Quartz Type Research Articles

A case study of the Yanshanian fluorite mineralization in South China: Fluid inclusion, element and isotope geochemistry and zircon U-Pb geochronology of the Kantian fluorite deposit in southern Jiangxi Province

The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H2O, with minor C3H6. Isotope analysis indicated δDVSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18OVSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H2O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit.

Ore-Forming Fluids of Orogenic Gold Deposit In Tamilouw-Haya, Seram Island, Indonesia

The Tamilouw-Haya orogenic gold deposit is located in the southern arm of Seram Island, Indonesia, occupying Tehoru Metamorphic Complex. Gold mineralization is predominantly in the form of veins, stockwork, and breccia, although minor dissemination is slightly appeared in the rock float samples. Ore-mineral assemblages are dominated by native gold, pyrite, chalcopyrite, sphalerite, tetrahedrite-tennantite (sulfosalt), galena, pyrrhotite, marcasite, realgar, kalininite, and arsenopyrite. Covellite, hematite, goethite, and malachite appear as supergene minerals. High-grade gold ores in this area are generally found in quartz-carbonate veins with the main alteration processes involving silicification, carbonatization, and sericitic. The P-T history of the mineralization was revealed by fluid inclusions, and this study implies the depth of ore deposit and its evolution during mineralization. The primary fluid inclusions from three different types of quartz/quartz-carbonate veins in Tamilouw-Haya crystallized at the homogenization temperature (Th) of 240 °C to 340 °C, with a fluid salinity from 3.87 to 0.70 wt. % NaCl equivalent, and melting temperature (Tm) of -0.4 to -2.3 oC. The ore-forming fluids consist mainly of two-phase (VCO2+LH2O) liquid-rich aqueous inclusions, characterized by low to rich CO2, low salinity, and moderate temperature. There are three vein types as the ore-bearing fluids with precious metals and anomalous high basemetal contents. Quartz type 1- veins (V1); concordant veins, formed at a temperature of 240-307 oC with an average salinity of 1.8 wt. % NaCl equivalent. Quartz type 2- veins (V2) tend to cut the rock foliation which are formed at temperature range from 293-336 oC with the average salinity that shows a value of 2.4 wt. % NaCl equivalent. Meanwhile, type 3 quartz-carbonate veins (V3) are formed at the temperature range of 240-340 oC and the average salinity of 2.72 wt. % NaCl equivalent. These quartz-carbonate veins cut the wall-rock foliation, which is identified as the late stage and associated with ore deposition in Tamilouw-Haya. The gold deposit in Tamilouw-Haya is formed at a depth of about 5.5-9 km of paleosurface, and the pressure between 1.7-2.4 Kbar in epizonal to mesozonal zones. Keywords: Tamilouw-Haya, orogenic gold, fluid inclusion, microthermometry, ore-forming fluids

Watch winder based on the internet of things

Watches are wearable devices that support human activities as timepieces. There are two types of watches based on their source driving energy: the quartz type, which uses a battery, and the automatic mechanical type, which uses a mechanical mechanism to convert the kinetic energy obtained when the clock is used as the energy to drive the hands. Automatic mechanical type watches have a time limit of 48 hours or two days until the energy turns off and the time stop. Therefore, a watch winder is needed to make movements to keep the automatic watch running while not in use. So, users can use their watch again without the need to adjust the time, date and other functions. The watch winder produced in this study employs a stepper motor that is controlled by an ESP32 microcontroller via a ULN2003 motor driver integrated circuit (IC). This type of stepper motor is used because it has a high rotor rotation precision to prevent the clock from over-winding problems. This watch winder device also has a watch condition monitoring feature through application-based temperature and humidity parameters. Users can monitor the condition of their watch and control the dial of the watch winder’s modules through the integrated application.

Magnesiothermic Reduction of Natural Quartz

In the current work, the metallothermic reduction of natural quartz by magnesium has been studied at 1373 K under different reaction conditions, i.e. quartz type, quartz particle size, Mg:SiO2 mole ratio and reaction time. The microstructure of reaction products was studied to illustrate the reaction progression through scanning and transmission electron microscopy techniques. X-ray diffraction analysis with Rietveld phase quantification was used to calculate the change in the amount of phases at different reaction conditions. The results showed that the Mg:SiO2 mole ratio strongly affects reaction mechanism and product characteristics such as phase content and microstructure. At lower Mg:SiO2 mole ratios, the reaction rate is fast at the beginning and the formation of a product layer consisting of different phases such as MgO, Si, Mg2Si, Mg2SiO4 and MgSiO3 around quartz particles limits the Mg diffusion. This phenomenon is more noticeable for larger quartz particle sizes where Mg should diffuse longer distance towards the quartz core to react with it. At higher Mg:SiO2 mole ratios, a significant amount of Si–Mg liquid alloy is formed during reaction where the high mobility of Mg in this liquid phase and cracking of quartz particles result in significantly higher reaction rate. Here the formation of intermediate phases is not significant and the products would be the mixture of MgO, Mg2Si, and either Si or Mg phases.

Provenance of quartz grains from soils over Quaternary terraces along the Guadalquivir River, Spain

The characterisation of quartz grains’ chemical and mineralogical properties in sediments and sedimentary rocks is widely used in provenance studies. This paper analyses quartz grains from the coarse sand fraction in soils in Quaternary fluvial terraces (Guadalquivir River, southern Spain). The tentative soil ages are 0.3 ka (Haplic Fluvisol), 7 ka (Haplic Calcisol), 70 ka (Cutanic Luvisol), 300 ka (Lixic Calcisol) and 600 ka (Cutanic Luvisol). The quartz grains analyses shed light on the sedimentological history of these terraces. Scanning electron microscope cathodoluminescence (SEM-CL) characteristics, micro inclusion inventory established by Energy-dispersive X-ray spectroscopy (SEM-EDX) and trace element contents determined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of quartz grains permitted distinguishing six types of grains in the soils studied: metamorphic quartz (type 1), undeformed granitic quartz (type 2), strongly altered granitic quartz (type 3), recrystallised (deformed) granitic quartz (type 4), sandstone-derived quartz (type 5) and hydrothermal quartz grains (type 6).Metamorphic quartz grains (type 1) come from the Sierra Morena (Iberian Massif) and Sierra Nevada (Internal Betic Zone). Granitic quartz grains (types 2 to 4) come from Los Pedroches batholith and its associated plutons (Santa Elena and Linares). The sandstone-derived quartz type 5 comes from the numerous sandstone outcrops scattered in the central catchment area of the Guadalquivir River. Finally, hydrothermal quartz grains (type 6) originate from hydrothermal veins associated with subvolcanic rocks of the Los Pedroches batholith.Variations were noted in the proportions of quartz types in soils of different ages, attributed to spatial and temporal changes in the catchment area. The most remarkable change occurred between 500 and 240 ka ago when the catchment area extended into Sierra Nevadás metamorphic rocks, well reflected in type 1 content (lower in P2, P4, P5 and PM) and their characteristics (quartz with less healed fractures, less Al content, bigger mica microinclusions, smaller Al/Ti ratio) in the post-500–240 ka soils.Our study shows that the combined study of SEM-CL characteristics, micro inclusions (SEM-EDX), and trace element contents (LA-ICP-MS) of quartz grains is an efficient approach for characterising the provenance of quartz grains in the sand fraction of soils.

Study of a Newly Discovered Microliths and Rock Art Site, Badedev Rakseha at Panna District of Madhya Pradesh, India

The literary data revealed that the Panna district of Madhya Pradesh has not been explored extensively in the context of prehistoric archaeology. Therefore, present study is considered, keeping in view for the same. For this purpose, a systematic exploration of Panna district was conducted during seasons 2019–20. After exploration, a rock art and microliths assemblage site, Badedev (24°45’41.80” N 80°17’2.73”E), Rakseha was discovered at Panna district by the first author and recovered around 500 Microliths assemblages and 02 rock shelters with depiction of paintings. The major type of microliths artefacts identified are; core, flake, blade, bladelets, scraper, lunate, borer, burin, points, triangle, and debris. The typo-technological and morphological analyses of assemblages revealed that various types of stone artefacts used by prehistoric group of this area were made on locally available raw material and they have a sound knowledge of durability of raw material used for tool making, as we have identified more than 36% and 30% of agate and quartz type of microliths respectively among the whole artifacts collected, as both of these are hard as well as durable type of stones. Remains of microliths assemblages and debitage stone material also certified that Badedev prehistoric site was a tool manufacturing site at this area. In rock paintings, themes are most dominantly zoomorphic figurine, human figurine, handprints, and geometric and non-geometric design. For detail study of pictographs DStretch software was utilized. On the basis of rock art style, color, composition, technique, theme, subject matter; motifs such as hunting scenes and large number of animal groups, it is assumed that this site was inhabited by hunter-gatherer group. Finally we are in position to say that the discovery of prehistoric site Badedev Rakseha enhanced our knowledge about the prehistoric culture of central Indian region.

Quartz types in the Wufeng-Longmaxi Formations in southern China: Implications for porosity evolution and shale brittleness

Quartz is an important component of shale and has a significant influence on shale physical properties. However, the specific effects that different quartz types exert on shale porosity evolution and brittleness remain unclear. A series of experiments including petrographic observations, geochemical analyses, and triaxial compress experiments were conducted on shale samples from the Wufeng-Longmaxi Formations in southern China. The Wufeng-Longmaxi samples have been classified into siliceous shale, argillaceous shale, and mixed shale. Several quartz types were identified in the shale samples, including extrabasinal detrital quartz and authigenic quartz (microcrystalline quartz, quartz overgrowths, and bioclastic quartz). Based on the different origins, the authigenic quartz was divided into biogenic quartz derived from the dissolution of siliceous organisms and S–I quartz derived from the conversion of smectite to illite. Bioclastic quartz, most microcrystalline quartz, and most quartz overgrowths are biogenic quartz. A small number of quartz overgrowths and microcrystalline quartz are S–I quartz. The quartz content of different genesis processes was quantitatively calculated using major and trace elements data collected via XRF. Quartz types in siliceous shale samples are dominated by biogenic quartz (avg. 49%). Extrabasinal detrital quartz is the primary quartz type in argillaceous shale samples (avg. 68%) and mixed shale samples (avg. 50%). Porosity reduction mechanisms in most of the Wufeng-Longmaxi shale samples are primarily compaction-dominated. Biogenic quartz acts as a pore protector rather than destroyer, while S–I quartz derived from the conversion of smectite to illite acts as a pore destroyer rather than protector. The brittleness index (BI) of siliceous shale samples is the highest of all the shale samples since the abundant biogenic microcrystalline quartz particles dispersed within the shale matrix connect rigid grains to form an interconnected force framework.

Нерудні мінерали прожилково-вкрапленої мінералізації у відкладах Кросненської зони Українських Карпат (район нового Бескидського залізничного тунелю)

The construction of the new Beskydy railway tunnel, which revealed the indigenous deposits of the Krosno formation of the Ukrainian Carpathians, provided an opportunity to obtain new results from the study of another prospective oil and gas-bearing areas of the flysch formation within the Krosno structural-facies unit. There is a second tunnel in length in Ukraine and passes under the Verkhovyna watershed ridge of the Ukrainian Carpathians. Its section is represented by the rocks of the Krosno formation, namely the stratification of sandstones, argillites and silt stones. There are two fracture zones have been indentified here, in which developed veinle-impregnated mineralization of ore (sulfides) and non-ore (calcite and quartz type of the “Marmarosh diamonds”) minerals. Calcite and quartz formas monominerals veins and in paragenesis calcite-quartz type of the “Marmarosh diamonds” ‒ sulfides. Quartz occurs in the form of splice sand well-faceted crystals, transparent, in yellow, brown, black, green colour. Calcite of a milky, translucent colour in the form of veins, veinlets, impregnation, powder on quartz, druz. Contains significant impurities of magnesium, manganese and iron which means the presence of a rhodochrosite-magnesite-siderite component. Hydrocarbon fluids are present in all calcite and quartz crystals of the “Marmarosh diamonds” type. By chemical composition, it is methane with impurities of higher hydrocarbons (up to hexane). Sometimes the manifestations of the outflow of a black substance with the smell of oil from the cracks in the veinlet-impregnated mineralization are recorded studied rock complexes of the flysch formation of the Krosno zone of the Ukrainian Carpathians (construction area of the new branch of the Beskydy railway tunnel), which acquires an important genetic significance.

Preliminary Study of Microwave Irradiation Towards Oil Palm Empty Fruit Bunches Biomass

In this study, torrefaction via microwave irradiation was introduced towards oil palm empty fruit bunches (EFB) samples. The samples of 10 g was fed into the quartz type crucible inside the microwave with the power input limit to 385 W. Continous nitrogen up to 50 ml/min were induced and promoted the non oxidative atmosphere in the closed crucible. This proved the increased of energy properties as high 23.6 MJ/kg for torrefied samples comparable to raw 14.8 MJ/kg. On the result of proximate analysis, fixed carbon shows the increase trends whereby the volatile matter decreased. Torrefaction has been found to improve the energy properties of oil palm EFB biomass as a fuel.

Lithofacies and petrography of Miocene Murree Formation, Peshawar basin, NW Pakistan: implications for provenance and paleoclimate

The Miocene Murree Formation is an enormous sedimentary deposit and is considered as foreland basin sediments of Himalayas, extending EastWest throughout the foothills of Himalayas. Lithofacies analysis was performed to establish the depositional environment, the following lithofacies were identified: clast-supported massive gravel (Gcm), sandstone with planar cross lamination (Sp), sandstone trough cross lamination (St), sandstone with horizontal lamination (Sh), sandstone with ripple cross lamination (Sr), sandstone with low-angle cross lamination (Sl) and mud and silt massive with roots bioturbation (Fr). These lithofacies depict shallow channel depth, deposition on the distal part of point bar, natural levees and flood plain of a meandering river. The modal composition data indicates that the Murree sandstone is arkosic to lithic wacke. The mineralogical and textural data suggests that sandstone is compositionally submature to immature and texturally immature to submature. The debris of rock fragments proposes diverse sources for Murree Formation. The ternary plots of detrital quartz type of the current study designate plutonic provenance. The high percentage of unstrained monocrystalline quartz (Qnu) relative to undulatory monocrystalline quartz (Qu) and polycrystalline quartz (Qp) proposes plutonic source area for Murree Formation. The paleoclimate plot discloses semi-humid–humid environment.

Characterization of fly ash solid-waste for low-cost insulation refractory bricks

Fly ash from Barsingsar, Bikaner thermal power plant in northern India, is significantly generating solid-waste. In India, coal is of poor quality having high ash content around 30–45 wt%, fly ash created at coal thermal power plants. The present work investigates the possible use of fly ash solid-waste for the research of insulation refractory bricks. Fly ash is considered as a powdered material being collected by dust collectors built-in boilers of thermal power plants with the use of coal as a fuel. The chemical, thermal, crystallographic and morphological analysis of fly ash solid-waste has been determined by XRF, DTA-TG, XRD and SEM, respectively. The XRF results show the fly ash solid-waste is alumina and silica-rich. XRD results also reveal that the material is composed of mullite and quartz crystals. SEM investigation exhibits the morphology of fly ash solid-waste is needle-like mullite and fibrous-like quartz type of structure, which supports the XRD results. It can be concluded from the inquiry that fly ash solid-waste is the potential low-cost raw material for insulation refractory bricks.

Ore-forming fluids of the Fancha gold deposit, Lingbao, Henan Province

The Fancha gold deposit is a representative of the auriferous quartz vein type gold deposits in the Xiaoqingling gold district where the ore-forming fluid is one of the key controlling factors in the deposits formation, and also the main focus of ore deposit research. Here, the geological characteristics and fluid inclusions of the Fancha deposit are presented in detail, with a description of the potential origin and evolution of the fluid and the genesis of the deposit. Field investigation and petrographic observation show that ore-bodies in the Fancha deposit are preferentially hosted in the amphibolites of the Taihua Group and are controlled by brittle fracture. Hydrothermal alteration in the Fancha deposit includes silicification, potash feldspathization, sericitization, pyritization and carbonatization. The mineral assemblage, cross-cutting and replacement relationships indicate that the ore-forming process can be divided into quartz-K-feldspar (I), quartz-coarse pyrite (Ⅱ), quartz-fine pyrite (III), quartz-polymetallic sulfide (IV) and carbonate stages (V). Gold is mainly precipitated in stages III and IV. Three types of fluid inclusions have been identified in the Fancha deposit, based on their characteristics at room temperature: three-phase CO2-rich, three-phase CO2-bearing and two-phase aqueous inclusions. The fluid inclusions demonstrate the modes of homogenization temperatures of 363.3℃, 325.5℃, 273℃, 258.62℃ and salinities of 14.53, 9.59, 11.61, 8.03 wt% NaCl.equiv., for stages II, III, IV, and V respectively. The ore-forming fluid in the Fancha deposit belonged to the CO2-H2O-NaCl-(±CH4) fluid system with mid-low temperature and mid-low salinity. The δ18OH2O of the metallogenic fluids was between 1.36 and 6.28, and the δDH2O was between -87 and -53.1. Hydrogen and oxygen isotope data indicate that the ore-forming fluids were dominated by metamorphic fluids in the early stage, and that the metamorphic fluid gradually mixed with circulating meteoric water during the later stages. Petrographic observation and microthermometry suggest that fluid mixing and immiscibility obviously occurred during the main metallogenic stage. Fluid mixing and fluid immiscibility probably led to gold deposition in the Fancha deposit.

Trace Element Geochemistry in Quartz in the Jinqingding Gold Deposit, Jiaodong Peninsula, China: Implications for the Gold Precipitation Mechanism

Lots of studies on gold precipitation mechanisms have focused on fluid inclusions within quartz. However, the trace elements in quartz reflect the properties of the ore fluid, and a comparison of the trace element content in different types of quartz can reveal the precipitation mechanism. The Jinqingding gold deposit is the largest gold deposit in the Muping–Rushan gold belt and contains the largest single sulfide–quartz vein type orebody in the gold belt. This study distinguished four types of quartz in this orebody through field work and investigations of the mineralogy and cathodoluminescence (CL) of the quartz and crosscutting relationships as seen under a microscope. In situ studies via electron probe micro-analyzer (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were used to determine the trace element content of the different quartz types. Type Qa displayed a comb structure in the field and zoning under the microscope and in CL. Milky white and smoke grey Qb was the most common quartz type and hosted the most sulfide and gold. Qc was Qa and Qb quartz that recrystallized around pyrite or overgrew and appeared different from Qa and Qb in CL images. Qd occurred within fractures in pyrite. Qa formed prior to the mineralization of gold, and Qd formed post-mineralization. Qb and Qc provided information regarding the ore fluid during mineralization. Sericites occurred with pyrite in fractures in the quartz, and some, along with free gold, filled in fractures in pyrite. Free gold occurred within Qa, Qb, Qc, and in brittle fractures in pyrite. Qc had the lowest Al content of all of the quartz types. As Al content is related to the acidity of the ore fluid in previous study, this indicated an acidity decrease during mineralization, which could be attributed to the sericitization. Sericitization could indicate a potential gold occurrence. The Ti content decreased from Qb to Qc, indicating a decrease in temperature during quartz overgrowth formation. Change in acidity and cooling can therefore be identified as possible causes of gold precipitation in the sulfide–quartz vein type in the Jinqingding gold deposit.

Multicore large-aperture fiber-optic probe based on quartz–quartz-type lightguides for near-infrared fluorimeters

The optimization problem of the parameters of lightguides for fiber-optic probes used in fluorescent tumor diagnostics (of benign and malignant tumors) is considered. It has been shown that, to increase the sensitivity of a fluorimeter in the near-infrared region, it is promising to use fiber lightguides of the quartz–quartz type, with an increased numerical aperture of up to 0.30 and a biocompatible protective coating of P-12 polyamide or tetrafluoroethylene copolymer with Tefzel ethylene, as probe lightguides for detecting luminescence. Using such lightguides, a prototype version of a 19-core large-aperture fiber-optic probe for a laser oncofluorometer with increased sensitivity operating in the spectral range 900–1100 nm has been developed. The minimum dose of the injected drug was 10 μg/kg of bio-object weight, which corresponds to a world-class level of sensitivity of photosensitizer detection in biological tissues.

Synthesis of Nanosilica from Padas Stone to Reduce The Total Organic Carbon of Palm Oil Waste

Padas stone is one of the natural mineral containing 67.5% of SiO2 compounds. In this research, synthesis of nanosilica was carried out by sol-gel method asistanced by 2.45 GHz microwave radiations with low (10%), medium (50%) and high (100%) power at 30 and 60 minutes of contact times. It was analyzed by XRD, BET, FTIR spectrophotometry and SEM. The synthesized silica was then used as absorbent for total organic carbon (TOC) of palm oil waste. The results show that the synthesized silica was a mixture of cristobalite and quartz type minerals according to ICDD No. 00-003-0271 and 01-083-287. The surface area and silicon dioxide contains are 12.174 m2/g and 76.325% for silica without microwave assistance (SiO2-TPMW); 12.796 m2/gand 86.385% for silica with 30 minutes on 10% microwave assistance(SiO2 -MW 10A); 12.735 m2/gand 86.254% for silica with 60 minutes on 10% microwave assistance (MW 10B); 13,659 m2/gand 87.211% for MW 50A; 13,583 m2/g and 86.684% for MW 50B;7.883 m2/gand 57.527% for MW 100A; also 8.752 m2/g and 37.725% for MW 100B, respectively. The use of silica as an absorbent of TOC shows the effectiveness of 62.89% (TPMW); 63.68% (MW 10A); 62.96% (MW 10B); 65.25% (MW 50A); 64.61% (MW 50B); 62.37% (MW 100A) and 61.18% (MW 100B) from the initial TOC of 1520 mg/L. Keywords: synthesis, nanosilica, padas stone, total organic carbon, oil waste.

Experimental study of sand grains behavior at their contacts with force- and displacement-controlled sliding tests

Discrete element modeling requires the proper quantification of the behavior of grains at their contacts including the normal force – displacement and tangential force – displacement relationships to be used as input for contact modeling purposes. This paper reports on recent advances in soil mechanics experimentation which allowed measuring the grain contact behavior of small sand particles quantifying friction and stiffness with sliding tests of a force-controlled or displacement-controlled type. The particular focus of this work is on the micromechanical behavior of quartz type grains of size between about 1 and 5mm. A description of the developed micromechanical apparatus at City University of Hong Kong is first discussed and its important different capabilities with previously developed apparatus is briefly reviewed. Subsequently, a limited set of new data is reported and discussed along with a review of recently acquired results published in the literature associated with the contact behavior of quartz sand grains. These sliding tests have covered a wider range of normal contact forces from about 0.5 to 8N, and the results indicated that, for this range of confining forces, there is not any notable change of the inter-particle coefficient of friction.

Depositional environment and origin of the Lilaozhuang Neoarchean BIF-hosted iron–magnesite deposit on the southern margin of the North China Craton

The Neoarchean Lilaozhuang iron–magnesite deposit is located in the middle of the Huoqiu banded iron formation (BIF) ore belt in Anhui Province on the southern margin of the North China Craton. The Huoqiu BIF is the unique one that simultaneously develops quartz-type, silicate-type, and carbonate-type magnetite in the region. The Lilaozhuang deposit is characterized by magnesium-rich carbonate (magnesite) in magnetite ores. The BIF-hosted iron ores include mainly of silicate type and carbonate type, with a small amount of quartz type, which chiefly exhibit banded and massive structure, with minor disseminated structure. The magnesite ores occur as crystal-like bright white and exhibits massive structure. The Y/Ho ratio and REY pattern of both iron and magnesite ores are similar to that of seawater, while Eu shows positive anomaly, which is the sign of seafloor hydrothermal mixture. These features suggest that ore-forming materials of iron and magnesium in the Lilaozhuang deposit are mainly from the mixture of seafloor hydrothermal and seawater. Both ores do not exhibit negative Ce anomaly, which indicates that the deposit was formed in an environment showing a lack of oxygen. C–O isotopic compositions indicate that magnesite ore has been reformed by metamorphism of low amphibolite facies and later hydrothermal alteration. Based on the comprehensive analysis, authors suggest that iron and magnesite ores in the Lilaozhuang deposits formed in a confined sea basin on continental margin and was influenced by later complex geological processes.

Microscopical and mechanical evaluation of the durability of SiO2aggregates

The durability of SiO 2 compounds is closely related to its structural properties. In this work three natural siliceous aggregates (called G1, G2 and G3) are studied. Improvement of the durability of the starting material leads to a significant energy savings by extending the lifetime of structures. The chemical composition of the three natural aggregates shows that G1 and G2 have almost the same chemical composition (SiO 2 ) and G3 is different and contains SiO 2 quartz type and calcite as major components (SiO 2 , calcite and dolomite). X-ray diffraction (XRD) shows that natural aggregates G1 is more crystallized than G2 and G3. After alkali silica reaction (ASR) process, the reactivity of G3 aggregate seems to be higher than the G1 and G2 aggregates. The mechanical results show the slight difference between mortar containing G1 (M_G1) and that containing G2 (M_G2). Their compressive strength is 10% less than that of reference (M_SS). As it is more reactive, G3 seems improving the compressive strength of M_G3, compared to M_G1 and M_G2.

Kysylga gold–silver deposit in the terrigenous sequences of the Verkhoyansk–Kolyma mesozoides

The paper reports the mineralogical and geochemical features of the Kysylga gold deposit located in the hornfelsed Norian sedimentary rocks and classified with low-sulfide gold–quartz type of deposits typical of the Verkhoyansk–Kolyma metallogenic province. Detailed typomorphic study of the major minerals (quartz, arsenopyrite, and gold) of the ore veins shows that the deposit is assigned to the gold–silver type. Mineralogical and geochemical data substantiate this conclusion.

Transmission photocathodes based on stainless steel mesh and quartz glass coated with N-doped DLC thin films prepared by reactive magnetron sputtering

The influence was investigated of N-doped diamond-like carbon (DLC) films properties on the quantum efficiency of a prepared transmission photocathode. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh and quartz glass (coated with 5 nm thick Cr adhesion film) by reactive magnetron sputtering using a carbon target and gas mixture Ar, 90%N2+10%H2. The elements' concentration in the films was determined by RBS and ERD. The quantum efficiency was calculated from the measured laser energy and the measured cathode charge. For the study of the vectorial photoelectric effect, the quartz type photocathode was irradiated by intensive laser pulses to form pin-holes in the DLC film. The quantum efficiency (QE), calculated at a laser energy of 0.4 mJ, rose as the nitrogen concentration in the DLC films was increased and rose dramatically after the micron-size perforation in the quartz type photocathodes.