Abstract:This paper reports LA-ICP-MS zircon U-Pb dating data as well as whole rock major and trace element data from granite pluton in the Yaodonggou area of the North Qilian orogenic belt. The result shows that the pluton was emplaced at 466±2 Ma. The Yaodonggou granite contains high SiO₂ (72.45%~80.18%) and Alk (6.04%~8.12%). Its K₂O content is less than that of Na₂O with K₂O/Na₂O ratio of 0.07~0.71, Ritterman index of 0.96~2.16 (less than 3.3), and A/CNK of 0.94~1.01. The granite belongs to low-medial potassium calcium alkaline series quasi-aluminum rocks. The chondrite-normalized REE patterns show the right-inclined type of LREE enrichment, with a medium negative Eu anomaly and δEu of 0.67~0.81. The primitive mantle-normalized spidergram shows depletion of Nb, Ta, Ti, P and enrichment of Rb, K, U. The P₂O₅-SiO₂ diagram shows the trend of I- type granite. The Y-Rb diagram shows the characteristics of differentiated I-type granite. Combined with the regional geological background, the authors hold that the formation of the Yaodonggou granite was probably related to the northward subduction of the North Qilian Ocean Basin, which led to the back-arc extension and mantle-derived magmatic intrusion and uplift. As a result, the ancient crustal material was remelted to form parent magma, then it was subjected to moderate crystallization differentiation. The magma had the property of island arc magma, which might have been attributed to the fact that the back arc basin was split on the basis of island arc or its magma source area was reformed by subduction plate fluid or melt.

Abstract:The Yuanbaoshan Late Carboniferous granite is located in the Yuanbaoshan area, Ejin Banner, Inner Mongolia. Its rock mass characteristics are of great significance for the study of the properties of the Hongshishan ophiolite belt and the reconstruction of the tectonic evolution of the northern Beishan region. LA-ICP-MS zircon U-Pb isotopic dating shows that the ages of granodiorite, monzonitic granite, and trondhjemite in the Yuanbaoshan composite batholith are 317.1+3.1 Ma, 314.8+2.7 Ma and 313.7+2.3 Ma respectively, suggesting Late Carboniferous. The petrogeochemical analysis shows that the granites of the Yuanbaoshan composite batholith have high silicon (SiO₂=67.77%~73.00%), and rich sodium (K₂O/Na₂O<1) with A/CNK being 0.95~1.13, belonging to partially aluminous to weakly peraluminous,with the enrichment of LILEs (Rb, Ba, Th, K), depletion of HFSEs (Ta, Nb, P, Ti) and medium strength negative europium anomaly (δEu=0.46～0.65), similar to the petrogeochemical characteristics of island arc environment. The trondhjemite is different from the granodiorite and monozonitic granite; it is rich in silicon, has very weak negative europium anomaly (δEu=0.81~0.99), high Sr/ Y and La/Yb ratios, and falls into the adakite area on the Sr/Y-Y diagram. These differences suggest that they have different source characteristics. According to the regional geological data, the subduction of the Hongshishan oceanic plate under the study area during the early Late Carboniferous initiated large-scale magmatic activity and formed the Yuanbaoshan granite composite batholith with island arc affinity. The plagioclase granite with adakite-like characteristics originated from partial melting of the subductional oceanic plate, implying that the Hongshishan Ocean might have had a relatively young hot oceanic crust during the early Late Carboniferous period.

Abstract:Amphibole and biotite are dark-colored minerals commonly found in highly differentiated alkaline granite containing REE-bearing and rare metal-bearing minerals. The different compatibilities of amphibole and biotite for different elements (especially rare metals and rare earth metals such as Nb, Ta, Zr and REE) make their characteristics of major and trace elements become the "log" of magma evolution, which has a significance in the reconstruction of the petrogenesis and mineralization process of ore-bearing magma. In order to determine the enrichment and distribution process of elements such as Nb and Ta during the magmatic crystallization, the authors studied mineral chemistry of amphibole and biotite in the Boziguo'er alkaline granite pluton in Baicheng, Xinjiang, by means of electron microprobe (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The amphibole in the pluton is arfvedsonite, which is generally characterized by high Na and Fe and relatively poor Ca (<0.15 apfu), Mg (<0.06 apfu) and Ti (<0.07 apfu). The uniformity of the composition and the deficit of LREE suggest that the amphibole was crystallized at the late stage and a large number of LREE-rich minerals were crystallized before amphibole. According to the association relationship, the biotite is divided into two types(type-A and type-B)in this paper, which have different chemical compositions. Compared with type-B, type-A has a higher content of F (3.81%~4.82% in type-A and 1.68%~3.65% in type-B) and SiO₂ (41.5%~43.3% in type-A and 35.9%~38.5% in type-B), and a lower content of TFeO (28.0%~31.4% in type-A and 32.2%~35.7% in type-B) and Al₂O₃ (6.45%~7.62% in type-A and 9.70%~11.00% in type-B). The different values of fluorine in biotite and amphibole indicate the enrichment and saturation process of fluorine in the crystallization process and a large number of REE-bearing and rare metal-bearing minerals crystallized on account of fluorine saturation. Due to the incompatibility in the main minerals, the ore-forming elements Nb and Ta should be gradually enriched in the melt, whereas the Nb/Ta ratios of the main minerals and most of the secondary minerals are higher than those of the bulk-rock, resulting in "Ta-missing". Combined with previous studies, it is believed that the combination of the volatile saturation and the crystallization of zircon caused the separation of Ta from the melt.

Abstract:The Shapinggou molybdenum deposit is the second largest porphyry molybdenum deposit in the world. The mafic-ultramafic rock widely exposed in the area of Shapinggou molybdenum ore deposit is an important medium to reveal the deep information of the deposit. In this paper, the olivine-bearing amphibolite outcropped in the mining area were studied based on petrology, petrography and in situ analysis so as to clarify physicochemical conditions of diagenesis and discuss the petrogenesis and tectonic setting. The main rock-forming minerals contain olivine, amphibole, phlogopite and pyroxene, and the accessory minerals are apatite, chromium-iron spinel, mafic spinel, magnetite, pyrrhotite and pentlandite. The results of in-situ analysis of EPMA show that olivine belongs to the chrysolite series, amphibole is parasite, pyroxene is diopside and mica is phlogopite. The order of crystallization is olivine-pyroxene-amphibole, the temperature ranges from 1 111.64 to 1 223.30℃ and the formation pressure ranges from 350 to 740 MPa, with high oxygen fugacity (the oxygen fugacity varies from NNO+0.59 to NNO+2.27). The mineralogical characteristics of phlogopite and amphibole indicate that phlogopite was related to mantle-derived magmatism. The study shows that the parent magma of olivine-bearing amphibolite originated from the mantle and was formed through crystallization differentiation of basalt magma which was partially melted by 7.92% of the mantle. The olivine-bearing amphibolite outcropped in the north of Shapinggou mining area should be the product of partial melting of mantle-derived magma under the extensional tectonic background.

Abstract:Biotite is an important rock-forming mineral in most of granites, and its mineral chemistry can reveal the crystallization conditions, petrogenesis and tectonic setting in the magma system. In this study, the authors utilized electron microprobe analysis (EMPA) to determine the mineral composition of biotite grains hosted in the Pailou granite. The EMPA data show that the biotite is poor in Al^Ⅵ (0.128 to 0.395) atomic number and moderate in Ti (0.236 to 0.267) atomic number, and shows siderophyllite affinity. In addition, the biotite is rich in iron and poor in magnesium, with Fe²⁺/(Fe²⁺+Mg) values from 0.985 to 0.989. Petrography and mineral chemistry indicate that the biotite grains are of magmatic origin. Based on calculation of the EMPA data, the crystallization temperature and pressure of biotite are 640～710℃ and 0.9～1.7 GPa, respectively. Besides, it was formed under the condition of low oxygen fugacity, with the log f_O2 values from -18.1 to -17.4. The low oxygen fugacity of magmas can explain the lack of Cu, Au and Mo mineralization, whereas the lack of Sn mineralization may be attributed to the low temperature of magmas. Combined with the study of mineral chemistry of biotite and geochemical features of hosted rocks, the authors hold that the Pailou monzogranite is of A-type and was formed in the nonorogenic tectonic setting.

Abstract:Ningwu Basin, which is characterized by widespread porphyritic iron ore deposits, is one of the seven ore concentration areas in the Middle and Lower Yangtze metallogenic belt. The Washan iron deposit, which is one of the important representatives of porphyric iron-ore deposits in Ningwu Basin, is located in the middle of the basin. In this study, the result of Re-Os isotopic dating of pyrites collected from the Washan iron deposit was reported. It is for the first time that the metallogenic age was determined by iron-bearing metallic minerals in Ningwu area. The results show that the Re-Os isochron age of pyrites in Washan iron deposit is 127.7±2.6 Ma(n=5,MSWD=0.66), which can directly represent the metallogenic age of the Washan iron deposit. The initial ¹⁸⁷Os/ ¹⁸⁸Os ratio is 1.73±0.56,and the γ_Os(t) values are from 527.18 to 535.93, which are between the value of the mantle and that of the crust. Combined with previous studies, it is suggested that ore-forming materials of the Washan iron deposit was mainly derived from the enriched mantle and partly from the crust.

Abstract:The values of Fe, Cd, Mn and other trace elements in sphalerite not only influence its cell parameters but also contain rich information concerning the genesis of the ore. There are two types of ore in the Dingjiashan Pb-Zn ore district of the Meixian orefield in central Fujian Province: the magnetite-type and the pyrrhotite-type. In this paper, the cell parameters and values of Zn, Fe, Cd and Mn of sphalerite in two types of ore were tested by X-ray in situ and electron microprobe analysis. In terms of the cell parameters of sphalerite, the characteristics of pyrrhotite-type > magnetite-type > the theoretical value are mainly caused by different values of Fe and Mn in sphalerite. In addition, the gap of Fe average values in sphalerite in two types of ore is much larger, and the substitutional relation and intensity between Zn, Fe and Cd of sphalerite in two types of ore are completely different. Combined with the geological characteristics of the study area, the authors consider that these two types of ore may be products of two kinds of mineralization.

Abstract:A large number of primary melt inclusions and crystal-rich fluid inclusions are developed in two-mica granites and pegmatites in Jiajika deposit, western Sichuan. In this study, the authors identified the mineral types of glass from melt inclusions of quartz in two-mica granite and daughter minerals from fluid inclusions of beryl and spodumene in pegmatites by means of laser Raman and scanning electron microscopy. According to the experimental results, Jiajika glass from melt inclusions of quartz in two-mica granite consists mainly of apatite+muscovite, muscovite+albite and muscovite+graphite. Crystals from fluid inclusions of beryl comprise mainly corundum, alumina-rich ferrosilicate+corundum+spodumene, spodumene+quartz+lithium chlorite. Crystals from fluid inclusions of spodumene are composed mainly of apatite, cassiterite, magnetite, quartz+albite+lithium chlorite, fluorite, calcium-magnesium-rich silicate+alumina-rich ferrosilicate+ferrosilicate+quartz. From early granite to pegmatite, the melts and fluids in the metallogenic melt and fluid in general showed high values of Na, Si, Al and F, and decrease of Fe, Mg and Ca. The ore-forming fluid of early granitic pegmatite magma to beryl and spodumene subminerals showed inheritance and some differences, with the existence of local pegmatite magma, magma immiscibility and non-uniformity. The increase of volatilization content of F, P and CO₂ in pegmatite played an important role in the mineralization of rare metals.

Abstract:A method for determination of trace silver in stream sediments, soils and rocks by graphite furnace atomic absorption spectrometry (HNO₃-H₂O₂) was developed in this study. The microwave digestion and instrument working parameters were optimized and the optimum conditions were determined. In traditional method, determination of trace silver in geochemical exploration samples is conducted by graphite furnace atomic absorption spectrometry through heating the hydrochloric acid nitric acid hydrofluoric acid and perchloric acid electric heating plate digestion, with iridium, platinum as matrix modifier; the analytical process is complex, and the cost is high. Compared with the electric heating plate digestion method, the microwave digestion technique is characterized by high-pressure closed digestion with small amounts of acid, complete digestion and less loss in the digestion process. In this paper, HNO₃ (65%) and H₂O₂ microwave digestion was used to dissolve the matrix interference by adding 12 g/L thiourea as the medium. The detection limit was 0.018 μg/g, and the analytical method was used for verification of sediment reference materials (GBW07309, GBW07311), soil standard substance (GBW07402, GBW07404) and rock reference materials (GBW07103, GBW07104). The measured results were consistent with the recommended values, the accuracy of lgC (GBW) is △lgC(GBW)≤±0.024, RE(GBW)≤±5.71%, the precision of RSD (GBW) is ≤5.97%. The method is suitable for the determination of trace silver in a large amount of geochemical samples.

Abstract:Safe disposals of high level radioactive-waste have become a serious problem for the sustainable and healthy development of the nuclear industry. Nuclear waste forms based on crystalline mineral phases have attracted great attention, because of their excellent performance. Among them, titanite or sphene (CaTiSiO₅) is proposed as a host phase for the immobilization of radioactive nuclides, especially high level of nuclear wastes, because of its good anti-radiation properties. Due to radioactive decay of radionuclides, especially α-decay, the crystal structure of titanite may be damaged and in the metamict, an aperiodic or amorphous state. In order to evaluate the physical and chemical properties and long-term stability of titanite solidification, it is necessary to study the irradiation damage mechanism of titanite. This paper reviews the main research achievements of titanite in recent years, which include the possible location of radioactive nuclides in its crystal structure, high temperature/high pressure-induced and radiation-induced phase transitions, infrared and Raman spectroscopy, synthesis methods, irradiation damage effect and damage mechanism, annealing induced recrystallization after metamictization, hydrogen behavior, leaching in solutions and so on. In addition, some scientific controversies, such as the crystal structure of metamict titanite in the atomic scale, the oxidation state of actinides in titanite, structural similarities or differences between metamict titanite and "glassy state titanite", the reason why high temperature cannot completely restore the crystal structure of metamict titanite, and the problem whether there is any recrystallization during low temperature hydrothermal reactions of radiation damaged titanite, are discussed and reviewed.

Abstract:Fe-Mn oxide/diatomite composite was prepared by oxidation reduction and coprecipitation techniques. The effects of raw material ratio, reaction temperature, calcination temperature and solution pH on adsorption phosphate property of composite were investigated with an analysis based on adsorption isotherm, XRD and IR. The results indicate that adsorption capacity of composite prepared from 2.5 g diatomite, 1.0 mmol manganese, 3.0 mmol ferric iron and 3.0 mmol iron (Ⅱ) is 10.84 mg/g under the condition of 20℃ and pH equal to 6, increasing 3.6 times compared with diatomite. Precipitation reaction temperature is negligible and calcination of 400~500℃ is beneficial to adsorption. Adsorption capacity decreases with increase of pH, and inner-sphere complexing and electrostatic attraction on surface are jointly driving force for adsorption of phosphorus at lower pH. At high pH, inner-sphere complexing and electrostatic attraction decrease, co-adsorption with inner-sphere complexing promotes adsorption, and the total effect is the declining of phosphorous adsorption. Adsorption isotherms are well consistent with Langmuir and D-R equation and R-P equation, the saturation adsorption capacities are 34~37 mg/g and the average adsorption energies are 9.9~11.3 kJ/mol,revealing single and multiple layers adsorption with the coexistence of physical and chemical actions.

Abstract:In this research, mineral inclusions in emeralds from Malipo, Yunnan Province, are studied by polarized microscope, electron probe(EPMA), and cathodoluminescence(CL). The results show that there are several kinds of mineral inclusions which can be considered as origin characteristics in emeralds from Malipo, Yunnan Province, such as black dravite, vanadium muscovite, zonal feldspar, arsenopyrite, magnesium biotite, scheelite. Both in pegmatite veins and shear zone veins, emeralds contain feldspar, albite, dravite, fluorite, emerald (beryl), biotite, sphene, apatite, pyrite, chlorite, epidote. Inclusions only appear in emeralds from pegmatite veins are muscovite, calcite, quartz, zircon, arsenopyrite, sphalerite, galena, diopside. Inclusion only appears in emeralds from shear zone veins is scheelite. This research on different inclusions in emeralds from pegmatite veins and shear zone veins is meaningful not only for emerald identification of origin, but also reveals the genetic type of Yunnan emeralds.