Abstract:The late Paleozoic granitic rocks are widely exposed in Dornogovi Province of Southern Mongolia, which is located in the core of the Central Asian orogenic belt. Accurate isotopic dating and petrogenetic studies of the granitic rocks are of great scientific significance for the in-depth understanding of the crustal evolution characteristics of the Central Asian orogenic belt. In this study, two Early Carboniferous granites (337 Ma and 332 Ma) and two Late Carboniferous granites (320 Ma and 306 Ma) were identified in Zamyn-Uud and Ulan Badrach. To be specific, the content of SiO₂ (76.31% to 77.79%) is relatively consistent with that of K₂O+Na₂O (8.23% to 8.59%) in the Early Carboniferous granites, while the variation range of the content of SiO₂ (72.65% to 76.22%) and K₂O+Na₂O (7.89% to 8.67%) in Late Carboniferous granites is higher than that in Early Carboniferous granites. Both Early and Late Carboniferous epochs are characterized by weakly peraluminous I-type granites, of which elements such as U, Th, K, Zr and Hf exhibit positive anomalies, and elements such as Sr and Ti exhibit negative anomalies. Based on an isotopic analysis of whole-rock Sr-Nd and zircon Lu-Hf, the authors detected that the Early Carboniferous granites have positive εNd(t) (+3.68~ +4.09) and εHf(t) (+9.70~ +14.90) values in comparison with young two-stage model age of Nd (t_DM2=792~753 Ma) and the two-stage model age of Hf isotopes (t_DM^c =721~393 Ma). The above evidence indicates that the Early Carboniferous granites were partially melted from juvenile basaltic oceanic crust, under the influence of mantle-crust interaction, showing the crust accretion of the Early Carboniferous. Unlike the Early Carboniferous, the granites in Late Carboniferous have higher εNd(t) (+1.17~+5.31) and εHf(t) (+13.68~ +15.21), Nd model age (t_DM2=984~636 Ma) and the two-stage model age of Hf isotopes (t_DM^c =442~344 Ma), demonstrating that the material source was mainly composed of juvenile crustal materials and a small quantity of ancient crustal materials. Based on the existing results, the authors believe that the tectonic background of the Carboniferous granites recorded the transformation of the regional extensional environment caused by slab roll-back of oceanic plates during the late Carboniferous to the post-collision extensional environment in the later period.

Abstract:Zircon U-Pb dating and geochemical characteristics of Late Devonian Baogede granite in the southern part of the Xing'an block were studied and its petrogenesis and geological significance were discussed in this paper. The rocks are composed of quartz monzonite, monzonitic granite and granite porphyry. Zircon U-Pb dating results of syenogranite and alkali-feldspar granite are 368±1 Ma, 364±1 Ma and 355±1 Ma respectively. indicating that they are the products of magmatic activity in the Late Devonian to Early Carboniferous period. (Na₂O+K₂O)=7.62%~8.82%, K₂O/Na₂O=0.93~4.21, characterized by full high alkali content and high potassium. A/CNK=0.95~1.20, suggesting metaluminous to weakly peraluminous rocks. They belong to the high-K calc-alkaline series I-type granites. They are low in total REE (83.60×10^-6~163.40×10^-6), and the negative europium anomaly is medium (δEu=0.34~0.78). They are rich in large ion lithophile elements (Rb, Th, K) and light rare earth elements, and have suffered from different degrees of loss of Ba, Sr, P and Ti elements. The Baogede granite was formed in an extended environment of the active continental margin, and ts formation was related to the Paleo-Asian Ocean.

Abstract:Radioelement content, rock density and rock thermal conductivity of drill hole samples within Douzhashan pluton of northern Guangxi were analyzed. The results suggest that the average U, Th and K₂O values of the investigated granites are 17.49×10^-6, 27.54×10^-6 and 4.64%, respectively. The average value of rock density is 2.57 g/cm³, which is in good agreement with the average density of granites in the world. The average radiogenic heat production of the investigated granites is 6.46 μW/m³, which is obviously higher than that of crustal rock and most plutons in South China. The main heat production contribution is sourced from the decay of U and Th, and the U plays the most important role. The average rock thermal conductivity is 3.389 W/mK, close to that of the middle-upper crustal rocks. Combined with the previous data around the study area from previous researchers, this paper indicates that the crust contributes more heat flow to the surface than the mantle, thus the area of Miao'ershan and northern Guangxi is a typical region with cold crust and hot mantle type lithospheric thermal regime. Based on the advantages of radioelement content and radiogenic heat production, the authors hold that the Douzhashan pluton has a great exploration potential as hot dry rock resource, and hence more further work is needed in the future.

Abstract:Based on the relationship between uranium minerals and pyrite from different types of uranium ores in the Mianhuakeng deposit, the authors investigated the mechanism for the deposition and enrichment of uranium during the ore-forming process. The research shows that uranium orebodies in the Mianhuakeng deposit generally occur in vein-filling or vein-disseminated form. Uranium ore types include fluorite type, carbonate type, siliceous vein type and reddening type. Although different ore types have different gangue minerals formed in the mineralization period, they show common characteristics as follows: Uranium minerals in the central part or along the vein walls are alternatively arranged with gangue minerals or occur in veinlike or disseminated form in cataclastic altered granite and are inlaid with gangue minerals such as calcite, fluorite and microcrystalline quartz. Uranium minerals and pyrite are closely associated with each other in aggregate or relatively independent states, and the boundaries between them and gangue minerals in the mineralization period are straight, with good crystal type and in inlaid growth form. The aforementioned evidence indicates that there is no sequential generative relationship between pyrite and uranium minerals, and that they are all co-crystalline products of ore-forming fluid. Uranium precipitation had nothing to do with redox reaction. In contrast, decrease of pressure and temperature and the change of pH and solubility were the main factors that triggered the precipitation of uranium and gangue minerals.

Abstract:The Mboukoumassi region of Congo has tropical rain forest climate, possesses important Cretaceous potash deposits at the western edge of the African continent, and hence belongs to the typical rift potassium basin. Mineralogical studies show that the main types of evaporite minerals are chloride minerals comprising halite, carnallite, kalitite, brucite and spillite, sulfate minerals comprising gypsum, anhydrite and some other minerals. The sequence of evaporite mineral deposition is in order of gypsum, anhydrite (most cycles are missing) → stone salt → carnallite → potassium salt (secondary) → spillstone or magnesite. According to the characteristics of evaporite mineral deposition and the analysis of trace elements, it is shown that, in the Cretaceous period, the Mboukoumassi area was in a long-term high temperature and dry environment, which was conducive to the evaporation and concentration of brine and the formation of salt mineral deposition.

Abstract:A new magnetite reference material, named CAGS-MAG, was prepared by the Institute of Geology, Chinese Academy of Geological Sciences. One-way analysis of variance was used to test the homogeneity of CAGS-MAG, and trend analysis was used to test the stability of CAGS-MAG during 30 months (five times). CAGS-MAG showed sufficient homogeneity and stability for use as a Fe isotope reference material. The property value was determined by an interlaboratory comparison of results from five participating laboratories, which were Institute of Geology, Chinese Academy of Geological Sciences, University of Science and Technology of China, China University of Geosciences (Beijing), Tianjin University, and Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The property value was calculated from the unweighted means of the results submitted by the participating laboratories. Uncertainties were associated with batch characterization (u_char), possibility between-bottle variations (u_bb'), and those derived from effects related to long-term storage (u_lts). The property values[δ⁵⁶Fe_IRMM-014(‰) and δ⁵⁷Fe_IRMM-014(‰)] for CAGS-MAG are 0.68 and 0.99, with a combined expanded uncertainty (k=2) of 0.10 and 0.13 respectively. CAGS-MAG can be used to validate chromatographic separation and total measurement procedures and to conduct inter-laboratory comparisons when Fe isotopes of iron ore samples, such as hematite samples and magnetite samples, were measured.

Abstract:Taking vanadium-titanium magnetite electric furnace slag as the research object, the authors systematically studied chemical composition, mineral composition, mineral and element distribution characteristics of the slag by means of chemical analysis,X-ray diffraction analysis and electron microprobe analysis. The results show that 94.74% Ti exists in anosovite, Mg and Al mainly occur in the form of magnesia alumina spinel, calcium and silicon are mainly in the form of diopside, while iron is dispersed in various minerals. The valuable mineral is anosovite, which is mainly disseminated with diopside, and partly distributed in spinel. Besides, some of Mg and Al occur in anosovite in the form of isomorphous admixture; as a result, the content of TiO₂ in anosovite is only 82.04%. The result can provide scientific basis for the comprehensive utilization of vanadium-titanium magnetite electric furnace slag.

Abstract:Oxygen fugacity is a parameter that reflects the oxidation state of the mantle, and it is controlled by temperature, pressure, chemical composition of rock, mineral structure and some other factors. The studies of the oxygen fugacity of the upper mantle are mainly focused on the aspects of the magnesium-olivine- magnetite-quartz system, amphibole-bearing peridotite, basalt (melt) and experimental petrology method. It is widely accepted that mantle oxygen fugacity decreases with the increase of the depth. Nevertheless, natural samples and theoretical studies suggest that the oxygen fugacity of asthenosphere is higher than that of the overlying lithosphere mantle, and even that such an inverse gradient may exist for mantle transition zone compared with the upper mantle. The differences between different tectonic environments and different regions with similar tectonic environments indicate the heterogeneity of oxygen fugacity in horizontal direction. The relationship between substances flux of different layers and the variance of oxygen fugacity is one of the focus in future research on oxygen fugacity. The subduction zone is a great natural laboratory for exploration. Meanwhile, oxygen fugacity in turn influences species of volatiles and their circulating fluxes in different reservoirs, such as carbon and sulfur.

Abstract:In this paper, the natural zeolites from Weichang area were treated with sodium hydroxide. X-ray diffractometer, infrared spectrometer, N₂ adsorption-desorption technique and scanning electron microscope were employed to characterize the materials, water vapor adsorption method was adopted to evaluate the hydrophilicity of materials, and Cr and Mn ions were used to determine the ion exchange property of materials. The effect and the mechanism of alkali treatment on structure, hydrophilicity and ion exchange property of natural zeolites were then investigated. The results show that the natural zeolites from Weichang area contain clinoptilolite, quartz and illite. Alkali treatment could decrease the SiO₂/Al₂O₃ ratio of natural zeolites, and the SiO₂/Al₂O₃ ratio gradually decreases with the increase of alkali concentration. The influence of alkali treatment on structure of clinoptilolite is higher than that of quartz and illite. The structure of natural zeolite is destroyed, the specific surface area of natural zeolite decreases and the pore volume of natural zeolite increases under high alkali concentration. The hydrophilicity and ion exchange property of natural zeolites gradually increase, accompanied by the decrease of SiO₂/Al₂O₃ ratio.

Abstract:The Qinghai Lake is the only modern inland saltwater lake in China where dolomite, calcite and aragonite are reported to coexist in lake bottom sediments. To discuss the influence of magnesium on the polymorphs of calcium carbonate, the authors chose Qinghai Lake water and sterilized Qinghai Lake water as the reaction solution and CaCl₂ and MgCl₂·6 H₂O as the reactants, and precipitated calcium sulfate and calcium carbonate by the method of variable-controlling with different concentrations of Mg²⁺ at laboratory room temperature. When only CaCl₂ was added into Qinghai Lake water, gypsum (CaSO₄·2 H₂O) and vaterite (CaCO₃) were precipitated. However, when CaCl₂ and MgCl₂·6 H₂O were added together into the lake water, gypsum disappeared, and the synthetic products changed to calcium carbonate, including calcite and vaterite. When Mg²⁺ concentration in lake water water increased to 0.62 mol/L, vaterite disappeared, and the products were composed of calcite and aragonite. With the increasing of Mg²⁺ concentration, the content of aragonite rose steadily, while content of calcite decreased gradually. When Mg²⁺ concentration rose to 1.22 mol/L or higher, calcite disappeared completely, only aragonite was precipitated from the solution. These results indicate that the SO₄^2- in lake water inhibited the formation of CaCO₃ under the condition of no or very low concentration of Mg²⁺. However, when extra Mg²⁺ added into the lake water, they could release the inhibition of SO₄^2-, and then Ca²⁺ were free to combine with HCO₃^- and CO₃^2- to form calcium carbonate. In addition, the polymorphs of synthetic calcium carbonate was obviously controlled by Mg²⁺ concentration. With the increase of Mg²⁺ concentration in the lake water, calcite and vaterite were no longer stable, while aragonite was gradually dominant. When Mg/Ca reached 6.1, only aragonite was stable in the reaction product.

Abstract:Gem-quality garnets in Jinan of Shandong Province occur on the northern margin of the middle basic rock mass in the urban area. Because of badly ruined profiles and lack of gemological reference, gemological instrument, FTIR, EPMA and UV-VIS were used to investigate the characteristics of Jinan garnets. Jinan garnet's host rocks can be divided into early-formed skarn and late-formed pegmatite. Skarn garnet crystals are subhedral to unhedral in form, and their main component is andradite with minor grossular, mainly black-palm red or orange red and minor green in color. The pegmatite garnet's crystals are mainly of euhedral rhombic dodecahedron shape, mainly in green or yellow color, and the component is mainly grossular with minor andradite. Inclusions of pegmatite garnets are mainly needle-like actinolite and feldspar crystal inclusions. Jinan garnet crystals can show obvious bands of black-reddish brown-yellow-yellowish green-green color from the early epoch to the late. Green garnets have the characteristics of abnormal extinction, uneven Cr content, high Fe-Ti-Cr content in dark green rims and low content of Y. Black garnets have high Ti content and contain black spinel inclusions. The spinel and actinolite inclusions in Jinan garnets are different from gem-quality garnets of other regions.

Abstract:Microscope, LA-ICP-MS, (Micro)FT-IR, UV-Vis, Raman and other methods were used to analyze conventional gemology, chemical element content and spectral features of Pakistan peridot, so as to discuss its origin characteristics. The result shows that Pakistan peridots contain black Vonsenite-Ludwigite needle and punctiform msgnetite. Compared with peridots from the USA, China, Ethiopia, Vietnam and Madagascar, Pakistan perdots have higher Li, B, Sc but lower Zn, Cu, with relatively lower V/Sc ratio. The absorption bond around 3 580 cm^-1 in the infrared absorption spectrum of peridot in Pakistan is related to the [Si]=(4H)_Si^X substitution mechanism, indicating that the crystal structure contains a certain amount of structural water. The strong absorption near 380, 450, 490, 635 nm in UV-Vis spectrum is related to O^2-→Fe³⁺ transition, ⁶A₁→⁴A₁+⁴E(⁴G)in d-d transition of Fe³⁺ and ⁵T_2g→³T₂, ⁵T_2g→³T_1g electron transition of Fe²⁺. It is concluded that inclusion, trace element and structural water-induced infrared absorption band can be used as the origin identification characteristics of peridots in Pakistan.

Abstract:The widespread use of rare earth elements has attracted increasing attention. Studies have shown that rare earth elements play an important role in such aspects of the crop as photosynthesis, yield, stress resistance, quality, development and nutrient absorption of crops. Therefore, effective decomposition and rapid determination of rare earth elements in soil can reasonably guide the application of rare earth elements and play an important role in crop growth and soil nutrition. Methods of digestion such as acid digestion, closed acid digestion, microwave acid digestion and alkali melting were studied in this experiment. Microwave digestion-ICP-MS method was adopted which can rapidly and effectively determine rare earth elements in soil. The experiment optimized the digestion conditions including microwave digestion program, dosage of chemical reagent, digestion temperature, and digestion time. The detection limit, precision, accuracy and recovery were tested, which shows the method is effective and feasible. The value was 0.16%～3.39%, 0.27%～5.09% and 93.1%～106.0%.

Abstract:The paper is a systematic collection of 112 new minerals approved by the Commission on New Minerals,Nomenclature and Classification (CNMNC) of the International Mineralogical Association(IMA) in 2014, by listing mineral name, crystallochemical formula, crystal structure data, physical and optical properties, locality of origin and occurrence, relationship with other minerals, source of mineral names, chemical reaction and spectroscopic characteristics. It's very meaningful that Chinese names of 112 new minerals have been examined and revised under the authority of Chinese Commission of New Minerals and Mineral Names. As a part of the comprehensive introduction to discovery and research of new minerals in the world, this paper will provide reference for the work of discovering, researching and naming new minerals in China and promote the standardization of Chinese names of mineral species.