Photocatalytic Reduction of Cr~Ⅳ by Natural Sphalerite Suspensions under Visible Light Irradiation

The photocatalytic reductive capability of a natural semiconducting mineral, sphalerite has been studied for the first time. The sphalerite from the Huangshaping deposit of Hunan Province performed great photoreductive capability that 91.95% of the Cr6+ was reduced under 9 h visible light irradiation, higher than the 70.58% under 9.5 h UV light irradiation. The highly reductive ability results from its super negative potential of electrons in the conduction band. Furthermore, Fe substitution for Zn introduces donor states, and the oxidation process of Fe2+ to Fe3+ makes it an effective hole-scavenger. Cd and Cu substitute for Zn also reduce the bandgap and help broaden the absorbing edge towards the visible light. These substituting metal ions in natural sphalerite make it a hyper-active photocatalyst and very attractive for solar energy utilization.     

Haitaite-(La), LaU4+Fe3+2(Ti13Fe2+4Fe3+)Σ18O38, a New Member of the Crichtonite Group

Haitaite-(La), (La, Ce)(U4+, U6+, Fe2+)(Fe3+, Al)2(Ti, Fe2+, Fe3+)18O38, is a new member of the crichtonite group. It is named after the Haita Village in the Miyi County of Sichuan Province, China, where the mineral was discovered. The mineral occurs as black opaque centimeter-sized aggregates in the external contact zone between the Neoproterozoic (~800 Ma) alkali feldspar granite and the Mesoproterozoic (~1700 Ma) micaschist. In the studied sample, haitaite-(La) is associated with other minerals, including ilmenite, magnetite, rutile, zircon, brannerite and uraninite. The new mineral is a black, metallic phase and has a Mohs hardness of 6, with a density of 4.99 g/cm3 (calculated) and 5.03 g/cm3 (measured). Haitaite-(La) is opaque in transmitted light and grayish-white under reflected light, with a reflectivity between 22.5% and 16.42% in the 400–700 nm band (SiC, in the air). The compositions of the mineral were measured by EPMA, the U4+/U6+ ratio was determined by X-ray photoelectron spectroscopy and the Fe2+/Fe3+ ratio was determined by M?ssbauer spectroscopy. Haitaite-(La) is trigonal, belongs to R3ˉ and has unit-cell parameters a = 10.3678(5) ?, c = 20.8390(11) ?, V = 1939.9(2) ?3, Z = 3. The crystalline structure is composed of octahedra with 9 layers of close-packed octahedra (M1, M3, M4, M5), tetrahedra (M2) and contains large 12-coordinated M0 sites.     

Photocatalytic Reduction of Cr^Ⅵ by Natural Sphalerite Suspensions under Visible Light Irradiation

The photocatalytic reductive capability of a natural semiconducting mineral, sphalerite has been studied for the first time. The sphalerite from the Huangshaping deposit of Hunan Province performed great photoreductive capability that 91.95% of the Cr^6＋ was reduced under 9 h visible light irradiation, higher than the 70.58% under 9.5 h UV light irradiation. The highly reductive ability results from its super negative potential of electrons in the conduction band. Furthermore, Fe substitution for Zn introduces donor states, and the oxidation process of Fe^2＋ to Fe^3＋ makes it an effective hole-scavenger. Cd and Cu substitute for Zn also reduce the bandgap and help broaden the absorbing edge towards the visible light. These substituting metal ions in natural sphalerite make it a hyper-active photocatalyst and very attractive for solar energy utilization.     

A New Martian Meteorite from Antarctica:Grove Mountains (GRV) 020090

Reported in this paper are the petrology and mineral chemistry of GRV 020090, the second Martian meteorite collected from the Grove Mountains, Antarctica. This meteorite, with a mass of 7.54 g, is completely covered by a black and glazy fusion crust. It has two distinct textural regions. The interstitial region is composed of euhedral grains of olivine, pigeonite, and anhedral interstitial maskelynite, with minor chromite, augite, phosphates and troilite. The poikilitic region consists of three clasts of pyroxenes, each of which has a pigeonite core and an augite rim. A few grains of subhedral to rounded olivine and euhedral chromite are enclosed in the pyroxene oikocrysts. GRV 020090 is classified as a new member of lherzolitic shergottites based on the modal composition and mineral chemistry. This work will shed light on the composition of Martian crust and magmatism on the Mars.     

The Discovery of Magnesioferrite from Au (Fe, Cu) Magnesian Skarn Deposits and Study of the Magnesioferrite-Magnesiomagnetite Series

Magnesioferrite, a rare metasomatic mineral, was discovered for the first time in China from the Qinlou Au (Fe, Cu) magnesian skarn deposit, Sanpu, Huaibei, Auhui Province, and the Mulonggou Fe (Mo, Cu) magnesian skarn deposit, Luonan County, Shaanxi Province. In this paper, the geological setting, mineral associations, chemical composition, some physical properties, X-ray powder diffraction data and infrared spectroscopy of magnesioferrite and magnesiomagnetite are discussed. Magnesioferrite contains 17.66%-13.48% of MgO. Its main associated minerals are clinohumite, chondrodite, serpentine,, calcite and magnesiomagnetite. The density of magnesioferrite is 4.537-4.720, reflectances in percent are: 17.8-18.1, hardness is 838-900 kg/mm2, and the cell parameter a0 = 8.371-8.379 A. A systematic study of the magnesioferrite-magnesiomagnetite-magnetite series suggests that along with the increase of magnesioferrite molecules in the mineral, the density, reflectances and cell parameters decrease corresponding     

Biogeochemical Study of Tamarix Aphylla from Lasbela Area and Its Application in Prospecting of Ore Deposits

Biogeochemical investigation of Tamarix aphylla,a plant species, of the Las-bela area has been made.This area mainly consists of ophiolites associated with sed-imentary rocks of Jurassic and Cretaceous age .Quantitative estimations of important biogenic trace elements such as Fe,Mn,Pb,Zn,Cu,Cr,Ni, and Co have been carried out .Anomalous concentrations of these elements in plant species of certain regions can be used to locate possible occurrences of ore deposits in the area.The comparative strdy also reveals appreciable variations in the composition of trace elements in plants.The possible causes of variation in the constitrents of Tamarix aphylla from different localities have been discussed in the light of bed rock nature, mo-bility of element and average abundance in the plant.     

Mineral Geochemical Compositions of Tourmalines and Their Significance in the Gejiu Tin Polymetallic Deposits, Yunnan, China

Abstract: The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schorl with Fe/(Fe+Mg) ratios of 0.912-1.00 and Na/(Na+Ca) ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/(Fe+Mg) ratios of 0.212-0.519 and Na/ (Na+Ca) ratios of 0.786-0.997. Tourmalines from the country rocks are dravite with Fe/(Fe+Mg) ratios of 0.313-0.337 and Na/(Na+Ca) ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/(Fe+Mg)=0.374-0.843, Na/(Na+Ca)=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.     

Distribution and Geochemical Characteristics of Hydrogen in Natural Gas from the Jiyang Depression, Eastern China

Hydrogen gas accelerates hydrocarbon generation, but little is known about its distribution and origin in petroliferous basins, which has hindered the further exploration.Taken the Jiyang Depression in eastern China as an example, this study collected natural gas from different tectonic units, and analyzed various geochemical characters including gas contents, and carbon and hydrogen isotopic composition.The result shows that:(1) hydrogen gas is widespread distributed, but its content is very low, which typically ranges from 0.01% to 0.1% in this region;(2) the ratios of H2/3He, indicative of the origins of hydrogen gas, suggest that mantle-derived hydrogen is dominant.Even in tectonically stable areas absent with deep fluid activities, there is also mantle-derived;(3) the isotopic composition of hydrogen falls in the range of –798‰ to –628‰(relative to VSMOW standard).In areas with deep-derived fluids, the hydrogen gas has a similar isotopic composition with the previously documented deep-sourced gas, with lighter isotopic composition.In contrast, hydrogen gas has a heavier isotopic composition in relatively stable areas.The isotopic signatures suggest that there is a mixture of mantle- and crust-derived hydrogen gas in the relatively stable area, which is consistent with the H2/3He ratios.Therefore, it is clear that the hydrogen gas has a much wider distribution than found in the deep-derived fluid area, resulting in a much broader area with hydrogenating effect for resource rock.This understanding will provide new insights for hydrocarbon generation research and resource assessment in petroliferous basins.     

Mineral Deposit Model of Cu–Fe–Au Skarn System in the Edongnan Region, Eastern China

Cu and Fe skarns are the world’s most abundant and largest skarn type deposits, especially in China, and Au-rich skarn deposits have received much attention in the past two decades and yet there are few papers focused on schematic mineral deposit models of Cu–Fe–Au skarn systems. Three types of Au-rich deposits are recognized in the Edongnan region, Middle–Lower Yangtze River metallogenic belt: ~140 Ma Cu–Au and Au–Cu skarn deposits and distal Au–Tl deposits; 137–148 Ma Cu–Fe; and 130–133 Ma Fe skarn deposits. The Cu–Fe skarn deposits have a greater contribution of mantle components than the Fe skarn deposits, and the hydrothermal fluids responsible for formation of the Fe skarn deposits involved a greater contribution from evaporitic sedimentary rocks compared to Cu–Fe skarn deposits. The carbonate-hosted Au–Tl deposits in the Edongnan region are interpreted as distal products of Cu–Au skarn mineralization. A new schematic mineral deposit model of the Cu–Fe–Au skarn system is proposed to illustrate the relationship between the Cu–Fe–Au skarn mineralization, the evaporitic sedimentary rocks, and distal Au–Tl deposits. This model has important implications for the exploration for carbonate–hosted Au–Tl deposits in the more distal parts of Cu–Au skarn systems, and Fe skarn deposits with the occurrence of gypsum-bearing host sedimentary rocks in the MLYRB, and possibly elsewhere.     

某地含黑稀金矿花岗岩脉的初步研究

An investigation has been conducted of the geological and geochemical characteristics of euxenitebearing granitic veins found for the first time in China. It is shown that these veins are late intrusives in an Yah Shah granitic complex at a geosyclinal folded zone and composed mainly of medium grained biotite granite in which the local enrichment of euxenite during the late period of magmatic activity is obvious. The mineral has been found to be metamiet and chemically represent a transitional member between euxenite and polyclase. This study has provided a typical example that gralitic melts with a lower initial content of rare elements would contribute significantly to the local enrichment of rare element minerals under special external conditions.     

Diatomaceous deposits of Fayium, Egypt; characterization and evaluation for industrial application

The Holocene lacustrine diatomaceous earth of Fayium,South West of Cairo,has been studied to define its minerals,chemistry,petrography and physical properties.Minerals were processed by way of calcination at 550℃ ,followed by acid leaching to reduce levels of mineral impurities.The diatomite is of biogenic opal A.with calcite as the main ganue mineral,quartz and clay minerals(smectite followed by kaolinite in abundance and a trace amount of illite).Silica in the diatomaceous earth accounts for about 63% on average.Positive correlation between CaO and CO2 indicates that Ca is present mainly as calcite.Al2O3,Fe2O3,MgO and K2O are attributed mainly to clay minerals.However,the physical properties of the diatomaceous earth as filter-aids and filler for paints and plastics are poor because of general high levels of impurities.The technological performances of the diatomaceous earth have been significantly improved owing to upgrading of diatoms through mineral processing trical.     

Geochemical assessment of a siliceous limestone sample for cement making

A low grade siliceous limestone sample from the Jayantipuram mine of Andhra Pradesh, India, has been investigated for its suitability for cement making. Petrological as well as X-ray diffraction pattern studies indicated that the limestone sample was crystalline and dominantly composed of calcite and quartz. They are simple in mineralogy, and yet they have variable silica and lime contents. Geochemical analysis results of twenty five hand picked samples indicated that the limestone from the Jayantipuram mine shows a wide range of variations in LOI (29.94% to 40.64%), SiO2 (6.14% to 27.18%), CaO (37.93% to 50.78%), Al2O3 (0.49% to 2.27%) and Fe2O3 (0.28% to 2.4%). MgO, K2O, Na2O, TiO2 and MnO2 are present in traces. CaO with LOI shows a strong positive correlation where as CaO with SiO2 shows a strong negative correlation because of mineralogical factors. The chemical composition of the limestone reflects its mineralogical composition. The distribution of various elements in the acid-soluble fraction has been studied by the factor analysis method in order to interpret in terms of their mineralogy, sedimentary environment and diagenesis. Mineralogy, recrystallization and other diagenetic changes are the main factors affecting the distribution of the elements and their mutual relationships in the limestone. The aim of this paper is also to analyze how significantly the two parameters, silica modulus and lime saturation factor, influence this low grade siliceous limestone sample from the Jayantipuram mine of Andhra Pradesh, India, for the cement making process from the geochemical data.     

Trace Element Geochemistry of Magnetite from the Fe(-Cu) Deposits in the Hami Region, Eastern Tianshan Orogenic Belt, NW China

Laser ablation–inductively coupled plasma–mass spectrometry(LA–ICP–MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(–Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni–Mn–V–Ti(Factor 1), Mg–Al–Zn(Factor 2), and Ga– Co(Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(–Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(–Cu) deposits may be related to felsic magmatism.     

Study on the Crystal of Daomanite

It was not possible to carry out a complete analyses of crystal, as the experiment by Ding and Shi et al.. It's analysis precision R=0.25 or more big than this, which value are not satisfied for single crystal study, but we through many test and found the best: [R(int)=14.5%]. The final fullmatix least-squares refinement on F2 converged to R1=0.0791 and wR2=0.1864 for 704 observed reflections [I 3 2s(I)]. Daomanite is orthorhombic system, space group Cmc21, a=3.7520(8))?, b=15.844(4) ?, c=5.8516(12) ?, α=β=γ=90°. V=347.86(14)?3, Z=4. Daomanite chemical formula is Cu Pt AsS 2. Idealized composition Me+M2+M2+S2=CuS ·PtA s S. There is no other similar mineral in the world.     

Biogeochemical Model and Simulation of the Effect of Precambrian Algae on the Formation Process of Certain Laminated Cherts

The source of silica in the formation of the Precambrian laminated cherts has long remained a problem to be solved. Through experiments on cherts and living blue-green algae, the authors found that the collected chert samples probably come from primary deposits, and there is a great biomass of fossil algae in chert, among which the filamentous algae can be compared with the living blue-green algae Oscillatoria, that a higher Pco_2 of the gas would be favourable for the increase of the biomass of living blue-green algae and consequently raises the pH value of the water body; and that lack of free oxygen and a higher concentration of SiO_2 in the water have no apparent influence on the biomass of blue-green algae. Based on the evidence above, a biogeochemical model concerning the origin of Precambrian laminated chert has been set up, in which the. photosynthesis of algae under the presumed atmospheric conditions of the Precambrian might raise the pH value of the water body and promote the dissolution of silicate minerals, thus providing a source of colloid SiO_2 for the formation of Precambrian laminated chert.Furthermore, a simulation experiment device has been designed successfully, which can control the temperature(30 ± 0.5°), Pco_2(50662.5 Pa) and Po_2(about zero Pa) of the gas, the rate of photosynthesis of algae and the movement of the water carrying opal. In the simulation experiments, separate measurements have been made on the rate of photosynthesis of algae, pH value and concentration of SiO_2 of the water body, with the results indicating that under the conditions similar to the presumed Precambrian atmosphere, the photosynthesis of algae can make the pH value of the water body go up steadily to over 9.7, leading to the dissolution of the silicate minerals, with the concentration of SiO_2 measured reaching as high as 84 mg/l. Finally, through the vaporation of water, a phenomenon of colloid floccilation has been observed.The simulation experiment has verified the proposed biogeochemical model illustrating the origin of Precambrian laminated chert. Moreover, the device and method of its kind may also be applied to the research on the relationship of the Precambrian algae with the formation of some other mineral deposits such as of Fe, Mn, U and carbonates.     

Biota and Organic Matter in the Late Sinian and EarlyCambrian Black Rock Series of West Hunan andIts Significance for Metallization

A great amount of black rock series has been found in the Upper Sinian Members 2 and 4 of the Jinjiadong Formation, middle-upper Liuchapo Formation and the Lower Cambrian Xiaoyanxi Formation in West Hunan, which is associated with periodic sea-level changes. By the studies of relationships between the distribution and development of the biota and the abundance of Au, Ag, U, V, Ni, Mo and Cu in the Upper Sinian and Early Cambrian black rock series in Cili, Dayong, Yuanling, Xupu and Qianyang of West Hunan, central China, it has been revealed that the enrichment of Ag, V, and Mo is related with the development of multi-cell plants and vendotaenides, and that of Cu and Ni is related to flourishing of bacteria and shelly fossils. The black rock series in the study area contains abundant organic matter, among which the siliceous shale contains the highest TOC, amounting to 4.51-13.4%. All the values of the equivalent vitrinite reflectance (medium values) determinated with the IR-spectroscopic method in the a     

金伯利岩的岩石化学特征与含金刚石程度的判别

There has been found a distinct directional trend of kimberlites differring in orebearing capability with changing chemical composition. The contents of MgO, NiO and Cr2O3 decrease gradually while Na2O3. K2O and Al2O3, as well as P2O3 increase eonsiderably in the order of diamond-rich- diamond-poor-diamond-absent kimberlites. In general, Fe2O3, FeO and TiO2 also show an increasing tendency. Therefore, the variation in chemical composition may be used as a petrochemical index for calculating the ore-bearing capability of kimberlites. Based upon discriminant analysis, it is possible to make a distinction between diamond-bearing and diamond-free, or between diamondrich and diamond-poor kimberlites.     

Thermogravimetry-differential thermal analysis coupled with chromatography as a thermal simulation experimental method and its application to gaseous hydrocarbons from different source rocks

In this paper a thermogravimetry-differential thermal analysis method coupled with chromatography （TG-DTA-GC） has been adopted to simulate the generation of gaseous hydrocarbons from different hydrocarbon source rocks such as coals, mudstones, and carbonate rocks with different maturities. The temperature programming for thermal simulation experiment is 20℃/min from ambient temperature to 700℃. As viewed from the quantities and composition of generated gaseous hydrocarbons at different temperatures, it is shown that low-mature coal has experienced the strongest exothermic reaction and the highest loss of weight in which the first exothermic peak is relatively low. Low-mature coal samples have stronger capability of generating gaseous hydrocarbons than high-mature samples. The amounts and composition of gaseous hydrocarbons generated are closely related not only to the abundance of organic carbon in source rocks, but also to the type of kerogen in the source rocks, and their thermal maturity. In the present highly mature and over-mature rock samples organic carbon, probably, has already been exhausted, so the production of gaseous hydrocarbons in large amounts is impossible. The contents of heavy components in gaseous hydrocarbons from the source rocks containing type- Ⅰ and - Ⅱ kerogens are generally high ; those of light components such as methane and ethane in gaseous hydrocarbons from the source rocks with Ⅲ-type kerogens are high as well. In the course of thermal simulation of carbonate rock samples, large amounts of gaseous hydrocarbons were produced in a high temperature range.     

Seismic Velocity Structure and Composition of the Continental Crust of Eastern China

On the basis of a one-by-one latitude-longitude grid three-dimensional seismic velocity model, the crustal P-wave velocity structure in eastern China (105-125°E and 18-41°N) is obtained, and a set of geotherms for each grid is established for P-T correction on P-wave velocities. The average depths of sub-crustal layers and their average P-wave velocities of 18 tectonic units in eastern China are exhibited. Our result presents a 32-34 km thick crust beneath eastern China, which is thinner than previous studies, with an average velocity of 6.54 km/s, corresponding to a 5 kg/m3 variation in crustal mean density. The thicker upper but thinner middle and lower crust results in a lower average seismic velocity of eastern China. An intermediate crustal composition with a SiO2 content of 59.7 wt% has been estimated. However, there exists a significant lateral variation in the crustal structures among the tectonic units of eastern China. The structure and composition features of some regions in eastern China in     

Compositional Variation and Mineral Chemistry of the Jinshajiang and Lancangjiang Serpentinites,Yunnan Province,SW China

We present the whole rock and the mineral chemical data for upper mantle peridotites from the San-Jiang region in Yunnan, SW China. These peridotites are a part of a Paleo-Tethyan ophiolite belt occurring along the Jinshajiang and Lancangjiang suture zones. All samples of the Jinshajiang and Lancangjiang ultramafic rocks are completely serpentinized. The Jinshajiang serpentinites are characterized by no relict of olivine and pyroxene, and the Cr# content of spinels is 0.32–0.49. The Lancangjiang serpentinites were collected from two different locations; the northern location which has some relict of Opx(Al2O3 is 0.13–2.2 wt%, TiO 2 is 0.004–0.057 wt% and Mg# content is 0.895–0.933) and the Cr# content of spinel is 0.26-0.55; the southern location, which has some relict of Olivine(Fo = 90–92.5 and NiO = 0.12–0.26 wt%), and spinel Cr# ranging from 0.41 to 0.57. The whole rock geochemical and the mineral chemistry data imply that the Jinshajiang and Lancangjiang serpentinites represent abyssal peridotites residues after ~15–20% partial melting for the Jinshajiang and Lancangjiang serpentinites(south location), and ~11–19% partial melting for the Lancangjiang serpentinites(north location). In addition, the compositional trends of the spinel analyses of the Lancangjiang serpentinites imply that the MORB melt-peridotite interaction process played a significant role during their evolution. These processes are evidenced by an increase in Cr# with an increase in TiO 2, whereas the spinel analyses of the Jinshajiang serpentinites display an increase in Cr# with a decrease in Ti O2, indicating that the Jinshajiang serpentinites were subjected to a simple partial melting process.