Abstract:The Nuoergong Group, a suite of low-grade metamorphic strata composed mainly of quartzite, leucoleptite, carbonate and clastic rocks, was traditionally considered overlying directly the metamorphic basement named "Alxa Group" in eastern Alxa Block. Its formation age was identified as Changchengian based on regional stratigraphic correlation and stromatolites fossils. In order to precisely constrain the stratigraphic time, the authors present LA-MC-ICP-MS zircon U-Pb dating results for samples of three quartzite bodies from the lower Nuoergong Group. These zircon ages are mainly concentrated in the 2 530~2 500 Ma and 1 950~1 850 Ma, while a few zircons have ~1.69 Ga, ~2.0 Ga, ~2.15 Ga, ~2.35 Ga, ~2.7 Ga and ~3.4 Ga ages. The youngest zircon grain of 1.69 Ga indicates that the lower Nuoergong Group was accumulated after ~1.69 Ga. In combination with previously obtained ages of overlying strata, the authors have reached the conclusion that the deposition age of Nuoergong Group is between 1.69 Ga and 1.29 Ga and there exist the Meso-proterozoic strata in Alxa Block. The most prominent ~2.5 Ga and ~1.95 Ga age peaks suggest its affinity with the North China Craton. Therefore, it is held that they have similar tectonic environments and the Alxa Block was a part of North China Craton from Archean to Mesoproterozoic.

Abstract:The Longsheng area in northern Guangxi lies in the western segment of the Jiangnan Orogen. In this paper, the authors determined the chemical compositions of the clinopyroxene and plagioclase in the Jinche gabbro by electron microprobe analysis. It turns out that the clinopyroxene is augite with Wo_27~28En_47~57Fs_15~22, and the plagiolcase is albite with An_1.35~9.05Ab_90.34~97.45Or_0.36~1.05 in composition. The crystallization temperature and pressure of clinopyroxene were estimated by the clinopyroxene-melt equilibrium and clinopyroxene isotherm, which yielded crystallization temperature, pressures and corresponding formation depth of 1 250~1 350℃, 1.31~2.25 GPa and 43.2~74.3 km, respectively. The temperature is consistent with that of the asthenosphere lithospheric mantle (1 280~1 350℃), and under that depth, the decompression melting of the asthenosphere lithospheric mantle can occur. Therefore, it is inferred that the Jinche gabbro might have originated from the asthenosphere lithospheric mantle. In addition, the chemical composition of the clinopyroxene indicates that the Jinche gabbro belongs to the tholeiitic series formed in an intraplate tectonic setting. In conclusion, the authors hold that the Jinche gabbro was formed by partial melting of the upwelling asthenosphere mantle due to rifting.

Abstract:Retrograded eclogites from Mengku area contains massive amphiboles, which formed in late period of the remetamorphic process. It could keep a record of petrogenetic information in the late remetamorphic period. Based on a study of systematic mineralogy, the authors identified three periods of amphiboles and furthermore divided them into ten types. They mostly belong to calcium amphiboles such as tschermakite, ferrotschermakite, magnesiohornblende, ferrohornblende, magnesiohastingsit, ferropargasite, tremolite and actinolite, with some sodic-calcium amphiboles such as barroisite and winchite. Studies show that the formation environment of amphiboles gradually changed from reduction through weak oxidation to oxidation in the remetamorphic process. The numerical values of temperatures and pressures were computed on the basis of electron microprobe data in this paper. Combined with petrographic data, three periods of retrograde metamorphism were recognized. The first period could be divided into two stages: the early was approximately isothermal and decompression process, p=0.56~0.75 GPa and t=642~709℃, forming ferropargasite and ferrotschermakite; the latter was an isothermal and decompression process, p=0.39~0.56 GPa and t=619~642℃, forming tschermakite. The second period was a cooling and decompression process, p=0.23~0.42 GPa and t=460~610℃, forming magnesiohornblende. The third period was a isothermal and decompression process, p=0.09~0.31 GPa and t=350~420℃, forming tremolite and actinolite. The composition variation of amphiboles indicates a gradual cooling and decompression process, in which retrograded eclogites moved from crust bottom (amphibole-eclogite facies-high pressure-granulite facies) to mid-upper crust (hornblende facies, green-schist facies). The process corresponded to Indosinian collision orogenesis, Yanshanian regional crustal extension and Himalayan intracontinental orogenesis in Changning-Menglian belt.

Abstract:In this paper, the authors conducted a study of the features of cell parameters and infrared spectroscopy of quartz and cassiterite at different ore-forming stages in the Lailishan tin deposit of Yunnan Province by using X-ray powder diffraction and infra-red spectroscopy and on the basis of detailed field investigation and petrographic research, so as to interpret the genetic information of quartz and cassiterite. The results show that the hydrothermal mineralization period of the tin deposit can be divided into four stages, i.e., mica-pyrite-topaz-granular cassiterite stage (Ⅰ), mica-quartz-pyrite-columnar cassiterite stage (Ⅱ), quartz-pyrite-radial cassiterite stage (Ⅲ) and fluorite-quartz-pyrite-sphaerolitic cassiterite stage (Ⅳ). From stageⅠ to Ⅳ, the values of a₀, c₀, V₀ and the c₀/a₀ ratios of the cell parameters in quartz show a decreasing trend. Axis ratio of the rate of change in quartz is from 0.773 07 to 3.496 88; the absorbance of each absorption peak of the infrared spectroscopy in quartz tends to increase. The authors infer that quartz mainly has substitution impurities such as Al³⁺ and Fe³⁺ at stage Ⅰ and Ⅱ, has substitution impurities and interstitial impurities at stage Ⅲ, which is complicated, and has interstitial impurities such as Na⁺, K⁺ at stage Ⅳ. The values of a₀, c₀ and V₀ decrease firstly and then increase in cassiterite with the evolution of the ore-forming stage, and are smallest at stage Ⅱ, which is consistent with the changes of the total amount of impurity elements in cassiterite at different ore-forming stages. These phenomena suggest that changes of cell parameters in cassiterite are mainly affected by mixed impurity elements in lattice rather than temperature. The characteristic infrared spectra of cassiterite at different ore-forming stages are similar and belong to the deformation spectra, implying the characteristics of cassiterite-sulfide hydrothermal deposits. Moreover,the composition of hydrogen and oxygen isotopes in quartz shows that the ore-forming fluid is a mixture of magmatic and meteoric water, and the initial ore-forming fluid is derived from magma. With the evolution of hydrothermal solution, meteoric water enters hydrothermal solution along the tectonic fissures, which makes the isotopic composition of hydrogen and oxygen shift to atmospheric water.

Abstract:The Jinding giant Zn-Pb polymetallic deposit, located in Lanping County, western Yunnan Province is one of the most important mining areas of lead and zinc resource in China. The continuous active mining has induced increasing heavy soil pollution in and around this area since the 1980s, and is an ideal region to analyze the mining environmental problems. Based on the field work and sample collection, the authors measured the content of four heavy metals of zinc, lead, arsenic, cadmium in 77 soil samples and analyzed the sensitive bands of these heavy metals and their occurrences within soil clay minerals, iron-manganese oxides and carbonates. On such a basis, the Multiple Linear Regression Models (MVLR) was constructed between these four kinds of heavy metals and their measured spectra of the soil. Some results have been obtained: ① the values of the four kinds of heavy metals in this area all exceed the standard values, and show significant correlations; ② the values of these heavy metals have a high correlation with the soil spectral reflectance, the first-order differential equation of the reflectance and the continuum removed variables; ③ the accuracies (R²) of the fitting models are higher than 0.816, which proves that the predicting heavy metal content based on the measured spectra is feasible and reliable. So, the results can provide a technical support for retrieving the heavy metal content of soil by hyperspectral remote sensing technology and for mapping soil heavy metal pollution on large scale by satellite or aerial remote sensing technology.

Abstract:The primary hydrocarbon source rocks of Yabei depression in Qiongdongnan basin are coal measures of Yacheng Formation. On the basis of the theory that depositional environment controls the formation of coal measures source rocks, the depositional environments and controlling factors of coal measures source rocks were studied, and the development models of coal measures source rocks were established. The depositional environments of coal measures source rocks were saline-reducing peat swamps of the braided river delta plain and saline-oxidative peat swamps of tidal flat. The controlling factors of coal measures were depositional environments which governed the abundance and types of organic matters, microscopic constituents, and thickness of coal measures, paleo-climate which provided material background for the development of source rocks, sea level which controlled the distributive characteristics of coal measures within the strata and the perversion condition, and paleo-structure which determined formation and evolution of specific basins. There are two development models of coal measures source rocks of Yacheng Formation in Yabei depression: one is peat swamps of tidal flat in which the reduction played the leading role; the other is peat swamps of the braided river delta plain in which the high productivity was the most effective factor.

Abstract:Spinel-type minerals can be classified into normal, inverse and disordered structure according to the different proportions of cation site occupancy at metal-oxygen tetrahedron and octahedron. In this paper, the authors chose micron-scale franklinite (ZnFe₂O₄) as the original research object. Mineralogical, thermal and magnetic measurements, such as SEM, XRD, XAFS, DTA-TGA, M-H, ZFC-FC, were employed to investigate the influence and mechanism of high temperature on the cation site occupancy. The results show that the cationic exchange occurs between ZnⅡ and FeⅢ in tetrahedral and octahedral sites, respectively, along with the increasing temperature. The maximum exchange rate appears at around 910°C. Thermodynamic and kinetic equilibrium is realized after the sample is heated at 1 200℃ for 24 hours. The cell parameter (a) decreases from 8.440 7 Ǻ to 8 437 2 Ǻ, and the Neel temperature (T_N) increases from 13 K to 27 K, changing antiferromagnetic order into the ferrimagnetic one. The particle size influences the energy of system, causing the completely opposite performance of cationic exchange for micro-ZnFe₂O₄ and nano-ZnFe₂O₄ at high temperature.

Abstract:In situ X-ray diffraction patterns of the powder hematite polymorphs were recorded in a temperature range from room temperature (RT) to 1 000℃ in static air and vacuum. Lattice parameters for hematite (RT~1 000℃) in static air and vacuum were refined. The variations of lattice parameters of hematite with temperature were therefore well described. Linear (α) and volume (β) thermal expansion coefficients of hematite (RT~1 000℃) were calculated. The change laws of α and β with temperature for hematite in static air and vacuum were summarized. It is shown that linear (α) and volume (β) thermal expansion coefficients of hematite (RT~1 000℃) are constant with increasing temperature. The thermal expansion coefficients for hematite are α_a=9.603 16×10^-6/℃, α_c=6.647 67×10^-6/℃, β=2.606 33/℃ in static air and α_a=9.006 79×10^-6/℃, α_c=6.891 23×10^-6/℃, and β=2.511 51/℃ in vacuum.

Abstract:In this study, the authors improved osmosis device on the basis of previous researches. Through the self-made multifunctional osmotic swelling meter in a nitrogen pressure of 1.0 MPa, and under different conditions of content, coefficient of load, compacted density, and water breakthrough time pressing, the authors obtained the permeability coefficient of zeolite-bentonite-pyrite mixture and attapulgite-stone-bentonite-pyrite mixture for two groups of samples. The results showed that the permeability of the integrated backfill material changed little with time, and was basically consistent with Darcy's law. Under the same dry density and water content rate conditions, with the increase of the content of bentonite, the permeability coefficient of different mixed minerals decreased. When bentonite content proportion in zeolite mixture or attapulgite stone minerals was not less than 60%, the permeability coefficient satisfied the requirement of less than 7×10^-10 m/s permeability coefficient in high-level radioactive disposal of backfill material. Under the same conditions, because the zeolite is characterized by non-sticky property, large porosity, and good permeability, the water in the zeolite mixture permeated faster than that of the mixture. In the same dry density and water content rate, the greater the compaction of the loads of different mixtures, the smaller the permeability coefficient, and vice versa. From loads of 50~100 MPa, the permeability coefficient changed little. Thus, the study of the permeability characteristics of the mixture of different ratios and different influence factors, could provide a theoretical basis for the construction of a new type of cushion backfill material in the future.

Abstract:Clayey dolomite is a kind of weakly consolidated sedimentary rock with rich and open holes and high chemical activity from Cenozoic. As a useful environmental engineering material, it deserves further study. This paper discusses the effect and mechanism of the removal of lead ions from aqueous solutions by clayey dolomite. A series of experiments were designed for studying kinetic parameters (time impact), the rate of solid and aqueous concentration, and initial concentration in solutions which may influence and change the effect of removing lead ions. The results show that the equilibrium time of removing lead ions depends on the initial concentration of lead solutions. The equilibrium time is longer when the initial concentration is higher. 100 mg/L lead solution basically demands 70 hours to reach the equilibrium position. In addition, the effect of removal is controlled by final pH. A higher pH value gives rise to a more thorough removal during the process. A higher solid-aqueous rate and higher pH value can improve the removal efficiency. The main mechanism of removal is that lead ions are induced to deposition by clayey dolomite, and meanwhile hydrocerussite is produced after dolomite dissolution.

Abstract:Desulfovibrio vlugaris miyazaki SRB and Acidiphilumcryptum JF-5 are two common reductive microorganisms in the wastewater and sediments of acid mines. The two bacteria were used to synthesize the nano FeS and coat it on the surface of limestone. Dissolution kinetics experiments were conducted to investigate the influence of different nanometer FeS cladding layers on limestone dissolution and neutralization capacity, and dissolving model was set up based on the Frick's first law. The result of X-ray diffraction of coating layer on limestone surface indicates that it is mackinawite. The photoelectron spectroscopy (XPS) result further shows that the valence of Fe in coating layer is +2, and S valence is -2, the coating layer has obvious passive effect on the dissolution of limestone, the neutralization capability decreases with the increase of the layer's thickness, and the existence of the thick coating layer can make the final pH decrease to 1.5 pH compared with the final pH 6.5 of pristine limestone. The dissolution behavior of limestone in the presence of the coated mackinawite can be described as n_Ca,sol=At^1/2-n_Ca,grp, in which n_Ca,grp value could represent the amount of secondary CaSO₄ formed on the surface.

Abstract:Luonan area of Shaanxi Province is a historic site of turquoise and is a potential source of neolithic turquoise products. The texture and structure of turquoise from Luonan area of Shaanxi Province were studied by microscope, SEM, XRD experiments in this paper. The results show that the turquoise from Luonan area of Shaanxi Province mainly has cryptocrystalline texture, with some samples exhibiting band texture and nodular texture, and has lumpy structure, dense lumpy structure and minor grape structure. The observation under SEM shows that the turquoise is mainly of flaky texture and irregular lumpy distribution. Tabular turquoise microcrystals are distributed irregularly, and pores can be seen among them. The microcrystals of turquoise are somewhat anhedral, the less pores they have, the evener their arrangement, and the denser their texture, thus exhibiting dense massive structure. On the contrary, it has grape structure. XRD results show that all the samples have turquoise and quartz, and some samples contain small amounts of illite and kaolinite.

Abstract:After HPHT treatment using the cubic-anvil press, the brown diamond was investigated by spectral analysis, followed by color changing mechanism analysis. The results show that brown diamond including ⅠaA and IaAB becomes yellow 30 minutes later under the condition of 5.6 GPa and 1 650℃, which is mainly related to H3, H4, N3 centers and single nitrogen; then it will become yellowish green after HPHT treatment, which is related to H2, H3 centers.