Abstract:MOR-type and SSZ-type ophiolites occur along the Dachadaban profile in North Qilian Mountains (NQM) of northwest China, which have recorded magmatic activities in different tectonic environments. Geochemical data show that the gabbro in the southern part of the profile has a pattern similar to N_MORB pattern, characterized by low SiO2 (48.04%～51.20%) and MgO (7.29%～10.81%), Mg index varying from 0.52 to 0.69, high TiO2 (1.27%～1.47%) and Al2O3 (12.66%～14.50%), and high (REE content ranging from 37.18×10-6 to 62.09×10-6, about 10 times higher than that of chondrite. The REE pattern indicates a flat distribution or slight LREE depletion relative to HREE, with （La/Yb）N ratios ranging from 0.66 to 0.80, and weak negative Eu anomalies (δEu from 0.83 to 0.91). The gabbro has similar Ti/V ratio to N-MORB, but is enriched with Rb, Ba, Th and U. Geochemical characteristics similar to N-MORB imply that the gabbro is of oceanic crust origin. Zircons separated from a gabbro sample are fine_grained (50～100 μm) and mostly have long prismatic shape. CL images show that zircons contain an oscillatory zone with Th/U ratio ranging from 0.72 to 1.18, suggesting a magmatic origin. All zircons are concordant and have an age of 505±8 Ma by SHRIMPU-Pb dating, representing the formation time of gabbro. This gabbro is coeval with the Aoyougou (504 Ma) and Dongcaohe gabbro (497 Ma) in NQM, suggesting a common oceanic spreading and formation of oceanic crust at the end of Cambrian in the North Qilian Mountain. By contrast, pillow lavas from the northern part of the profile are characterized by high SiO2 (52.33%～55.62%) and MgO (10.43%～14.17%), Mg index varying from 0.72 to 0.78, low TiO2 (0.29%～0.44%) and Al2O3 (10.10%～13.34%), and low ΣREE content (9.93×10-6～19.04×10-6), 10 times lower than ΣREE content of chondrite. The REE pattern displays LREE depletion with (La/Yb）N ratios ranging from 0.45 to 0.69. Most pillow lava samples have negative Eu anomalies (δEu ranging from 0.58 to 1.08), with distinct negative-Nb, Ta anomalies and a Ti/V ratio similar to that of arc tholeiite. The overall geochemical characteristics resemble those of boninite, which originated from an island arc related to the northward subduction of oceanic crust. Pillow lavas were formed slightly later (483 Ma), consistent with the field relationship of pillow lavas overlying gabbro. These data indicate that there is about 20 Ma time difference from the formation of oceanic crust to the production of island arc. This study provides important constraints for the evolution of ocean basin in the NQM.

Abstract:Located in central Tibet, the Gaize ophiolite is a key element within the middle part of the Bangong Co-Nujiang suture zone, marking the boundary between the Lhasa and Qiangtang blocks. It is a tectonic mélange consisting of numerous blocks of mantle peridotite, mafic lavas, isotropic gabbro and plagiogranite, in which, the genesis and tectonic setting of the plagiogranite is important in discussing the evolution of the Bangong Co-Nujiang suture zone. Based on detailed studies of field geological background and petrographical features, the authors selected some samples to analyze the whole-rock content of major elements, trace elements and rare earth elements and determine the ages of zircons separated from the plagiogranite by La-ICP-MS U-Pb method. The results show that the plagiogranite crops out as dykes intruding into gabbro, basalt and basaltic andesite with no thermal aureole along the boundary between the plagiogranite and associated lavas comprising basalt and basaltic andesite. The plagiogranite is mainly composed of quartz and plagioclase with granitice tex-ture. The content of SiO2 is high, varying in the range of 72.18%～74.55% with the Mg# of 42, and the content of Na2O and K2O is 1.30%～3.13% and 0.26%～0.67%, respectively, with high Na2O/K2O ratios ranging from 3.64 to 8.23. The chondrite normalized REE patterns of the plagiogranite are similar to those of the associated lavas with flat pattern and weak negative anomaly of Eu (δEuN=0.82～0.95). La and Yb versus SiO2 correlations of the plagiogranite and associated lavas and isotropic gabbro reveal that the plagiogranite resulted from the magma remelting from the associated lavas. Like the associated lavas, the plagiogranite rocks have island arc affinity with HFSE depletion and LILE (Sr, Rb) enrichment, and Nb, Ta and Ti negative anomalies in chondrite-normalized plots indicate that these rocks might have originated in the suprasubduction zone setting. Thus, the plagiogranite and the associated lavas are considered to be members of the SSZ-type ophiolite. The grains of zircons separated from the plagiogranite are about 40～60 μm in length, with no residual old nuclear and metamorphic edge but the development of banded structure. The values of Th/U between 0.32 and 1.38 (higher than 0.1) suggest that they are magmatic zircons. The average age of zircons in the plagiogranite is 189.8±1.9 Ma, suggesting that the plagiogranite was formed in early Jurassic. The evidence of geochemistry and U-Pb age supports the hypothesis that the subduction occurred at the early Jurassic period in Gaize area within the middle part of the Bangong Co-Nujiang suture zone, earlier than the subduction in the Bangong Co area within the western part of the suture where the activity took place in mid-Jurassic time, but later than the subduction in the Dingqing area within the eastern part of the suture where the activity happened in late Triassic. Combined with previous studies, the authors believe that the Bangong Co-Nujiang Tethys subduction started from east to west during the late Triassic to Jurassic period.

Abstract:Located in northern Songpan-Garzê orogenic belt and intrudinginto Triassic Xikang Group mainly comprising sandstone and slate, the Hongyuan granites are composed of medium-fine grained granodiorite and monzogranite. Geochemical analyses show that they have high SiO2 (62.36%～73.7%) and Al2O3 (13.84%～16.69%) content, low TiO2 (0.18%～0.72%), Na2O (2.64%～4.43%) and K2O (2.24%～5.07%) content, and similar Na and K content.These granites are of metaluminous-peraluminous high-K calc-alkaline series and can be mostly classified as I type granite (some Yanggonghai and Dagaizhai granites can be classified as A type granite). Their total REE amounts vary considerably (84.39×10-6～241.07×10-6). Light REE elements are of relative enrichment. They are enriched with large ion lithophile elements such as Ba, Rb and Th and depleted in high field strength elements like Nb and Ta. In chondrite_normalized REE patterns，all samples are LREE-enriched with insignificant Eu anomalies (δEu=0.54～1.28). Light and heavy REE are significantly fractionated. The fractional extent of light REE［(La/Sm)N=6.13～11.16］ is higher than that of heavy REE ［(Gd/Yb)N=2.13～9.52］LA-ICP-MS U-Pb zircon ages (211.0±0.11 Ma) of the granites suggest that their intrusion occurred in late Indosinian. The melt composition is different in different source positions. It is thought that these granites most likely resulted from partial melting of the homologous crust, and that there was a substantial proportion of biotite in the source region because they were metaluminous-peraluminous high-K calc-alkaline granites with high SiO2 and Rb content and relatively high K2O/Na2O ratio. They were probably derived from metamorphic greywacke and intermediate volcanic rocks. Based on Hf－Rb/10－Ta×3 triangular diagram and Rb－(Y+Nb) discrimination diagram, the authors have reached the conclusion that the granites might have been formed in an collision environment after the main intracontinental collision and required an underplating or intraplating scheme of mantle-derived magma.

Abstract:Located in the southern margin of South Qinling belt, the Dalangshan Group is a series of volcanic sedimentary rocks and exposed well in Xinyangdain area of Suizhou City, Hubei Province. To find out the diagenetic age of the Dalangshan Group and provide credible time information on the materials in “Qinling microplate", the authors carried out a detailed fieldwork on Dalangshan Group and collected representative schist samples to study petrography and LA-ICP-MS zircon U-Pb geochronology. The schist mainly consists of quartz (60%～65%), muscovite (30%～35%) and plagioclase (～3%). The cathodoluminescence (CL) images reveal that most zircons from the schist are euhedral with oscillatory internal zoning, but a few grains display no zoning/weak zoning suggesting metamorphic origin. LA-ICP-MS zircon analyses show that 2 in 30 spots of these zircons have relatively high content of Th (820×10-6， 888×10-6) and U (1024.47×10-6，1146.97×10-6), but others have low content of Th (25×10-6～481×10-6) and U (34.60×10-6～752.10×10-6). Except for six points with Th/U ratios ranging from 0.22～0.39, Th/U ratios all range from 0.42 to 1.41. Most zircon U-Pb ages from the schist are between early and middle Neoproterozoic (884～758 Ma) and could be divided into four groups, indicating that at least four tecto-thermal events occurred in the south Qinling region during this period. The first group of 6 spots yield 206Pb/238U ages between 758 Ma to 769 Ma with a 206Pb/238U weighted average age of 765±6 Ma (MSWD=0.31); the second group of 8 spots yield 206Pb/238U ages between 781 Ma to 802 Ma with a 206Pb/238U weighted average age of 791±6 Ma (MSWD=1.4), suggesting that both of them may be relevant to the breakup of Rodinia supercontinent. The third group of 9 spots yield 206Pb/238U ages between 818 Ma to 840 Ma with a 206Pb/238U weighted average age of 831±6 Ma (MSWD=1.2); the fourth group of 4 spots yield 206Pb/238U ages between 870 Ma to 884 Ma with a 206Pb/238U weighted average age of 879±9 Ma (MSWD=0.52), implying that both of them may be relevant to the convergence of Rodinia supercontinent. The scattering of LA-ICP-MS zircon U-Pb ages suggest that the zircons from the schist of Dalangshan Group are detrital zircons and have not been obviously influenced by later greenschist-facies metamorphism. All of the four groups of zircon ages are concentrated in the Neoproterozoic, indicating that the formation of the schist in the Dalangshan Group should not be earlier than Neoproterozoic. A spot with 2500 Ma age implies a possible tecto-thermal event in the South Qinling region during late Neoarchean to early Paleoproterozoic period. The LA-ICP-MS zircon U-Pb ages of schist in combination with the stratigraphy suggest that the Dalangshan Group was formed in early Sinian.

Abstract:The Daixian rutile deposit is located in western Hengshan and belongs geotectonically to the central zone of North China Craton. The exposed strata mainly comprise a suite of medium-grade regional metamorphic rocks of Upper Archaean Wutai Group. The rocks have undergone multi－stage amphibolite facies metamorphism and deformation. Recent exploration shows that the Daixian rutile deposit is one of the largest rutile deposits in China with reserves up to 3.7 million tons of TiO2. The Hongtang rutile orefield is one of the three main orefields in the Daixian rutile deposit. The rutile-bearing rocks mainly include anthophyllite schist, vermiculitized antinolite schist, albite-clinochlore-bearing antinolite schist and vermiculitized actinolite-bearing quartzite. Except for one silicified sample (HT-5, quartzite), they contain 47.83%～55.03% SiO2, high MgO, TiO2 and Al2O3, low CaO, Na2O and K2O, and are depleted in LREE and roughly flat in HREE and have conspicuous negative Eu anomalies. LILE content changes slightly, and differentiation of HFSE is inconspicuous. The rocks are slightly poor in Ti, Zr, Hf, Y, and Ba, Sr, Rb. The samples with high Ti (TiO2>4%) have conspicu-ous positive Nb and Ta anomalies. The authors thus infer that the protolith of the rutile deposit is chemically equivalent to mid_ocean ridge tholeiite, and that the ore-bearing rocks were formed through crystallization differentiation of anorthite and other types of metamorphism and deformation. The growth characteristics and mineral inclusions of zircons in the ore-bearing rocks as well as U-Th-Pb ages show that the protolith of the Hongtang rutile orefield was formedaround 2530 Ma and might have experienced two regional metamorphic events with hydrothermal fluid mixture during 2370～2530 Ma and around 1900 Ma, corresponding respectively to high grade amphibolite facies and medium-pressure and low-temperature greenschist facies.

Abstract:Petrologic characteristics and analyses of major and trace elements of the amphibolites in Hualong Group within the eastern segment of Middle Qilian massif are reported in this paper. The amphibolites consist mainly of amphibole (52%) and plagioclase (40%), with the accessory minerals comprising ilmenite (6%), aprtite (2%), quartz and sphene. In the rocks, SiO2=43.78%～48.09 %, TiO2=2.26%～2.5%，Al2O3=14.99%～16.64%，P2O5=0.38%～0.43%，CaO=8.11%～10.93%，FeOt=11.83%～12.54%, and Mg#=0.53～0.54. The amphibolites in Hualong Group crop out in layers, and their protoliths are alkalic basalts characterized by significant LREE［(La/Yb) cn=4.3～8.3)］ and HFSE (e.g., Nb, Ta) enrichment (Nb/La=1.2～1.5, Th/Ta=1.2～1.4) and insignificant Eu anomalies (Eu/Eu*=0.90～1.11 , with an average of 1.04 ), as well as trace element patterns similar to those of ocean island basalts. Various geochemical diagrams indicate that these amphibolites mainly formed in an intraplate environment. Compared with OIB, amphibolites have slightly lower LILE (e.g., Th) concentrations, implying an effect of asthenosphere_lithosphere interactions. The formation of the amphibolites was probably related to the partial breakup of the Neoproterozoic Rodinia Supercontinent in the Qilianshan region or the breakup of Neoproterozoic Rodinia Supercontinent in part of the Qilianshan region.

Abstract:Large amounts of pyrites frequently found in Lower Paleozoic (especially in Ordovician) carbonates of the Tarim Basin occur in carbonate, fractures, dissolution pores, karst breccias or cave fillings of sand and mud clasts. The pyrites are present as dispersed grains with sizes up to several millimeters. Studies of the extensively existent pyrites not only can determine the process of the associated fluids but also are of great significance in discussing the origin of the extensively-concerned high concentration of H2S in natural gas within the Ordovician carbonates. In this paper, the modes of occurrence of the pyrites were described in detail and the sulfur isotope composition was analyzed. 18 pyrite samples for sulfur isotope analysis were collected from cores of different wells, among which 13 are located in the Tabei uplift, and 5 in the Tazhong uplift. According to the modes of occurrence and sulfur isotope composition, the pyrites can be divided into two groups. The first group occurs in karst breccias or in sand and mud clasts and is thought to be associated with surface meteoric karstification. The δ34S values of the first group range from -25.7‰ to -4.7‰, -17.6‰ on average. According to modes of occurrence and sulfur isotope composition, the first group is probably a product of bacterial sulfate reduction (BSR). It is thought that the BSR might have taken place under the condition of relatively low temperature when the carbonate was uplifted to surface or subsurface and altered by meteoric waters. The second group of pyrites principally occur in fractures of carbonates and are sometimes coexistent with calcite veins where the homogenization temperature of the fluid inclusions is relatively high. The values of the second group range from +11.2‰ to 31.3‰, 21.8‰ on average. The modes of occurrence and sulfur isotope composition show that the second group might be a product of thermochemical sulfate reduction (TSR). The TSR is considered to have taken place under a condition of relatively high temperature in association with magmatic activities. The sulfur involved in both BSR and TSR is thought to have originated from anhydrite or sulfate in the formation water which was extensively existent in Cambrian, Ordovician and Carboniferous strata. High concentration of H2S was found in the Ordovician carbonate which contains large amounts of pyrites. For instance, the measured concentration of H2S is up to 102908.17 mg/m3 in the natural gas produced from the Ordovician carbonate of the T740 well which is located in the main area of the Tahe oilfield in the Tabei uplift. The area with high concentration of H2S is also the area with extensive magmatic activity. According to sulfur isotope composition and its relation with the distribution of igneous rocks, the high concentration of H2S in the natural gas in Lower Paleozoic carbonates of the Tarim Basin is considered to be predominately the product of TSR.

Abstract:Before the continental collision between India and Asia, there existed widespread Early Jurassic to Eocene arc magmatism in the Lhasa Block of southern Tibet, which resulted from the northward subduction of the Tethyan oceanic lithosphere beneath Asia. This paper has reported geochronological (40Ar/39Ar dating), major and trace elements and Sr-Nd-O isotopic data of the Cretaceous volcanic rocks widely exposed in the north of the Lhasa Block and tried to investigate the tectonic evolution of the Gangdise Arc. 40Ar/39Ar geochronolo gical data indicate that these Cretaceous volcanic rocks could be divided into two groups, namely Early Cretaceous (140～110 Ma) and Late Cretaceous (100～80 Ma). Early Cretaceous volcanic rocks refer to the interbeds in Zenong Group and Duoni Formation, which are mainly distributed in such central-northern areas of the Lhasa Block as Taruoco, Coqên, Dangruoyongco and Xainza and consist of basalt, basaltic andesite, andesite, dacite and rhyolite (mostly divided into high-K and shoshonitic series and subordinately into medium-K series). The authors focused their study on the basalt and basaltic andesite of Zenong Group (SiO2=47.76%～56.25%，high-K calc-alkaline and shoshonitic series in SiO2-K2O diagram), which are characterized by relative enrichment of light rare earth elements and large-ion lithophile elements, negative Eu anomaly (δEu=0.77～0.95), negative Nb, Ta, Ti anomalies, and relatively high initial (87Sr/86Sr)t (0.7063～0.7072), low 143Nd/144Nd (0.5124～0.5126) ratios and εNd(t) (-5.4～-1.5), and high δ18OV_SMOW (7.2‰～9.8‰), indicating that the magma source was the lithospheric mantle wedge metasomatized by the fluid/melts from the oceanic sediments or/and the oceanic crust. Late Cretaceous volcanic rocks mainly consist of intermediate-basic volcanic rocks in calc-alkaline (low-K tholeiitic and medium-K calc-alkaline, SiO2=50.91%～70.45%) series, sparsely exposed inthe north of the Lhasa Block and south of the Qiangtang Block. Compared with Zenong Group volcanic rocks, these volcanic rocks are characterized by younger ages, high Mg (Mg#=59) and compatible elements (Cr=162×10-6, V=216×10-6, and Ni=80×10-6) content, relatively primitive Sr-Nd isotopic composition (87Sr/86Sr)t=0.7041～0.7049; 143Nd/144Nd=0.5125～0.5128; εNd(t)=-3.5～2.2), suggesting that the magma source might have been the metasomatized lithospheric mantle wedge subsequently metasomatized by the melts from asthenospheric mantle. Such volcanic rocks are named Nima Group volcanic rocks in this study. The temporal-spatial distribution of Mesozoic-Paleogene volcanic rocks of the Lhasa Block implies that Gangdise Arc volcanic rocks have undergone two times of spatial migration. One is the northward migration, i.e., from Yeba Formation (193～174 Ma) and Sangri Group (J3—K1) in the southernmost area through Zenong Group/Duoni Formation in the north (140～110 Ma) to Nima Group in the northernmost area (100～80 Ma). The other is the migration from north (Nima Group volcanic rocks, 100～80 Ma) to south (Linzizong Group volcanic rocks, 70～40 Ma). The temporal-spatial distribution and geochemical characteristics of volcanic rocks reveal the north-dipping subduction history of the Neo-Tethys oceanic lithosphere, i.e., the evolution from low-angle and north-dipping subduction in the early stage through high-angle roll-back to final detachment.

Abstract:The Pangushan tungsten deposit is an important large-size quartz-vein type W-polymetallic deposit in southern Jiangxi Province. Based on detailed petrographic observations and using the means of Fluid Inclusion Assemblage (FIA), the authors carried out microthermometric and Raman microspectroscopic studies of fluid inclusions in early bismuthinite-wolframite-quartz veins and late (bismuthinite)-wolframite-quartz veins of the main ore-forming stage of the Pangushan tungsten deposit. The fluid inclusions are mainly of H2O-NaCl type and H2O-NaCl-CO2 type together with minor pure CO2 type. The existence of abundant CO2-rich inclusions is a typical feature of the Pangushan Tungsten deposit. Experimental results show that the main homogenization temperature range of the two-phase H2O-NaCl type fluid inclusions is comparable to that of the H2O-NaCl-CO2 type inclusions, while the salinity of the two-phase H2O-NaCl type is higher than that of the H2O-NaCl-CO2 type. In addition, the H2O-NaCl type fluid inclusions show evident decrease in homogenization temperature from the early veins to the late veins at constant salinity. Moreover, less H2O-NaCl-CO2 type inclusions occur in the (bismuthinite)- wolframite-quartz veins while relatively abundant CO2 type inclusions are existent. Raman microspectroscopic studies of various types of inclusions show that, besides water and CO2, the fluid inclusions also contain small amounts of CH4 and N2. The characteristics of fluid inclusions in the Pangushan Tungsten deposit indicate that the fluid immiscibility caused by CO2 escaping possibly led to tungsten precipitation.

Abstract:The Xiaomiaoshan gold deposit in Dingyuan County of Anhui Province is a typical quartz vein type gold deposit in the central southern part of Zhangbaling uplift adjacent to the Tan-Lu fault belt in the west. Gold mineralization mainly occurs in NNE-extending quartz veins in the peripheral contact zone of Guandian-Wawuliu adamellite and subordinately exists as sparse disseminations in altered rocks. Petrographic studies reveal four types of primary fluid inclusions in quartz veins sampled from the Xiaomiaoshan gold deposit, i.e., vapor-rich, liquid-rich, CO2-bearing and daughter minerals-bearing fluid inclusions. Fluid and stable isotopic geochemical methods, such as microthermometry, laser Raman microprobe, bulk composition and H-O isotopic analysis of fluid inclusions, were used to investigate physicochemical properties, chemical composition and sources of the ore-forming fluids so as to probe into the metallogenic mechanism of this type of ore deposits. The homogenization temperatures of these fluid inclusions range from 133℃ to 378℃, with the peak values being in the ranges of 180℃～200℃ and 220℃～260℃. The calculated salinities［w (NaCl)］ range from 0.2% to 44.6% with the peak values between 3% and 6%. Four types of fluid inclusions coexist in the sample; the vapor-rich fluid was homogenized to a single vapor phase, while at the similar temperature range, the liquid-rich fluid was homogenized to a single liquid phase. These phenomena indicate that the boiling process might have played an important role at the ore-forming stage. According to homogenization temperatures, salinities and vapor-liquid ratios, the fluid pressures were estimated to be 4 to 13 GPa, 23 and 60 GPa, respectively, suggesting that gold mineralization took place over 6.5 km in depth. Based on the laser Raman analysis of the fluid inclusions, it is found that the gas composition is mainly CO2, H2O vapor with a tiny amount of CH4. Group analyses of fluid inclusions indicate that the liquid phase mainly contains Na+, K+, Ca2+, F-, Cl-, NO3- and SO42-, while the gaseous phase consists of CO2, N2, H2O, CH4, C2H2 and C2H6. The K+/Na+ ratios vary between 1.55 and 2.75, and F-/Cl- ratios are between 0.02 and 0.03. δ18OH2O values of the fluids trapped in the quartz vein range from -2.39‰ to 2.14‰, and δDH2O from -512‰ to -45.9‰, respectively. The isotopic characteristics indicate that the ore-forming fluids were mostly derived from the magma and mixed with the meteoric water at the late stage. Through integrating geological settings with physiochemical properties and isotopic geochemistry of the ore-forming fluids in the Xiaomiaoshan gold deposit, it is concluded that the NS-trending faults constituted themigration pathways of the ore-forming fluids and places of gold precipitation. When the fluids of high temperature and high salinity were mixed with meteoric water along the fracture zone, the oxygen fugacity increased and the temperature, salinity and pressure decreased remarkably, which caused the disassociation of the gold complexes and resulted in gold precipitation.

Abstract:The microbial oxidation of sulfide minerals in wet metallurgy has been widely studied. In recent years, the reaction between the bacterium Acidithiobacillus ferrooxidans (A.f.) and pyrite in mining environments has also aroused attention and become a focus in the study of reactions between microorganisms and minerals. In this paper, a strain of A.f. isolated from the acid mine drainage (AMD) and the mineral pyrite from the tailings of the Dabaoshan Mine were used to probe into the bio-oxidation of pyrite. Experiments were designed to compare the differences between abiotic oxidation and bio-oxidation of pyrite under different pH conditions and to investigate the effects of A.f. and pH conditions on the oxidation of pyrite.Before the experiment, the pyrite was crushed to less than 0.18 mm in size, immersed in an absolute ethyl alcohol for 30 minutes, and then washed with deionized water 3 times and put in a 50℃ vacuum drying oven for 2 hours for experimental uses. A small amount of the prepared pyrite powder was used to observe its surface morphology under a cold field emission scanning electron microscope. All the immersing experiments were then carried out in 250 mL conical flasks at a cleaning work station. A density of 3% of pulp (3 g of pyrite powder in a 100 mL solution) was added to each flask. The pyrite powder was added to a 9 K culture medium without Fe2+, inoculated with 10% (the ratio between the volume of bacterial suspension added in and that of the total solution) of A.f. suspension, and adjusted to pH 2.00 and 3.00 respectively by using 1:1 H2SO4. The experimental flasks were put in an oscillator for shaking cultures at a constant temperature of 30℃ and a rotating speed of 150 r/min, oscillating 20 hours a day. Experiments without adding A.f. suspension were also conducted at the same time for comparison.The concentrations of cations such as Fe2+, As5+ and Cd2+, anion SO42- and pH values during the experiments were measured regularly. Some of the solid experimental results were collected and dried in a 50℃ vacuum drying oven and then analyzed with XRD. A small quantity of the collected solid result was washed with deionized water 3 times, dried in a 50℃ vacuum drying oven and then investigated under a cold field emission scanning electron microscope.The experimental results showed that Fe2+, Cd2+, As5+ ions were produced by the oxidation of pyrite and that the pyrite is easier to be oxidized at pH 2 than at pH 3. The bacterium A.f. promoted the oxidation of pyrite by raising the apparent oxidation rate by 2～3 times in 30 days of the experiment. The bio-oxidations of pyrite may include indirect oxidation and contact oxidation. The results will provide valuable reference for source remediation of the AMD pollution in the Dabaoshan Mine.

Abstract:Phenol is a kind of hardly degradable organic pollutants which widely exist in wastewater and pose great harm to human environment, so the decontamination of phenol is an urgent task in China. In this paper, photocatalytic degradation of phenol was investigated using natural rutile TiO2 powders from Shanxi Province under irradiation of UV and sunlight. The effects of irradiation time, pH value, initial concentration of phenol and dosage of H2O2 on the efficiency of photocatalytic degradation of phenol were studied. The results indicate that natural rutile TiO2, which is commonly thought to have very low catalytic activity, can effectively photodegrade the phenol when it is synergized with H2O2, but the coexistence of light source, charge-trapping agent and photocatalyst is the precondition of photocatalytic reaction. The degradation efficiency of phenol is much higher in acidic condition than in neutral or alkaline conditions, especially when the pH value is 3.5. When the initial concentration is lower, the phenol can be degraded more completely. When the initial concentration is 60mg/L, the degradation rate is up to 1.922 mg/(L·h). As an effective charge-trapping agent, H2O2 can inhibit the recombination of electron-hole and facilitate the degradation process, and its favorable dosage is 2 ml/L. It is shown that 87.68% of phenol is degraded under sunlight irradiation by natural rutile in 7 h, which iscomparable with the P25 (99.72%), and phenol can be completely degraded by natural rutile TiO2 in 14h.The result of nitrogen adsorption shows that the Brunauer-Emmett-Teller (BET) specific surface area of rutile is only 0.4696 m2/g,which is by far smaller than that of P25 (44 m2/g). According to EPMA and XRD analysis, it is held that the impurity atoms, such as V and Fe, might induce some response to visible light and greatly enhance the photocatalytic capability of natural rutile. As the most common existing form of TiO2 in nature, rutile can be utilized as photocatalyst to tackle the problem of organic pollution. Compared with synthetic titanium dioxide, it can overcome the shortage of low utilization of solar energy and hence has promising environmental application.

Abstract:H-O, C, S, N stable isotope systems are widely used to trace the sources of ore-forming fluids; nevertheless, with the steady accumulation of isotope-related data, the complexity and uncertainty of fluid tracing have become more and more distinct. First, stable isotopic compositions usually overlap various potential source reservoirs and thus result in uncertainty and multi-interpretation. Second, once leaving their sources, ore fluids might experience complex geological processes till ore precipitation. During these processes, various isotopic exchanges and fractionations occur, which dramatically change isotopic compositions of fluids. In addition, diverse post-mineralization alterations further complicate isotopic features of ores. Consequently, the isotopic data from ores should be interpreted very cautiously, especially when used to trace potential sources of ore-forming fluids. With examples of well-researched orogenic lode gold deposits, this paper points out that the interpretation of complex stable isotope data depends not only on potential source reservoirs but also on complicated ore-forming processes, which include isotope exchange during fluid-rock interaction along the pathways traveled by the auriferous fluid, isotopic fractionation at the depositional site, and possible post-ore resetting.Intense sulfur isotope fractionation can be easily driven by oxidation which generally occurs during fluid-rock interaction, phase separation due to fluid pressure fluctuation, and fluid mixing. Therefore, considerable variation of mean δ34S values can occur in quartz veins in different orientations in the same deposits, and even among sulfide crystals of the same stage in the same hand specimen. Wall-rock interaction, immiscibility of CH4 and CO2, and evolution of ore fluids inevitably result in very diverse carbon isotope data of hydrothermal carbonates (especially calcites), which overlap several potential source reservoirs. H-O isotopic data also vary significantly due to the exchange with wall rocks. δD data, commonly obtained from bulk fluid inclusion analysis or calculation according to hydrous mineral analysis using appropriate mineral-water fractionation equation, generally signifies involvement of meteoric water and post-ore resetting because of the failure to eliminate secondary fluid inclusions. In addition, N stable isotope compositions, recorded in N-bearing minerals, e.g., K-feldspar and mica, commonly overlap a variety of potential source reservoirs, particularly metamorphic and magmatic ones. It is therefore very difficult to constrain ore_forming fluid sources by means of stable isotope studies without a serious consideration of the influence of ore-forming processes. However, intensive isotopic researches based on spatial and temporal variation may unveil not only the evolution of ore-forming fluids but also their sources.