cooling over ~100 Myr. However, the cloudy zone is well preserved showing that metal was not heated significantly by shocks after slow cooling through 400 °C.

Origin of the Early to Middle Triassic polyhalite minerals in the Sichuan Basin, SW China: New evidence from calcium and sulphur isotopes and microfabrics

Polyhalite is a special potash fertilizer resource, which is widely distributed in the Triassic evaporite strata in the Sichuan Basin, but its genetic mechanism has always been controversial. This contribution presents new petrological, geochemistry, electron probe analyses, and Ca-S isotope systematics on Triassic polyhalite minerals for the first time from the Sichuan Basin aiming to better understand their origin. We present petrological observations of long columnar and granular polyhalites co-existing with halites (rock salt) and anhydrites that are not metasomatic in origin. Metasomatic polyhalites have also been studied, which have a fibrous and radial habit interwoven with anhydrite. The primary (sedimentary) polyhalite is solely formed from the evaporation of seawater, and the formation of metasomatic polyhalite involved impure meteoric water. The Ca and S isotopic values show that the sulphur and calcium in diamond-drillholes ZK001 and ZK601 are derived from seawater, whereas the sulphur and calcium in Well YS01 are derived from meteoric water. The sulphur and calcium in Well ZK02 are derived weathered terrigenous gypsum. This study demonstrates that the combined sulphur (δ34S) and calcium (δ44/40Ca) isotopes can be used to reveal the genesis of polyhalite.

СТРУКТУРООБРАЗОВАНИЕ ПРИМЕСНЫХ ПРЕЦИПИТАТОВ НИКЕЛЯ В КРЕМНИИ

In this study, using the method of electron probe analysis, the sequence of formation of various impurity precipitates of nickel in silicon in the process of diffusion doping at a temperature of T = 1573 K was investigated. The influence of the value of the cooling rate of the samples after diffusion annealing on the formation of impurity precipitates was considered. The morphological parameters of impurity precipitates of nickel in silicon have been revealed, and their chemical compositions have been determined. It was found that, depending on the size and shape, the nickel precipitates can have a single or multilayer structure

Оцінка зносу стрілчастих лап культиватора і технологія їх зміцнення

In recent years, research and developments related to the creation of new areas using nanotechnology take a special place in scientific achievements. They are developed and widely used in Physics, Chemistry, Biology, Electronics, Medicine, Food Production and to a much lesser extent in Engineering. This is due to the fact that there are different requirements to parts and products used in mechanical engineering, they have a complex shape, are made of different materials, production methods, heat treatment. While operating, their working layer undergoes degradation with a significant change in structure and their hardening using nanocoatings may turn out to be ineffective in both technical and economic aspects. In this case, only a specific approach, which is determined by comprehensive research with identification of the main factors of parts damageability in specific production and operation conditions, can be expedient. In addition, in some cases for hardening, repair and restoration of parts it is expedient to use surfacing methods with the introduction of modifying agents in a liquid bath during crystallization. These modifying agents are nano-and dispersed diamonds, which make it possible to adjust temperature parameters of crystallization, grain size, and stress level. This approach allows using high-alloyed, high-carbon electrodes even for thin-walled steel and cast iron products. In this case, the diamond inclusions additive plays the role of micro-refrigerators, which significantly change the crystallization temperature range. It is important to determine the optimal dose of the introduction of such a modifier and ensure uniform distribution the components in the coating. The presented work is devoted to the new technology development of hardening of cultivator blades metal with nano-and dispersed diamond additives, which are the part of the detonation charge from the disposal of ammunition. Nowadays, in agriculture, a large number of tillage implements are used for tillage, the working bodies of which are sweep blades. They are operated under conditions of abrasive particles impact, and this is accompanied by their intense wear with a corresponding change in the geometric dimensions of the main working surfaces. The worn sweep blades significantly reduce efficiency and quality of the carried-out work. The analysis of the effective choice of surfacing materials for hardening and improving their performance has been carried out and the nature of wear has been evaluated in order to identify areas of maximum damage and to determine the optimal method. It is known that T-590 and T-620 electrodes are used for the restoration surfacing of tillage implements. It was found the hardfacing of thin-walled parts is accompanied by a smaller heat sink and, in some cases, they are flooded with defect formation. To reduce it, a non-magnetic fraction of detonation charge from ammunition disposalin the form of an electrode modification was introduced, which ensured the uniform distribution the components in the coating. The method of the X-ray electron-probe analysis has been used to evaluate features of structure formation and component distribution along the perimeter of the coating. It was found out that this method of hardening reduces heat input and increases the microhardness and wear resistance of the surfaced coating, reduces the transition zone and thermal impact. The recommended method of metal hardening of new cultivator blades is to apply stripes on the point tip and wings of blades. On the basis of the nature of wear, the expediency of applying stripes on the point tip of the cultivator blade from the front side, and on wings from the rear side, is justified. The optimal geometrical dimensions of hardening stripes and their location on the blade are presented, which allows minimizing the local stresses and increasing wear resistance.

The Latowu Ultramafic Rock-Hosted Iron Mineralization in the Southeastern Arm Sulawesi, Indonesia: Characteristics, Origin, and Implication for Beneficiation

Latowu ultramafic block in the Southeastern Arm Sulawesi locally hosts elevated concentrations of Fe in addition to Ni. We investigated both host rock and mineralized samples' mineralogy and chemistry to find out mineralogical and chemical characteristics and interpret the iron mineralization process with beneficiation implications. The mineralogical nature of the samples was analyzed using optical microscopy and X-ray diffractometry (XRD) methods. The whole-rock and mineral chemistry analyses were performed using X-ray fluorescence (XRF) spectroscopy and electron probe microanalysis (EPMA) techniques. The analysis showed that the ultramafic rocks had been undergone a strong to complete serpentinization degree where lizardite appears to be the predominant mineral. Magnetite in this research comprised the principal iron-bearing mineral and functioned as discrete fine-grains and subhedral to anhedral crystals. Magnetite occurs as fragments in breccia, alteration rim in spinel, fine-grained disseminations, and micro veins. This research found that the whole-rock chemistry of an ultramafic breccia showed an elevated concentration in Fe2O3 with a grade of 28.44 wt%. Electron probe analysis of magnetite shows a wide variation of Fe ranging from 31.10 wt% to 67.20 wt%. It is interpreted that the formation of magnetite within ultramafic rocks is influenced by the hydration of primary minerals, mainly olivine. Iron is most likely released from olivine or pyroxene crystals during serpentinization, and the higher water content of serpentine promotes its mobility. It is suggested that the magnetic separation method can be potentially used to increase the Fe grade.

New data on the granite pedestal of the monument to Peter the Great “The Bronze Horseman” in Saint Petersburg

In order to expand and popularize knowledge about the stone decoration of Saint Petersburg, we present new data on the mineralogy and petrography of the famous Thunder-Stone, the parts of which were the basis for the monument to Peter the Great – the legendary “Bronze Horseman”. In the course of studying geological documentation of the monument's granite base, we examined the mineral composition and internal structure of granite, as well as the fragments of a pegmatite vein and veinlets found in it. 25 single-mineral samples were collected from the available micro-scaled shear fractures within the pedestal surface and studied by electron microscopy, electron probe and X-ray phase analysis. It was established that K-Na feldspar in the granite composition was represented by microcline, whereas micas were represented by annite-siderophyllite and muscovite. Accessory minerals included monazite, xenotime, thorite, zircon, rutile, apatite, fluorite, Ti-, Nb-, Ta-bearing minerals, uranium phosphates. The presence of topaz is characteristic of pegmatites. The revealed structural and textural features of four granite boulders in the monument pedestal, as well as mineralogical and chemical composition of their rock-forming and accessory minerals, showed the similarity of this rock to Precambrian biotite-muscovite granites and topaz-containing pegmatites (stockscheiders) of the late formation phase of the Vyborg rapakivi granite massif. The research results are considered as the basis for further geological and mineralogical study of the Thunder-Stone origin and determining the place of its separation from the primary source.

Relationship between Rockwell hardness and pearlite lamellar spacing of hardened layer under different cooling rates for U75 V 60 kg m−1 heavy rail

AbstractIn this study, the heat treatment processes for U75 V heavy rail were studied systematically. Further, a simple and convenient method for measuring pearlite average lamellar spacing in steel by electron probe analysis is introduced, which can make the results closer to the real pearlite average lamellar spacing. This method was used to measure the pearlite average lamellar spacing at different positions of rail head under different heat treatments. Furthermore, the relationship between pearlite average lamellar spacing and Rockwell hardness of U75 V rail steel was determined. This study will provide important theoretical guidance for the formulation of rail heat treatment processes and the measurement of pearlite average lamellar spacing in steel.

Characteristics and controlling factors of tuff tight reservoir in Tiaohu formation of Malang sag, Santanghu basin, China

Santanghu basin in Northwest China is a petroliferous basin. In recent years, researchers have discovered tuff tight reservoirs in the Tiaohu formation of Malang sag. Thin section, scanning electron microscopy, electron probe, X-ray diffraction, and CT scanning analysis are applied to reveal the petrological characteristics, physical properties, and pore texture of tuff tight reservoirs. Major controlling factors of the formation of high-quality tuff tight reservoirs are also discussed. The results show that the tight reservoir is intermediate-acidic crystal-vitric tuff. The main component of tuff reservoir is felsic vitroclastic, followed by crystal fragment and a small amount of bioclast, and trace clay content. Mercury injection and CT scanning show that the tight oil reservoir is characteristic of medium-high porosity, ultra-low permeability, and high oil saturation, which is controlled by its pore texture. There are four types of micropores in tuff reservoir, among which the principal reservoir space is devitrified micropores and crystal fragment dissolution micropores. Micropores are distributed universally in the tight oil reservoir, and the throat is nano-scale throat. It is considered that the tuff in the study area is formed by the deposition of volcanic ash in stable water after long-distance drifting in the air. The formation of high-quality tuff tight oil reservoir derives from 3 key factors: (1) shallow-semi-deep lacustrine environment, which is less affected by terrigenous input; (2) intermediate-acidic volcanic ash which forms the tuff reservoir; (3) devitrification and dissolution during the diagenesis.

Identification Characteristic of Turquoise Associated Mineral Crandallite-Goyazite

Recently, a kind of turquoise associated mineral has appeared on the market, which is very similar to turquoise in appearance. The authors studied a relevant sample by means of conventional gemmological tests and the other methods including thin-section observation, electron probe analysis, X-ray powder diffraction, infrared spectroscopy, Raman spectroscopy and ultraviolet-visible analysis, etc.The results showed that the main mineral component of the sample is crandallite and goyazite, as well as a certain amount of turquoise, etc. The main colour of the sample is blue, partially bluish green, and the blue colour is uneven, mainly enriched as dots or lumps. It has cryptocrystalline texture with the density of 2.52 g/cm3, and its refractive index is about 1.62 (point measurement). The infrared spectra of crandallite-goyazite show the main absorption peaks at 3 585, 3 420, 3 140, 1 320, 1 116, 1 039 cm-1 and 604 cm-1, and the Raman spectra of crandallite-goyazite show the main peaks at 1 104, 1 034, 987, 612, 518, 257 cm-1 and 185 cm-1, which are different from those of turquoise. Since it is difficult to identify this kind of turquoise associated mineral, conventional gemmological tests, Fourier infrared spectrometer, Raman spectrometer, X-ray powder diffraction analysis and electron probe analysis should be ultilized comprehensively.

BaFe[CO3]2, a new double carbonate: Synthesis, structural characterisation, and geostability implications for high and low PT

For the first time, a new ordered double carbonate, BaFe(CO3)2, was synthesized by a solid-state reaction between BaCO3 and FeCO3 at high pressure-temperature conditions (PT; 3 GPa and 700 °C). This finding adds a new so-far unknown member to the group of norsethite-structured carbonates, which is often used as a geochemical analogue for dolomite. Thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) reveal that BaFe(CO3)2 decomposes between temperatures of 450 °C and 880 °C, which is similar to norsethite (BaMg(CO3)2), but substantially higher than of pure FeCO3. The formation of BaFe(CO3)2 through solid-state reaction is evidently slower than that of BaMg(CO3)2 and BaMn(CO3)2 under the same experimental conditions. Using synthetic BaFe(CO3)2 powder as starting material, the reaction in the presence of CO2-bearing solution in contrast to water as a flux medium indicates the BaFe(CO3)2 instability at high PT conditions. The crystal structure and composition of the double carbonate were obtained using single crystal X-ray diffraction (XRD), Raman spectroscopy, and electron probe (EP) analysis. Two different types of the new double carbonate were identified: The experimentally derived phase belong to crystal structures that are related to the R3¯m and R3¯c space groups, respectively. The Raman spectra indicated that the difference is caused by a superstructure parallel to the c-axis. The charge and spin states of Fe in the new phases is determined using Nuclear forward scattering of synchrotron radiation. Furthermore, the thermodynamic properties of the double carbonate at standard conditions are estimated and a phase diagram is constructed depicting the stability field in low-temperature aqueous environments with these results being compared to natural aqueous solutions.

Study on geological characteristics and critical metal deportment of the Huangzhuyuan silver polymetallic deposit in Luzong basin, Anhui Province

黄竹园银多金属矿床位于长江中下游成矿带庐枞矿集区东南缘，是成矿带断凹区火山岩盆地内首次发现的浅成低温热液型银多金属矿床，亟待开展矿床地质特征、金属元素特别是关键金属的赋存状态和矿床成因研究。黄竹园矿床矿体主要赋存于下白垩统砖桥组、双庙组火山岩及断裂破碎带中，呈层状、似层状产出；矿石类型主要有脉状、浸染状、细网脉状。本次工作基于矿床地质特征研究，通过对矿床中采集样品进行手标本及室内镜下观察、短波红外分析测试（SWIR）、扫描电子显微镜（SEM-EDS）、电子探针分析（EPMA）和自动矿物综合分析（TIMA）等方法，阐明了矿床中的主要蚀变矿化特征和成矿期次，重点开展银和关键金属赋存状态及矿床成因类型研究。研究结果表明，黄竹园矿床总体表现出靠近矿体部位发育绢云母-伊利石化，向外围矿化较弱部位变为蒙脱石-高岭石化；根据不同的矿物共生组合及其相互关系，将矿床的成矿过程从早到晚分为无矿化石英脉阶段、石英-银矿物-硫化物脉阶段和石英-碳酸盐脉阶段，其中石英-银矿物-硫化物脉阶段为该矿床最重要的银、铜成矿阶段。主要的银矿物为自然银、硫铜银矿和硫汞铜银矿。矿床中的主要关键金属矿物为辉砷钴矿和铁硫砷钴矿，呈不规则粒状镶嵌在辉铜矿和黄铁矿边缘。通过黄竹园矿床与国内外其他浅成低温热液矿床地质特征对比，本次工作认为黄竹园矿床是高硫型浅成低温热液矿化叠加于斑岩型矿化之上的复合成矿的典型实例。通过与矿区北部钱铺酸性蚀变岩帽（<1km）之间对比研究，提出黄竹园-钱铺酸性蚀变岩帽地区可能存在一大型斑岩-浅成低温热液成矿系统，为庐枞盆地下一步深部找矿提供了方向。;Huangzhuyuan silver polymetallic deposit is located in the southeastern margin of Luzong volcanic basin in the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYB). It is the first discovered epithermal silver polymetallic deposit in the volcanic basin in the fault depression area of the MLYB. It is urgent to carry out a systematic study on the geological characteristics, the deportment of metals, especially critical metals, and the genesis of the deposit. Ore bodies are mainly hosted in the alteration zones and fractures of volcanic rocks of Zhuanqiao Formation and Shuangmiao Formation of Lower Cretaceous, as stratiform and lenses. Mineralization occurs as veins, disseminations and thin stockworks. Alteration and mineralization characteristics, mineral assemblages, especially the occurrence of Ag and critical metals and genesis of the deposit were discussed by hand specimens and microscopic observation, short wave infrared analyses (SWIR), scanning electron microscopy (SEM-EDS), electron probe analysis (EPMA) and TESCAN Integrated Mineral Analyzer (TIMA). The results show that Huangzhuyuan is characterized by muscovite-illite alteration of the ore body and montmorillonite-kaolinite alteration in the periphery of the deposit. The mineralization process of the deposit can be divided into three stage such as sulfide-barren quartz vein stage, quartz-silver-sulfides vein stage and quartz-calcite vein stage, of which quartz-silver-sulfides vein stage is the most important silver and copper mineralization stage. The main silver minerals are native silver, stromeyerite and danielsite. The main critical element minerals in the deposit are cobaltite and glaueodot, and are embedded in the margin of chalcopyrite and pyrite in irregular granular form. By comparing the geological characteristics of Huangzhuyuan deposit with other epithermal deposits globally, the Huangzhuyuan deposit is a porphyry-deposit overprinted by high sulfidation epithermal mineralization. By establishing relations with the surrounding Qianpu lithocap (less than 1km distance), it is indicated that there may be a large porphyry system in this area, and this indication provides a direction for further exploration in the deeper part of Luzong basin.