东秦岭南泥湖钼铅锌银多金属矿田地球物理场特征与深部找矿预测   总被引：1，自引：0，他引：1       下载免费PDF全文

王耀升  刘申芬  王俊鹤  秦学业  刘国庆  崔小玲 《中国地质》2018,45(4):803-818

南泥湖钼多金属矿田是中国重要的钼(钨)铅锌银多金属矿产地,已探明超大型钼(钨)矿床3处,大型钼(钨)矿床3处,中、大型铅锌银(金)矿床10余处。矿田具有优越的地质成矿条件,深部找矿潜力巨大。现有矿产勘查深度主要是500 m以浅范围,深部(500~2000 m)找矿工作基本为空白,需要使用综合地球物理方法研究深部成矿规律,预测新的矿产资源。文章通过研究该区地质、地球物理场特征和典型矿床物探异常特征,取得了有意义的研究成果。(1)确定了与成矿关系密切的隐伏岩体侵入模型:将全区隐伏岩体从南至北分为3个区,Ⅰ区隐伏岩体顶面深度0~800 m,分布面积约125 km~2;Ⅱ区隐伏岩体顶面深度0.8~1.5 km,分布面积约158 km~2;Ⅲ区隐伏岩体顶面深度1.5~3 km,分布面积约233 km~2。(2)建立了立体成矿模型(根据成矿空间位置的不同从地表向下分为4个空间成矿区)和综合地球物理找矿模型(包括隐伏岩体、隐伏岩体顶上带、岩钟和斑岩体、矿体和矿化体的地球物理场标志)。(3)指出隐伏岩体顶上带及其上方的岩钟、岩脉、岩枝和小斑岩体等是成矿有利部位。(4)预测了找矿潜力;总结了寻找钼钨铅锌银金矿产的勘查方法技术组合。研究成果对在该区和类似矿区进行深部找矿工作具有重要意义。  相似文献   

Gold dispersion in tropical weathering profiles at the Belikombone gold anomaly (Bétaré Oya gold district), east Cameroon     

《Chemie der Erde / Geochemistry》2021,81(4):125770

The distribution of gold in the weathering blanket at the Belikombone gold prospect in east Cameroon provides insights into gold mobility in the secondary environment and in tropical terrains worldwide. Both gridline-controlled sampling of topsoil (surface samples) and sampling of various layers in pits are used and the gold assay for each sample determined by NiS fire assay with ICP-AES finish. One hundred and thirty-two (132) surface samples and a total of 206 samples from 19 exploration pits were analyzed. The results from the topsoil samples show an anomaly with the highest Au concentration at 5.9 mgkg⁻¹. The mineralization corridor follows a NE-SW trend. The horizons within the pits range from sap rock at the base, through saprolite, rubble layer rich in relict quartz material to a ferruginous loose layer at the top although some horizons are missing in some pits. All the layers contain gold and the highest concentration in the sap rock horizon is 3.4 mgkg⁻¹ while the rubble layer has a gold high of 6.1 mgkg⁻¹. The individual soil horizons show no systematic gold trends and given the presence of gold in all layers, the patterns point towards supergene dissolution and redistribution of gold. Gold enrichment within the upper horizons in the weathering blanket is attributed to sequestration by Fe oxides of chemically remobilized gold. However, the high gold content within the sap rock and saprolite layers suggests that migration of gold in the particulate form supersedes chemical gold redistribution. Particulate gold obtained by panning samples from the pits varies in shape from euhedral, elongated to irregular. Electron microprobe analysis on the grains record high contents of gold in the rim zones (90.0 to 99.8 wt%). The cores are relatively rich in Ag (12.6 to 14.2 wt%) while the rims are poor in Ag. The low Ag content in the rims is attributed to the preferential leaching of Ag. The soil pH value in this area varies between 3.6 and 7.3. Under such acidic to near neutral conditions, bisulfide and thiosulfate ions can dissolve and transport Au and Ag to be precipitated under surficial conditions creating authigenic Au haloes especially in the saprolite and sap rock layers. Such pH values together with oxidizing Eh conditions explain the solubility of gold in the area. These results are important for geochemical exploration of gold in tropical terrains, and confirm previous studies.  相似文献   

Experimental modeling of Au and Pt coupled transport by chloride hydrothermal fluids at 350–450°C and 500–1000 bar     

A. V. Zotov  B. R. Tagirov  L. A. Koroleva  V. A. Volchenkova 《Geology of Ore Deposits》2017,59(5):421-429

The coupled solubility of Au_(cr) and Pt_(cr) has been measured in acidic chloride solutions at 350–450°С and 0.5 and 1 kb using the autoclave technique with determination of dissolved metal contents after quenching. The constants of the reaction combining the dominant species of Au and Pt in high-temperature hydrothermal fluids (K_(Au–Pt)) have been determined: 2 Au_(cr) + PtCl₄^2- = Pt_(cr) + 2AuCl₂^-; log K_(Au–Pt) =–1.02 ± 0.25 (450°С, 1 kb), 0.09 ± 0.15 (450°С, 0.5 kb), and –1.31 ± 0.20 (350°С, 1 kb). It has been established that the factors affecting the Au/Pt concentration ratio in hydrothermal fluids and precipitated ores are temperature, pressure, redox potential, and sulfur fugacity. An increase in temperature results in an increase in the Au/Pt concentration ratio (up to ~550°С at P = 1 kb). A decrease in pressure and redox potential leads to enrichment of fluid in Au. An increase in sulfur fugacity in the stability field of Pt sulfides results in increase in the Au/Pt concentration ratio. Native platinum is replaced by sulfide mineral in low-temperature systems enriched in Pt (relative to Au).  相似文献   

Rate controls on the chemical weathering of natural polymineralic material. II. Rate-controlling mechanisms and mineral sources and sinks for element release from four UK mine sites,and implications for comparison of laboratory and field scale weathering studies     

《Applied Geochemistry》2006,21(2):377-403

Predictions of mine-related water pollution are often based on laboratory assays of mine-site material. However, many of the factors that control the rate of element release from a site, such as pH, water–rock ratio, the presence of secondary minerals, particle size, and the relative roles of surface-kinetic and mineral equilibria processes can exhibit considerable variation between small-scale laboratory experiments and large-scale field sites.Monthly monitoring of mine effluent and analysis of natural geological material from four very different mine sites have been used to determine the factors that control the rate of element release and mineral sources and sinks for major elements and for the contaminant metals Zn, Pb, and Cu. The sites are: a coal spoil tip; a limestone-hosted Pb mine, abandoned for the last 200 a; a coal mine; and a slate-hosted Cu mine that was abandoned 150 a ago. Hydrogeological analysis of these sites has been performed to allow field fluxes of elements suitable for comparison with laboratory results to be calculated. Hydrogeological and mineral equilibrium control of element fluxes are common at the field sites, far more so than in laboratory studies. This is attributed to long residence times and low water–rock ratios at the field sites. The high water storativity at many mine sites, and the formation of soluble secondary minerals that can efficiently adsorb metals onto their surfaces provides a large potential source of pollution. This can be released rapidly if conditions change significantly, as in, for example, the case of flooding or disturbance.  相似文献   

应用偏光显微镜和电子探针技术研究安徽铜官山矽卡岩型铜铁矿床伴生元素金银铂钯铀的赋存状态   总被引：4，自引：2，他引：2  

刘亚非  赵慧博  高志文  来志庆 《岩矿测试》2015,34(2):187-193

安徽铜官山矽卡岩型铜铁矿床富含多种稀有贵金属金银铂钯和铀,本文应用偏光显微镜与电子探针技术对该地区贵金属和铀矿物的含量、矿物种类、赋存状态及其嵌布特征进行研究,并利用电子探针Th-U-Pb定年技术推测铀矿物的形成时期。研究表明:金主要以银金矿独立矿物存在,成色均值约为638,与铜的硫化物密切依存,金矿物形成于成矿中晚期的中低温环境;银的独立矿物有银金矿、碲银矿、辉银矿,还与铜铋铅等以类质同象形式结合形成不同种类的矿物组合,且含量在74.15%~0.12%不等;铂钯矿物以含铂碲钯矿为主;铀以晶质铀矿独立矿物存在且与磁铁矿密切依存,晶质铀矿的形成年龄约为124±14 Ma,晚于岩体形成年龄(约139 Ma),早于黄铜矿和含金银铂钯等矿物,而与磁铁矿同在燕山中晚期形成。结合镜下观察,认为铜官山矽卡岩型铜铁矿床主要矿物生成顺序依次是:石榴子石-磁铁矿、晶质铀矿,含金银铂钯矿物,黄铜矿。本研究为贵金属选矿提供了线索,同时利用晶质铀矿的年龄数据界定了伴生贵金属的形成年代。  相似文献   

NK8310螯合树脂分离富集地质样品中痕量金银铂钯及其测定   总被引：14，自引：3，他引：14  

李志强  沈慧君 《岩矿测试》2001,20(2):91-96,99

研究了硫脲螯合树脂（NK8310）分类富集地质样品中痕量Au、Ag、Pt和Pd的实验条件。在φ=10％的王水介质中，[AuCI4]^-、[AgCI2]^-、[PtCI6]^2-和[PdCI4]^2-定量吸附于树脂上并与大量贱金属分离；用5g/L硫脲－0.12mol/L HCI溶液洗脱Au、Ag、Pt和Pd，回收率为97％－104％。用硫镍矿管理样以及国家一级标准物质进行分析验证，分析结果与推荐值及标准值吻合，表明NK8310螯合树脂适用于地质样品中Au、Ag、Pt和Pd的分离富集。  相似文献   

Geochemical behavior of Pt and Pd in coastal marine sediments,southeastern margin of the Japan Sea     

《Applied Geochemistry》1993,8(3):265-271

Eighty-one argillaceous marine sediments collected from the southeastern coastal margin of the Japan Sea were analyzed for Pt and Pd by atomic absorption spectrometry using a graphite furnace atomizer after solvent extraction separation. The average Pt (1.2 ± 0.5 ppb) and Pd(1.6 ± 0.9 ppb) contents are generally similar to those of the published crustal abundances. The Pt or Pd is generally enriched in the fine sediment fraction, and positively correlated with Cu, Pb and water depth. The inverse correlation between the Pt or Pd content and redox potential of the sediment suggests that significant amounts of Pt and Pd are supplied in their dissolved forms, and reduced to their metallic states. It is concluded that the Pt and Pd distributions in the coastal marine sediments are controlled by the geological characteristics of the studied area, grain size and redox potential of sediments, water depths, and dissolved O₂ concentration of sea water.  相似文献   

Analysis of influencing factors of clay particle diffusion in electric double layer北大核心CSCD     

尚飞  杨成松  张莲海  周成林  韩大伟  石亚军 《冰川冻土》2022,44(2):495-505

双电层结构对研究黏土力学特性、冻土水分迁移等具有重要意义。为了探究不同影响因素对黏土颗粒扩散双电层电势分布的影响,借鉴Gouy-Chapman-Stern双电层理论,基于Nernst-Planck方程和Poisson-Boltzmann方程,利用数值软件COMSOL定量分析了温度、浓度、颗粒尺寸、颗粒形状以及溶液相对介电常数对扩散双电层电势分布的影响规律。研究表明：温度对电势分布的影响不明显,但随着温度以及Stern层厚度增加,黏土颗粒表面电势和Stern电势均增加;而随着溶液浓度以及相对介电常数减小,表面电势值增加;在矿物成分、表面电荷密度以及颗粒形状确定的情况下,尺寸对于扩散双电层电势分布的影响不显著;但颗粒的不规则形状对电势分布的影响较为明显,当颗粒形状存在夹角时,夹角处的表面电势远大于其他位置,且夹角越小,夹角处表面电势值越大。  相似文献   

Thermochemical redox equilibria of ZoBell's solution     

Darrell Kirk Nordstrom 《Geochimica et cosmochimica acta》1977,41(12):1835-1841

The redox potential of ZoBell's solution, consisting of $\text{3.33 × 10}{}^{\mathrm{?3}}$ molar K₄Fe(CN)₆, $\text{3.33 × 10}{}^{\mathrm{?3}}$ molar K₃Fe(CN)₆ and 0.10 molar KCl, has been measured by a polished platinum electrode vs a saturated KCl, Ag/AgCl reference electrode. Measurements in the temperature range 8–85°C fit the equation $\text{E(}\text{volts}\text{) = 0.23145 ? 1.5220 × 10}{}^{\mathrm{?3}}\text{(t ? 25) ? 2.2449 × 10}{}^{\mathrm{?6}}\text{(t ? 25)}{}^2$ where $\text{t}$ is in degrees Celsius. Evaluation of literature data was necessary to obtain a reliable value for the Ag/AgCl half-cell reference potential as a function of temperature. Combining the measurements from this study with the literature evaluation of the Ag/AgCl reference potential yields the temperature dependent potential for ZoBell's solution: $\text{E(}\text{volts}\text{) = 0.43028 ? 2.5157 × 10}{}^{\mathrm{?3}}\text{(t ? 25) ? 3.7979 × 10}{}^{\mathrm{?6}}\text{(t ? 25)}{}^2$ relative to the standard hydrogen potential. From these data the enthalpy, entropy, free energy and heat capacity for the ferro-ferricyanide redox couple have been calculated. The temperature equation for the potential of ZoBell's solution may be used for checking potentiometric equipment in the determination of the redox potential of natural waters.  相似文献   

Gas-generation potential of shales in small and medium-sized basins: a case study from the Xuanhua Basin,north China     

J. L. Liu  Z. Li  M. H. Chang  S. Wang  L. Chen 《Australian Journal of Earth Sciences》2020,67(3):411-424

Abstract

Small- and medium-sized basins are widely distributed, and some contain commercial gas reservoirs demonstrating their gas-generation potential. The Xuanhua Basin, which is a small-sized coal-bearing basin in north China, includes a promising target for shale-gas exploration in the Xiahuayuan Formation. In this study, we used this basin as a case study to assess the critical geochemical features for small or medium-sized basins to form commercial gas reservoirs. Total organic carbon (TOC) analysis, Rock-Eval pyrolysis, microscopic observation of macerals, vitrinite reflectance measurement and kerogen stable carbon isotope analysis were performed to characterise the organic geochemistry of the Xiahuayuan shales. The original total organic carbon (TOC_o) content and hydrocarbon-generative potential (S_2o) were reconstructed to further evaluate the gas-generation potential of these shales. In addition, geochemical data of shales from other similar-sized basins with gas discoveries were compared. The results showed that the kerogen from the Xiahuayuan Formation is Type III (gas-prone), and macerals are dominated by vitrinite. TOC values showed a strong heterogeneity in the vertical profiles, with most higher than 1.5?wt%. The measured R_o values ranged from 1.4 to 2.0%. However, thermal maturity was not correlated with the present-day burial depth with higher maturity in the wells closest to the diabase intrusion centre. The remaining generation potential (S₂) averaged 0.91?mg HC/g rock, equal to 1.4?cm³ CH₄/g rock, and the average amount of hydrocarbon generated was 4.33?cm³ CH₄/g rock. In small and medium-sized basins, the TOC content of commercially developed gas shales ranged from 0.5 to 2.5?wt%, organic matter was mainly humic (gas-prone), and the burial depth was generally shallow. Biogenic gas reservoirs for commercial exploitation tend to have larger shale thicknesses (120–800?m) than thermogenic gas reservoirs (60–90?m).

1. The Xiahuayuan Formation is a good gas-source rock with gas-prone kerogen type, relatively high TOC values and moderate thermal maturity.

2. The average amount of hydrocarbon generated from the Xiahuayuan shales is about 4.33?cm³ CH₄/g rock, indicating a potential to form a shale gas reservoir.

3. Owing to the influence of diabase intrusions, the Xiahuayuan shales have entered the dry gas window at relatively shallow-buried depths.

4. Small- and medium-sized basins have the potential to generate commercial gas reservoirs with the generated volume mainly a product of the thickness and maturity of black shales.

  相似文献   

矿物热电效应与火山地震之热电异常     

申俊峰  申旭辉  李胜荣  徐立为  杜柏松  王冬丽  王书豪 《地学前缘》2020,27(5):207-217

地壳物质组成的不均一性及矿物形成物理化学条件的复杂性决定了地壳内广泛存在半导体矿物。半导体矿物的主要特征之一是晶格内存在一定量由成分(本征元素或杂质元素)异化或结构缺陷形成的潜在载流子。当遇有温差热激发条件时,梯度温度场会驱动矿物晶体内的潜在载流子定向移动,进而产生温差热电势,这种现象称作热电效应。一般来说,火山地震孕育和发生过程中其震源处常常存在由扰动热流而产生的不均匀热场,该热场的梯度效应(温差效应)能够触发半导体矿物产生热电效应,并将热能转化成电能。因此推测,作为火山地震的重要前兆之一,地电异常的出现很可能存在热电效应的贡献,即火山地震地电异常存在热电效应机制。这一认识对于深刻理解火山地震孕育过程中的地电异常具有启示意义。  相似文献   

Isotope palaeohydrology and the prediction of long-term repository behaviour     

Jean-Charles Fontes 《地学学报》1994,6(1):20-36

There are considerable, well-recognized difficulties involved in the investigation of very low permeability rocks by conventional measurements of water potentials and spatial distribution of hydrological parameters such as permeability and effective porosity. Therefore, most studies of predictive behaviour are based on models which, when unconstrained by data, are often worse than no model at all. Geochemistry and environmental isotope geochemistry are techniques well suited for hydrological investigations of potential sites of nuclear waste isolation and for constraining predictive models. Stable isotopes constitutive of the water molecule (²H and ¹⁸O) may give information on the origin of the water, especially ²H which is practically uninvolved in isotope exchange with rock-forming minerals. Variations in stable isotope contents can be related to palaeohydrological and palaeoclimatic conditions whereas ³H is indicative of recent recharge. The ¹³C content of dissolved carbon is related to its origin(s) and the ¹⁴C activity gives a time-scale. However, the initial carbon isotope contents can be modified by various diagenetic effects such as precipitation/dissolution of secondary calcite and oxidation of reduced carbon. The heavy isotope content of the Total Dissolved Inorganic Carbon (TDIC) cannot be interpreted without a detailed knowledge of the carbon chemistry and of the mineralogy and isotope contents of secondary carbonates. Species of Dissolved Organic Carbon (DOC), with high molecular weights (HMW) can generally be attributed to soil derived compounds. Their ¹⁴C content may be measured by AMS (Accelerator Mass Spectrometry) thus providing an estimate of the time elapsed since recharge took place. Chlorine-36 is an interesting potential tool for dating old ground waters because of its long half-life (301 kyr) and its hydrophilic behaviour. It can be also produced in situ in significant amount if the rocks are rich (some tens of ppm) in U and Th. In such cases, this time dependent build-up provides a more systematic radiochronometer of CI^- residence time in the rock than the decay of cosmic input ³⁶CI, provided no Cl^- is leached from the rock. The isotopic composition of aqueous sulphur compounds depends on their origin and on their diagenetic evolution. The redox reactions of SO^2-₄ reduction or of S^2- oxidation are marked by strong isotope effects especially when generated by bacteria. Sulphate reduction by organic matter is a potential source of dissolved inorganic carbon and may thus interfere with ¹⁴C age interpretations. After discussion of the possible age and origin of waters and solutes, some scenarios of evolution of local and regional palaeohydrological conditions are proposed. Examples are given with special emphasis on detailed results from the Fennoscanian shield (Stripa project), and from northern Switzerland.  相似文献   

Reductive deposition of graphite at lithological margins in East Central Vermont: a Sr, C and O isotope study   总被引：3，自引：0，他引：3  

K. A. Evans  M. J. Bickle  A. D. L. Skelton  M. Hall  H. Chapman 《Journal of Metamorphic Geology》2002,20(8):781-798

O, Sr and C isotopes from east‐central Vermont are used to provide information on the timing and volume of metamorphic fluid flow. The results are then used to assess the evidence for redox transformations between C species. Oxygen profiles are homogenised on a metre scale; comparison with Sr isotopes suggest that O alteration may have occurred over a significantly larger timescale than that of Sr, possibly because O was modified during dewatering and diagenesis in addition to the high temperature alteration recorded by strontium. Sr isotope distributions are consistent with cross‐layer fluid fluxes of 10⁴?10⁶ moles m^?2; absolute values depend on the Sr fluid‐rock distribution coefficient which is poorly known; however, reaction progress constraints suggest that fluxes were towards the lower end of this range. High δ¹³C values observed at lithological boundaries cannot be explained by volume loss or closed system processes and are taken to indicate reductive precipitation of graphite as a result of mixing between CO₂ and CH₄‐bearing fluids. Mass balance calculations indicate that redox reactions occurring under metamorphic conditions convert a minimum of 10% of the CO₂ released from limestones into graphite, thus providing a potentially important control on the average residence time of C within the crust with implications for C cycling models.  相似文献   

High levels of uranium and radium in groundwaters at Canada's Underground Research Laboratory, Lac du Bonnet, Manitoba, Canada     

M. Gascoyne 《Applied Geochemistry》1989,4(6)

High concentrations of U and²²⁶Ra, and elevated²³⁴U/²³⁸U activity ratios have been measured in groundwater samples collected from water supply wells and exploratory boreholes in the area surrounding the Underground Research Laboratory (URL) of Atomic Energy of Canada Limited, in southeastern Manitoba. All groundwaters come from the Lac du Bonnet granite batholith or sediments overlying the batholith.Uranium concentrations attain almost 1 mg/l in some shallow, low-salinity groundwaters, whereas²²⁶Ra tends to be high (up to 38 Bq/l) in deeper, saline waters. The U concentrations are some of the highest observed in global groundwaters, yet no significant ore body or mineralization is known in the area. Analyses of unaltered rock samples of the Lac du Bonnet granite show slight U enrichment over average Canadian Shield granites (6.5 μg/g vs 4 μg/g), and altered wall rock in fracture zones is enriched in U by up to an order of magnitude compared to adjacent bedrock. Low²³⁴U/²³⁸U activity ratios in this altered rock indicate active and recent leaching of U by groundwater.The key control on U concentration appears to be redox potential. Concentrations of U in rock, residence time and groundwater composition are of lesser importance. Geochemical modelling of the shallower, oxidized waters indicates that U speciation consists mainly of anionic carbonate complexes of the uranyl ion. This is supported by the remarkable efficiency of an anionic filter developed to remove high levels of U from drinking water in the area.In more reducing groundwaters, U concentrations are similar to those determined in recent experimental work on uraninite solubility in the pH range 7–8.5. Colloidal U is <10% of total U and organic complexation is unlikely to be significant because of low dissolved organic concentrations. The results emphasize the significance of redox potential in controlling U mobility in both oxidizing and reducing environments and indicate the usefulness of U concentration in estimating groundwater Eh.  相似文献   

湘西北黑色岩系中的镍钼矿床及其贵金属矿化特征   总被引：3，自引：0，他引：3       下载免费PDF全文

游先军  戴塔根  罗卫  彭学勤  鲍振襄  包觉敏 《地质找矿论丛》2009,24(1):15-22

湖南西北部下寒武统黑色岩系蕴藏着丰富的镍钼钒多金属矿床及其伴生的Au,Ag,Pt,Pd等贵金属矿化。它是我国新类型的镍钼矿床及贵金属矿化极具找矿潜力的地区。富含有机质和黄铁矿的黑色岩系既是镍钼矿的富集层,也是贵金属矿化的主要富集层。矿床的成矿作用是伴随热水的加入而开始,热水沉积与正常沉积交替期是成矿的高峰期,至正常沉积期结束。生物及生物地球化学作用在黑色岩系的成岩成矿过程中起了重要作用。矿床以同生沉积为主,兼有热水性质沉积特点。其成因应归属于生物地球化学沉积矿床范畴。  相似文献   

Mineralogy, geochemistry and stratigraphy of the Maslovsky Pt–Cu–Ni sulfide deposit, Noril’sk Region, Russia     

Nadezhda Alexandrovna Krivolutskaya  Alexandr Vladimirovich Sobolev  Sergey Grigor’evich Snisar  Bronislav Iosiphovich Gongalskiy  Dmitry Vladimirovich Kuzmin  Folkmar Hauff  Irina Nikolaevna Tushentsova  Natalya Mikhailovna Svirskaya  Natalya Nikolaevna Kononkova  Tatyana B. Schlychkova 《Mineralium Deposita》2012,47(1-2):69-88

We report new data on the stratigraphy, mineralogy and geochemistry of the rocks and ores of the Maslovsky Pt–Cu–Ni sulfide deposit which is thought to be the southwestern extension of the Noril’sk 1 intrusion. Variations in the Ta/Nb ratio of the gabbro-dolerites hosting the sulfide mineralization and the compositions of their pyroxene and olivine indicate that these rocks were produced by two discrete magmatic pulses, which gave rise to the Northern and Southern Maslovsky intrusions that together host the Maslovsky deposit. The Northern intrusion is located inside the Tungusska sandstones and basalt of the Ivakinsky Formation. The Southern intrusion cuts through all of the lower units of the Siberian Trap tuff-lavas, including the Lower Nadezhdinsky Formation; demonstrating that the ore-bearing intrusions of the Noril’sk Complex post-date that unit. Rocks in both intrusions have low TiO₂ and elevated MgO contents (average mean TiO₂ <1 and MgO?=?12?wt.%) that are more primitive than the lavas of the Upper Formations of the Siberian Traps which suggests that the ore-bearing intrusions result from a separate magmatic event. Unusually high concentrations of both HREE (Dy+Yb+Er+Lu) and Y (up to 1.2 and 2.1?ppm, respectively) occur in olivines (Fo_79.5 and 0.25% NiO) from picritic and taxitic gabbro-dolerites with disseminated sulfide mineralization. Thus accumulation of HREE, Y and Ni in the melts is correlated with the mineral potential of the intrusions. The TiO₂ concentration in pyroxene has a strong negative correlation with the Mg# of both host mineral and Mg# of host rock. Sulfides from the Northern Maslovsky intrusion are predominantly chalcopyrite–pyrrhotite–pentlandite with subordinate and minor amounts of cubanite, bornite and millerite and a diverse assemblage of rare precious metal minerals including native metals (Au, Ag and Pd), Sn–Pd–Pt–Bi–Pb compounds and Fe–Pt alloys. Sulfides from the Southern Maslovsky intrusion have δ ³⁴S?=?5–6‰ up to 10.8‰ in two samples whereas the country rock basalt have δ ³⁴S?=?3–4‰, implying there was no in situ assimilation of surrounding rocks by magmas.  相似文献   

Highly siderophile element behaviour accompanying subduction of oceanic crust: Whole rock and mineral-scale insights from a high-pressure terrain   总被引：1，自引：0，他引：1  

C.W. Dale  K.W. Burton  D.G. Pearson  O. Alard  T.W. Argles 《Geochimica et cosmochimica acta》2009,73(5):1394-1416

Highly siderophile element concentrations (HSE: Re and platinum-group elements (PGE)) are presented for gabbros, gabbroic eclogites and basaltic eclogites from the high-pressure Zermatt-Saas ophiolite terrain, Switzerland. Rhenium and PGE (Os, Ir, Ru, Rh, Pt, Pd) abundances in gabbro- and eclogite-hosted sulphides, and Re-Os isotopes and elemental concentrations in silicate phases are also reported. This work, therefore, provides whole rock and mineral-scale insights into the PGE budget of gabbroic oceanic crust and the effects of subduction metamorphism on gabbroic and basaltic crust.Chondrite-normalised PGE patterns for the gabbros are similar to published mid-ocean ridge basalts (MORB), but show less inter-element fractionation. Mean Pt and Pd contents of 360 and 530 pg/g, respectively, are broadly comparable to MORB, but gabbros have somewhat higher abundances of Os, Ir and Ru (mean: 64, 57 and 108 pg/g). Transformation to eclogite has not significantly changed the concentrations of the PGE, except Pd which is severely depleted in gabbroic eclogites relative to gabbros (∼75% loss). In contrast, basaltic eclogites display significant depletion of Pt (?60%), Pd (>85%) and Re (50-60%) compared with published MORB, while Os, Ir and Ru abundances are broadly comparable. Thus, these data suggest that only Pt, Pd and Re, and not Os, Ir and Ru, may be significantly fluxed into the mantle wedge from mafic oceanic crust. Re-Os model ages for gabbroic and gabbroic eclogite minerals are close to age estimates for igneous crystallisation and high-pressure metamorphism, respectively, hence the HSE budgets can be related to both igneous and metamorphic behaviour. The gabbroic budget of Os, Ir, Ru and Pd (but not Pt) is dominated by sulphide, which typically hosts >90% of the Os, whereas silicates account for most of the Re (with up to 75% in plagioclase alone). Sulphides in gabbroic eclogites tend to host a smaller proportion of the total Os (10-90%) while silicates are important hosts, probably reflecting Os inheritance from precursor phases. Garnet contains very high Re concentrations and may account for >50% of Re in some samples. The depletion of Pd in gabbroic eclogites appears linked, at least in part, to the loss of Ni-rich sulphide.Both basaltic and gabbroic oceanic crust have elevated Pt/Os ratios, but Pt/Re ratios are not sufficiently high to generate the coupled ¹⁸⁶Os-¹⁸⁷Os enrichments observed in some mantle melts, even without Pt loss from basaltic crust. However, the apparent mobility of Pt and Re in slab fluids provides an alternative mechanism for the generation of Pt- and Re-rich mantle material, recently proposed as a potential source of ¹⁸⁷Os-¹⁸⁶Os enrichment.  相似文献   

北京地区地热水氘过量参数特征分析   总被引：2，自引：2，他引：0       下载免费PDF全文

刘 凯 刘颖超 孙 颖刘久荣  王树芳刘宗明 《中国地质》2015,(6):2029-2029

文章通过80组不同地热田的样品,分析总结了北京地区地热水资源氘过量参数的特征:(1)地热水的平均δ值为5.4,常温地下水的平均d值为6.04,热水的d值与氚值都较低,水岩作用所导致的氧同位素交换比冷水更容易进行;(2)地下热水的氢和氧同位素组成具有明显的热交换趋势,d值随地下水年龄增大而递增,当地热水年龄为(12.76±0.13)ka时,d值为11.2,而当地热水年龄为(38.96±0.63)ka,d值为14.6;(3)在同一地区,d值随着地下水埋深加大而减小,埋深为125.13 m时d值为5.72,埋深为3221 m时,d值为3.03;(4)从补给源到排泄区,地下水的d值应逐渐降低,其中北部补给区平均d值为7.31,北京断陷盆地平均d值为5.68,南部凤河营地区仅为-9.20;补给源区与排泄区水的d的差值越大,地下水的运动速度越慢;(5)当Eh小于200 m V时,北京地区地下热水的d值随着Eh值的降低而减少,如在桐热-7中,氧化还原电位为-326 m V,d值为-9.20,而在TR-43中氧化还原电位为158 m V,d值为7.48;当Eh大于200 m V时,地下热水的d值随着Eh值的降低而增加,但增幅较小。  相似文献   

Sulphate reducing bacteria to precipitate mercury after electrokinetic soil remediation     

T. Håkansson M.Sc.  P. Suer MSc  PhD  B. Mattiasson  B. Allard 《International Journal of Environmental Science and Technology》2008,5(2):267-274

Combined treatment with electroremediation and sulphate reducing bacteria (SRB) was tested in laboratory and pilot scale. The contaminated soil came from a chlor-alkali factory and contained about 100 mg/kg Hg. Iodide/iodine complexing agent was used to mobilize mercury. Mercury iodide complexes were moved to the anode solution using an electric field. The anode solution was then mixed with hydrogen sulphide (H₂S) containing water, causing precipitation of mercury sulphide. The H²S was produced at site by a SRB reactor. Precipitation problems arising from the nature of the anode solution were expected, since this solution is highly acidic, very oxidised and may contain iodide/iodine that strongly complexes mercury and can hinder mercury sulphide precipitation. Mercury concentrations in the anode solution were up to 65.7 mg/L (field) and 15.4 mg/L (lab. scale). Reduction of mercury in the water was >93% at all times. Iodide did not hinder the process: Nonetheless, in the lab system, iodide concentration was high in the anode solution but mercury reduction was> 99.9%. The redox potential was sufficiently low for HgS precipitation during the experiments, except for a short period, when the mercury removal decreased to 94%. Sulphate reducing bacteria are shown as a viable tool for the treatment of mercury contaminated, acidic, oxidative, iodide containing water, such as that produced by electrokinetic remediation. A second SRB step or other water treatment is required to reduce the mercury concentration to environmentally acceptable levels. Redox potential is the most sensitive factor in the system.  相似文献   

湘黔地区下寒武统黑色岩系型镍钼矿床中磷结核的成分特征初步研究          下载免费PDF全文

江永宏 《地质找矿论丛》2010,25(1):12-17

对湘黔地区下寒武统黑色岩系底部镍钼矿床中磷结核的成分进行了电子探针分析。根据20个磷灰石成分的测定结果,得出Ca/P变化范围为1.36~1.710,平均值为1.605,认为磷结核中磷灰石类型为羟磷灰石,成因类型为生物化学沉积型。磷结核中Na+,Fe2+,Al3+,La3+,Sm3+,Ce+,Cr3+,Ti4+的含量较高,并且均显示了异常丰富的组合类型,如Na+和LREE。在1/4大小的磷结核横剖面上,存在着单核或双核沉积中心,结核的内部构造类型为不规则纹层状。磷结核从边部到中心的贵金属元素,其活性元素相对惰性元素的参数(Pd/Pt,Ag/Au,TD/SUHR)呈现同样的变化趋势。磷结核的外层是相对活性的元素,核部则为相对惰性的元素,部分相对活性的元素(如Pt,Pd,Ag)向外层发生初步迁移。铂族元素的超常富集归因于携带海底岩石物质的热水作用。  相似文献