Sulfide saturation mechanism of the Poyi magmatic Cu-Ni sulfide deposit in Beishan,Xinjiang, Northwest China     

《Ore Geology Reviews》2017

The Poyi Cu-Ni deposit is hosted by the Early Permian Pobei mafic-ultramafic complex along the northern margin of the Tarim Plate. This series of multiple intrusions in the Poyi deposit can be divided into four lithologies: gabbro, dunite, hornblende peridotite, and wehrlite. The ore body consists mainly of disseminated sulfides hosted by hornblende peridotite. All the Poyi deposit sulfides show positive Δ³³S values from 0.004 to 0.221‰ and negative δ³⁴S values from −0.8 to −3.5‰. High Ni contents occur in the hornblende peridotites, which exhibit the highest Δ³³S value of 0.221‰ and the lowest δ³⁴S value of −3.5‰, indicating contamination by sulfides from Archean sedimentary rocks. This contamination was important during sulfide saturation in the Poyi intrusions and likely occurred at depth before the emplacement of the Poyi intrusions. The intrusions incorporated country rocks during their emplacement and consolidation, and the degree of assimilation increases from the central lithofacies (i.e., the hornblende peridotite) to the marginal lithofacies (i.e., the wehrlite, dunite, olivine gabbro, and gabbro). Higher Ni contents are correlated with lower degrees of contamination; thus, we infer that the contamination by the country Paleoproterozoic rocks, which contain significant amounts of gneiss and marble, hindered sulfide saturation.The whole-rock Ni content is negatively correlated with the MgO and Fo contents in the olivine and positively correlated with the FeO and MnO contents in the olivine. During crystallization, olivine becomes gradually richer in FeO but poorer in MgO, and Mn tends to be enriched in the late stages of the melt. We infer that the fractional crystallization of olivine was an important factor during sulfide saturation.  相似文献   

Volatile Organic Sulfur Compounds in a Meromictic Alpine Lake     

M. Fritz  R. Bachofen 《洁净——土壤、空气、水》2000,28(4):185-192

The full spectrum of volatile sulfur compounds was detected in the water column of the permanently stratified meromictic Lake Cadagno. Besides hydrogen sulfide it included methanethiol, carbonyl sulfide, dimethyl sulfide, carbon disulfide, and dimethyl disulfide. Their distribution in the water column suggests that these compounds are of biogenic origin. Except for carbon disulfide which is present in all layers of Lake Cadagno, these volatile organic sulfur compounds are restricted to the anoxic part of the lake. For methanethiol, dimethyl sulfide, and carbon disulfide maximum concentrations were observed in the redox transition zone and in the sediment porewater. Carbon disulfide is the most abundant volatile organic sulfur compound with concentrations of up to 60 μmol L^–1. The concentrations of the methylated sulfides are in the nmolar range. Although their concentrations varied during the summer months, seasonal trends of the concentrations of volatile organic sulfur compounds did not follow a consistent pattern. The restriction of most sulfur species to the anoxic layers of the lake indicates that their production originates from anaerobic microbial degradation of biomass and not from its release from a specific precursor like dimethylsulfoniumpropionate as in marine environments.  相似文献   

Seasonal dynamics of microbial sulfate reduction in temperate intertidal surface sediments: controls by temperature and organic matter   总被引：1，自引：0，他引：1  

Abdul M. Al-Raei  Katja Bosselmann  Michael E. Böttcher  Britta Hespenheide  Franz Tauber 《Ocean Dynamics》2009,59(2):351-370

The role of microbial sulfate reduction on organic matter oxidation was studied quantitatively in temperate intertidal surface sediments of the German Wadden Sea (southern North Sea) on a seasonal base in the years 1998–2007. The sampling sites represent the range of sediments found in the back-barrier tidal area of Spiekeroog Island: sands, mixed and muddy flats. The correspondingly different contents in organic matter, metals, and porosities lead to significant differences in the activity of sulfate-reducing bacteria with volumetric sulfate reduction rates (SRR) in the top 15 cm of up to 1.4 μmol cm^?3 day^?1. Depth-integrated areal SRR ranged between 0.9 and 106 mmol m^?2 day^?1, with the highest values found in the mudflat sediments and lower rates measured in sands at the same time, demonstrating the impact of both temperature and organic matter load. According to a modeling approach for a 154-km² large tidal area, about 39, 122, and 285 tons of sulfate are reduced per day, during winter, spring/autumn, and summer, respectively. Hence, the importance of areal benthic organic matter mineralization by microbial sulfate reduction increases during spring/autumn and summer by factors of about 2 and 7, respectively, when compared to winter time. The combined results correspond to an estimated benthic organic carbon mineralization rate via sulfate reduction of 78 g C m^?2 year^?1.  相似文献   

Multi-technique investigation reveals new mineral, chemical, and textural heterogeneity in the Tagish Lake C2 chondrite     

M.R.M. Izawa  R.L. Flemming  P.J.A. McCausland  G. Southam  D.E Moser  I.R. Barker 《Planetary and Space Science》2010,58(10):1347-449

The Tagish Lake meteorite, an ungrouped C2 chondrite that is related to CI and CM chondrites, is a heterogeneous accretionary breccia with several distinct lithologies that, in bulk, are thought to represent the first known sample of a primitive carbonaceous D-type asteroid. Textural and chemical zoning of clasts and matrix have been little studied and promise additional insight into early solar system processes in both the solar nebula and on the Tagish Lake parent asteroid. We have examined an intact 2.9 g fragment and two polished thin sections from the spring 2000 (non-pristine) Tagish Lake collection to ascertain the major mineralogy and textures of notable features such as chondrules, amoeboid olivine aggregates (AOAs), inclusions, clasts, matrix, and fusion crust. We designed three stages of analysis for this friable meteorite: an initial, non-destructive in situ reconnaissance by μXRD to document meteorite mineralogy and textures and to identify features of interest, followed by spatially correlated μXRD, SEM-EDX and colour SEM-CL analysis of polished thin sections to fully understand mineralogy and the record of texture development, and finally higher resolution SEM-BSE mapping to document smaller scale relationships.Our analyses reveal several previously unreported or poorly characterized features: (1) distinctive colour cathodoluminescence (CL) zoning in relict CAI spinel, in chondrule and AOA forsterite, and in calcite nodules occurring throughout the Tagish Lake matrix. Forsterite frequently shows CL colour and intensity zonation that does not correspond with major or minor element differences resolvable with EPMA, indicating a trace element and/or structural CL-activation mechanism for the zonation that is likely of secondary origin; (2) an irregular inclusion dominated by magnesioaluminate spinel, dolomite, and phyllosilicates with traces of a Ca, Ti oxide phase (likely perovskite) interpreted to be a relict CAI; (3) variable preservation of mesostasis glass in porphyritic olivine chondrules. We anticipate that our multi-technique methodology, particularly non-destructive μXRD, can be successfully applied to other rare and friable materials such as the pristine Tagish Lake fragments.  相似文献   

近年平流层气溶胶模式研究综述     

张峰  刘煜  李维亮 《气象科技》2012,40(3):456-465

平流层气溶胶在全球大气的辐射与化学平衡中起着重要作用,对全球气候变化有着重要的影响。数值模拟研究是研究平流层气溶胶浓度、粒径分布及其化学组成的重要手段之一。回顾了平流层气溶胶模式的发展历程,并对现今研究中较有代表性的5种模式进行了比较,着重考察了模拟结果在OCS、SO2分布情况等方面与实测数据的相符程度。结果发现5种模式均可再现平流层气溶胶和它的主要前体气体分布的大部分特征,但同时也都存在各自的局限。最后展望了平流层气溶胶模式未来的发展方向以及需要改进的问题。  相似文献   

东疆天宇岩浆Cu-Ni矿床的铂族元素地球化学特征及其对岩浆演化、硫化物熔离的指示     

唐冬梅 《地质学报》2009,83(5):680-697

新疆东部天宇镁铁-超镁铁杂岩体位于中天山地块的北部边缘,北侧为塔里木板块前缘活动带－沙泉子深大断裂。该杂岩体由辉长岩、辉石岩、橄辉岩、辉橄岩和橄榄岩组成,橄辉岩、辉橄岩和橄榄岩是主要的Cu、Ni矿赋矿岩相。同位素稀释法测得的铂族元素（PGE）结果显示天宇镁铁-超镁铁岩和铜镍矿石中∑PGE含量低（0.106～57.369ppb）,为原始地幔的0.01～1倍。随岩石基性程度的升高,铂族元素含量略有增高。不同矿化程度的矿石大致表现出随硫化物含量的增多,∑PGE含量增高的趋势。岩石和矿石标准化曲线均表现出正斜率,Pt都为负异常或无异常（TY602-29除外）。根据岩浆和硫化物中Ni和S含量计算,得出天宇铜镍硫化物矿床R值为348～3807,该R值范围可以形成铜镍矿床,但无法形成铂族元素矿床。Pd/Ir-Cu/Ni的投图显示原始岩浆主要为高Mg玄武岩。矿石中100％硫化物PGE含量远低于地幔5％部分熔融形成的岩浆（R＝1000时）中PGE含量,与高Mg玄武岩10％的熔融程度不符。通过模拟计算,天宇矿区存在同源但R值不同的两批岩浆。  相似文献   

Reduced sulfur and iron species in anoxic water column of meromictic crater Lake Pavin (Massif Central, France)     

Elvira Bura-Naki&#x;  Eric Viollier  Didier Jzquel  Alassane Thiam  Irena Ciglene ki 《Chemical Geology》2009,266(3-4):320-326

The vertical distribution of reduced sulfur species (RSS including H₂S/HS⁻, S⁰, electroactive FeS) and dissolved Fe(II) was studied in the anoxic water column of meromictic Lake Pavin. Sulfide concentrations were determined by two different analytical techniques, i.e. spectophotometry (methylene blue technique) and voltammetry (HMDE electrode). Total sulfide concentrations determined with methylene blue method (∑H₂S_MBRS) were in the range from 0.6 µM to 16.7 µM and were substantially higher than total reduced sulfur species (RSS_V) concentrations determined by voltammetry, which ranged from 0.1 to 5.6 μM. The observed difference in the sulfide concentrations between the two methods can be assigned to the presence of FeS colloidal species.Dissolved Fe was high (> 1000 µM), whereas dissolved Mn was only 25 µM, in the anoxic water column. This indicates that Fe is the dominant metal involved in sulfur redox cycling and precipitation. Consequently, in the anoxic deep layer of Lake Pavin, “free” sulfide, H₂S/HS⁻, was low; and about 80% of total sulfide detected was in the electroactive FeS colloidal form. IAP calculations showed that the Lake Pavin water column is saturated with respect to FeS_am phase. The upper part of monimolimnion layer is characterized by higher concentrations of S(0) (up to 3.4 µM) in comparison to the bottom of the lake. This behavior is probably influenced by sulfide oxidation with Fe(III) oxyhydroxide species.  相似文献   

Gold in the Brunswick No. 12 volcanogenic massive sulfide deposit,Bathurst Mining Camp,Canada: Evidence from bulk ore analysis and laser ablation ICP─MS data on sulfide phases     

Sean H. McClenaghan  David R. Lentz  Jillian Martin  Wilfredo G. Diegor 《Mineralium Deposita》2009,44(5):523-557

The 329-Mt Brunswick No. 12 volcanogenic massive sulfide deposit (total resource of 163 Mt at 10.4% Zn, 4.2% Pb, 0.34% Cu, and 115 g/t Ag) is hosted within a Middle Ordovician bimodal volcanic and sedimentary sequence. Massive sulfides are for the most part syngenetic, and the bulk of the sulfide ore occurs as a Zn–Pb-rich banded sulfide facies that forms an intimate relationship with a laterally extensive Algoma-type iron formation and defines the Brunswick Horizon. Zone refining of stratiform sulfides is considered to have resulted in the development of a large replacement-style Cu-rich basal sulfide facies, which is generally confined between the banded sulfide facies and an underlying stringer sulfide zone. Complex polyphase deformation and associated lower- to upper-greenschist facies regional metamorphism is responsible for the present geometry of the deposit. Textural modification has resulted in a general increase in grain size through the development of pyrite and arsenopyrite porphyroblasts, which tend to overprint primary mineral assemblages. Despite the heterogeneous ductile deformation, primary features have locally been preserved, such as fine-grained colloform pyrite and base and precious metal zonation within the Main Zone. Base metal and trace element abundances in massive sulfides from the Brunswick No. 12 deposit indicate two distinct geochemical associations. The basal sulfide facies, characterized by a proximal high-temperature hydrothermal signature (Cu–Co–Bi–Se), contains generally low Au contents averaging 0.39 ppm (n = 34). Conversely, Au is enriched in the banded sulfide facies, averaging 1.1 ppm Au (n = 21), and is associated with an exhalative suite of elements (Zn–Pb–As–Sb–Ag–Sn). Finely laminated sulfide lenses hosted by iron formation at the north end of the Main Zone are further enriched in Au, averaging 1.7 ppm (n = 41) and ranging up to 8.2 ppm. Laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) analyses of pyrite (n = 97) from the north end of the Main Zone average 2.6 ppm Au and range from the detection limit (0.015 ppm) to 21 ppm. Overall, these analyses reveal a distinct Au–Sb–As–Ag–Hg–Mn association within pyrite grains. Gold is strongly enriched in large pseudo-primary masses of pyrite that exhibit relict banding and fine-grained cores; smaller euhedral pyrite porphyroblasts, and euhedral rims of metamorphic origin surrounding the pyrite masses, contain much less Au, Sb, Ag, As, and Sn. Arsenopyrite, occurring chiefly as late porphyroblasts, contains less Au, averaging 1.0 ppm and ranging from the detection limit (0.027 ppm) to 6.9 ppm. Depth profiles for single-spot laser ablation ICP-MS analyses of pyrite and arsenopyrite display uniform values of Au and an absence of discrete microscopic inclusions of Au-bearing minerals, which is consistent with chemically bonded Au in the sulfide structure. The pervasive correlation of Au with Sn in the Zn–Pb-rich banded sulfide facies suggests similar hydrothermal behavior during the waxing stages of deposition on the seafloor. Under high temperature (>350oC) and moderate- to low-pH conditions, Au and Sn in hydrothermal fluids would be transported as chlorocomplexes. An abrupt decrease in temperature and aH₂S, accompanied by an increase in fO₂ and pH during mixing with seawater, would lead to the simultaneous destabilization of both Au and Sn chlorocomplexes. The enrichment of Au in fine-grained laminated sulfides on the periphery of the deposit, accompanied by sporadic occurrences of barite and Fe-poor sphalerite, supports lower hydrothermal fluid temperatures analogous to white smoker activity on the flanks of a large volcanogenic massive sulfide system. In lower temperature (<350oC) and mildly acidic hydrothermal fluids, Au would be transported by thiocomplexes, which exhibit multifunctional (retrograde–prograde) solubility and a capacity to mobilize Au to the outer parts of the sulfide mound. The sluggish nature of this low-temperature venting together with larger variations in ambient fO₂ could lead to a sharp enrichment of Au towards the stratigraphic hanging wall of massive sulfide deposits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Water management for acid mine drainage control at the polymetallic Zn–Pb–(Ag–Bi–Cu) deposit Cerro de Pasco, Peru     

Bernhard Dold  Cheikh Wade  Lluis Fontbot 《Journal of Geochemical Exploration》2009,100(2-3):133

The geochemical and mineralogical study of the Quiulacocha tailings impoundment has shown that the hydrological connection of the three studied mine-waste systems at Cerro de Pasco (Pyrite-rich waste-rock dump Excelsior, old tailings impoundment Quiulacocha, and the active tailings impoundment Ocroyoc) is a critical concern for effective acid mine drainage (AMD) control and mine-waste management. The Quiulacocha tailings covered 114 ha, comprising 79 Mt of tailings, which contained  50 wt.% pyrite, and are located at 4340 m altitude in a tropical puna climate with about 1025 mm/a rainfall and 988 mm/a of evaporation. The tailings were partially overlain by the Excelsior waste-rock dump, which contains about 26,400,000 m³ of waste rocks that cover 94 ha and contained  60 wt.% of pyrite, which origin from a massive pyrite-quartz replacement body. Therefore, these two mine-waste deposits had a direct hydrological connection, resulting in the export of AMD produced at Excelsior towards Quiulacocha. In the Quiulacocha impoundment there are two different types of tailings recognized, that interact with the AMD from Excelsior: 1) Zn–Pb-rich tailings and 2) Cu–As-rich tailings. During the sampling, the Zn–Pb-rich part of Quiulacocha was not producing important excesses of AMD from the oxidation zone, since the pH increased to near neutral values at 1 m depth. The underlying tailings were still able to neutralize the acidity produced in the oxidation zone through sulfide oxidation by the carbonates (mainly dolomite and siderite) contained in the Zn–Pb mineral assemblage. The main source of AMD in this mine-waste system is the Excelsior waste-rock dump. Its acid seepage infiltrates into Quiulacocha forming a Fe–Zn–Pb plume with a pH 5.5–6.1 and containing up to 7440 mg/L Fe, 627 mg/L Zn, and 1.22 mg/L Pb. The plume was detected at 10–13 m depth in the stratigraphy of Quiulacocha tailings. Additionally, the AMD seepage outcropping at the base of the Excelsior waste-rock dump was channeled on the tailings surface into the Quiulacocha pond (pH 2.3), which covered the Cu–As-rich tailings. Infiltration of this Fe(III)-rich AMD increased tailings oxidation in the southwestern part of the impoundment, and subsequently liberated arsenic by enargite oxidation. Additionally, the AMD collected in the Quiulacocha pond was pumped into the active Ocroyoc tailings impoundment, where sulfide oxidation was strongly enhanced by the input of dissolved Fe(III). Therefore, the AMD management and a hydrological separation of the different mine-waste systems could be a first step to prevent further extension of the AMD problem in order to prevent increased sulfide oxidation by Fe(III)-rich solutions.  相似文献   

Gold contents of sulfide minerals in granitoids from southwestern New Brunswick,Canada   总被引：4，自引：0，他引：4  

Xue-Ming?YangEmail author  David?R.?Lentz  Paul?J.?Sylvester 《Mineralium Deposita》2006,41(4):369-386

The abundance of gold and selected trace elements in magmatic sulfide and rock-forming minerals from Silurian–Devonian granitoids in southwestern New Brunswick were quantitatively analyzed by laser-ablation inductively coupled plasma mass-spectrometry. Gold is mainly hosted in sulfide minerals (i.e., chalcopyrite, pyrrhotite, and pyrite), in some cases perhaps as submicron inclusions (nanonuggets). Gold is below detection (<0.02 ppm) in major rock-forming minerals (i.e., plagioclase, K-feldspar, biotite, hornblende, and muscovite) and oxides (i.e., magnetite, and ilmenite). Gold distribution coefficients between sulfide and granitoid melt are calculated empirically as: . This result suggests that gold behavior in the granitoid systems is controlled by the conditions of sulfur saturation during magmatic evolution; the threshold of physiochemical conditions for sulfur saturation in the melts is a key factor affecting gold activity. Gold behaves incompatibly prior to the formation of sulfide liquids or minerals, but it becomes compatible at their appearance. Gold would be enriched in sulfur-undersaturated granitoid magmas during fractionation, partitioning into evolved magmatic fluids and favoring the formation of intrusion-related gold deposits. However, gold becomes depleted in residual melts if these melts become sulfur-saturated during differentiation, leading to gold precipitation in the early sulfide phases of a granitoid suite. Late-stage Cl-bearing magmatic–hydrothermal fluids with low pH and relatively high oxidation state derived from either progressively cooling magmas at depth or convective circulation of meteoric water buffered by reduced carbon-bearing sediments, may scavenge gold from early sulfide minerals. If a significant amount of gold produced in this manner is concentrated in a suitable geological environment (e.g., shear zones or fracture systems), intrusion-related gold deposits may also be generated. Exploration for intrusion-related gold systems should focus on the areas around evolved phases of granitoid suites that remained sulfur-undersaturated. For sulfur-saturated granitoid suites, the less differentiated phase and associated structures are the most prospective targets.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.  相似文献