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1.
Laser ablation of the Fe and Mn oxide coatings on stream sediments has been tested as a means of rapidly introducing this highly sorptive geochemical exploration medium into an inductively coupled plasma emission spectrometer (ICP) for simultaneous multielement analysis.Training data were obtained by selectively leaching coatings on about ten 1-cm diameter pebbles from 50 sites in the Allen drainage system, Southwest England. The Pb, Zn, Fe and Mn concentrations of the resulting leachates were determined by atomic absorption spectrophotometry. This procedure is relatively rapid and economical, but the leachate is suitable only for the determination of a restricted range of elements (mainly heavy metals). The laser-microprobe testing data were obtained by vaporizing approximately 1 μg of coating from one pebble from each sample site with a laser pulse, producing a crater in the coating 150–200 μm in diameter and 30–50 μm deep. The ablation was effected within a cell which the laser beam penetrates via a quartz window and the vaporized material quickly condenses into an aerosol which is carried in a flow of argon passing through the cell to the ICP, for simultaneous determination of up to 36 elements.Training and testing data for the elements determined were normalized by ratioing to Fe or Mn following a preliminary statistical inspection of the data to ascertain predominant correlations. In the Allen drainage basin, where a narrow and impersistent galena vein with subordinate sphalerite occupies a north-south-trending fracture, Pb determinations on coatings correlate well with the Fe content of coatings, while Zn correlates with Mn. The Pb/Fe dispersion patterns produced by the training and testing procedures are essentially similar, as are the Zn/Mn patterns from each of the procedures, demonstrating the potential of the novel laser microprobe technique.Anomalous Pb/Fe and Zn/Mn ratios in pebble coatings occur in the vicinity of the mineralized fracture. These compare favourably in terms of anomaly contrast and length of dispersion trains (especially their extension beyond major confluences) with the Pb and Zn anomalies detected by the more conventional analysis of the minus 200 μm fraction of the stream sediment. The low levels of potential pathfinder elements associated with mineralization do not lend themselves readily to determination in leachates derived from pebble coatings. Laser microprobe data, however, revealed a low-order but punctual As/Fe anomaly in a tributary, where this cuts the mineralized vein.  相似文献   

2.
A field filtration method for the concentration and separation of suspended particulate matter (SPM) from freshwater systems and the subsequent determination of minor, trace and ultra trace elements (As, Ba, Be, Cd, Co, Cr, Cs, Cu, Ga, Hf, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Sn, Sr, Ta, Th, Tl, U, V, W, Zn and Zr) is validated with respect to detection limits, precision and bias. The validation comprises the whole procedure including filtration, sample digestion and instrumental analysis. The method includes two digestion procedures (microwave acid digestion and alkali fusion) in combination with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Total concentrations of these 27 trace and minor elements have been determined in suspended particulate matter (SPM) from lake and river water with low levels of suspended solids (<2 mg L−1 DW), and a wide range of element concentrations. The precision of the method including filtration, digestion and instrumental determination ranges between 8% and 18% RSD for most elements on a dry weight basis. Higher recovery after acid digestion is found for some elements, probably because of volatilization or retention losses in the fusion procedure. Other elements show higher recovery after fusion, which is explained by more efficient decomposition of refractory mineral phases relative to the non-total acid digestion. Non-detectable concentrations of some elements are reported due to small differences between blank filter levels and the amounts of elements present on the filters after sampling. The method limits of detection range between 0.7 ng and 2.65 μg, as estimated from the blank filter samples. These detection limits are 10–550 times higher compared to the corresponding instrumental limits of detection. The accuracy and bias of the overall analytical procedure was assessed from replicate analysis of certified reference materials. A critical evaluation of the instrumental capabilities of the ICP-QMS instrumentation in comparison with a double focusing sector field plasma mass spectrometry technique (ICP-SFMS) is also included. It was found that a modified microwave acid digestion procedure in combination with ICP-SFMS could replace ICP-AES determinations and fusion digestions for most of the investigated elements. Guidelines and limitations for this time- and labour- efficient procedure, offering accurate results for the majority of elements studied are discussed.  相似文献   

3.
X射线荧光光谱微区分析在铅锌矿石鉴定上的应用   总被引：2，自引：1，他引：1  
自然界很多矿物存在类质同象现象,它们在显微镜下特征相似难以区分,对于这类矿物的鉴定,需要借助X射线衍射分析、电子显微镜、电子探针分析和离子探针分析等手段,获取矿物的化学成分和结构,为矿物鉴别提供有用的信息。本文以铅锌矿石中比较典型且易于收集的方铅矿(Pb 86.60%、S 13.40%)和闪锌矿(Zn 67.10%、S 32.90%)为例,借助偏反光显微镜,初步鉴定矿石的矿物特征;再利用X射线荧光光谱仪微区分析功能,对铅锌矿石标本进行定性和定量鉴定,对矿石所表现的各种特征做矿物学解释。实验结果表明,铅锌矿石标本中存在S、Pb、Zn、Cd等异常元素,并对闪锌矿标本中Zn、S、Fe、Cd等异常元素进行分布分析,绘制组分的二维或三维分布图显示各元素分布的异常区域高度一致;在电荷耦合器的实时监控下,对铅锌矿石标本靶区进行定点定量测定,根据所测组分含量,并结合矿物化学成分理论值定名为方铅矿和闪锌矿。本方法测定闪锌矿标本各组分的相对标准偏差(RSD,n=11)均小于4%,测定结果与电子探针测定结果吻合。本方法只要将矿石制成光片,无需喷碳处理,即可对铅锌矿石中主次量元素进行原位微区定性和定量分析,测定速度快且不破坏矿石标本,解决了类质同象矿物(如方铅矿和硒铅矿、闪锌矿和含铁闪锌矿等)在光学显微镜下鉴定困难的问题,提高了铅锌矿石定名的准确性,为岩矿鉴定工作提供一种新的技术手段。  相似文献   

4.
To determine the bulk chemical compositions of chalcopyrite containing starlike sphalerite and sphalerite including dotlike chalcopyrite, specimens from various types of ore deposits in Japan were used for modal and electron microprobe analyses. According to the analytical results, most of the measured zinc contents in chalcopyrite containing starlike sphalerite are less than 0.8 at%, corresponding to the maximum solubility of zinc in chalcopyrite as determined experimentally at 400°C. However, specimens from the Maruyama deposit in the Tsumo mine contain 1.2–1.4 at% Zn, which are within the solubility limit of an intermediate solid solution (ISS) above 400°C. It is therefore concluded that starlike sphalerite in chalcopyrite are exsolution products derived from primary chalcopyrite solid solution and/or zincic ISS. Measured copper contents in sphalerite including dotlike chalcopyrite yield considerably higher values, i.e., 1.5–6.0 at%, which exceed the solubility limits of copper in sphalerite solid solution as determined experimentally. This result suggests that not all the chalcopyrite dots were exsolved from sphalerite, but that most of them are the product of some other mechanisms.  相似文献   

5.
The Eskay Creek, British Columbia, Canada, is a polymetallic, gold- and silver-rich, volcanic-hosted, massive sulfide deposit. The ore in the deposit is divided into subzones distinguished by mineralogy, texture, grade and metallurgical characteristics. This study presents the results of a mineralogical examination of three composite field samples, with emphasis on the chemistry of sphalerite. Sphalerite is associated with variable amounts of Hg-tetrahedrite and cinnabar, and an array of sulfides, sulphosalts and non-opaque minerals. Electron micro probe analyses of sphalerite in the three composite samples reveal wide variations in compositions. The Hg content in sphalerite in the three samples varies between 0.08 and 16.35 wt%, whereas the Fe content ranges from 0.33 to 2.29 wt%. The chemical formula of the sphalerite shows the compositional range (Zn0.89–0.98Hg0.01–0.09.Fe0.005–0.02)S. Sphalerite exhibits an almost perfect substitution of Hg and Zn, as shown by the negative covariance between them. Sphalerite with the highest Hg contents tends to have the lowest Fe concentrations. The highest Hg contents in sphalerite are recorded in the samples with the highest bulk Hg concentrations and with the highest cinnabar contents.

The compositional variations of sphalerite are important because they can be used in mapping ore forming fluids and indicate possible temporal variations. Second, determination of the compositional variation of the sphalerite in the mine has metallurgical implications because the mineral is an important Zn source. The mineralogical data indicate that non-physical processes (e.g. pyrometallurgy) must be used to separate Hg from Zn concentrates, with direct environmental implications, that is, release of metals, such as Hg, into the environment during mining and processing.  相似文献   


6.
As other calcsilicate-hosted ore deposits the Tumurtijn-ovoo Fe–Mn–Zn deposit is subdued to the question how the ore elements took place, whether linked to epigenetic silicification of a limestone host or bound to syngenetic precipitation during the deposition of a calcareous-siliceous sediment. The comparison of high Zn/Cd ratios of ores from Tumurtijn-ovoo ranging from 514 to 724 with those of other ore deposits relates Tumurtijn-ovoo to the group of submarine hydrothermal deposits which got their ore elements from basaltic source rocks by subseafloor leaching. Hence, respecting geological and textural features of the ores, a synsedimentary precipitation of zinc and cadmium in a volcano-sedimentary environment is suggested for Tumurtijn-ovoo. A group of low Zn/Cd ratios (274–297) is correlated with processes of mobilization and redeposition of sphalerite.  相似文献   

7.
Sphalerite (ZnS) is an abundant ore mineral and an important carrier of elements such as Ge, Ga and In used in high‐technology applications. In situ measurements of trace elements in natural sphalerite samples using LA‐ICP‐MS are hampered by a lack of homogenous matrix‐matched sulfide reference materials available for calibration. The preparation of the MUL‐ZnS1 calibration material containing the trace elements V, Cr, Mn, Co, Ni, Cu, Ga, Ge, As, Se, Mo, Ag, Cd, In, Sn, Sb, Tl and Pb besides Zn, Fe and S is reported. Commercially available ZnS, FeS, CdS products were used as the major components, whereas the trace elements were added by doping with single‐element ICP‐MS standard solutions and natural mineral powders. The resulting powder mixture was pressed to pellets and sintered at 400 °C for 100 h using argon as an inert gas. To confirm the homogeneity of major and trace element distributions within the MUL‐ZnS1 calibration material, measurements were performed using EPMA, solution ICP‐MS, ICP‐OES and LA‐ICP‐MS. The results show that MUL‐ZnS‐1 is an appropriate material for calibrating trace element determination in sphalerite using LA‐ICP‐MS.  相似文献   

8.
Several important mineral deposits of Sn, Zn, Cu, Pb, and other metals associated with Devonian sediments and Yanshanian (Cretaceous) granitic rocks are known in the Dachang district (Guangxi). Early genetic hypotheses related the origin of the deposits entirely to the Yanshanian granites. Recently, it was suggested that in Devonian times an earlier syngenetic metal concentration may have occurred, later overprinted by the Yanshanian metallogeny. This contribution is aimed at placing constraints on the physicochemical conditions during the Yanshanian ore formation-remobilization by studying the sulfide chemistry (arsenopyrite, sphalerite, stannite) and fluid inclusion data on the two major deposits in the area, i.e., the polymetallic cassiterite deposit of Changpo and the Zn-Cu skarn deposit of Lamo. Sphalerite and arsenopyrite are quite abundant in both deposits; stannite is minor, but fairly widespread at Changpo, and quite rare at Lamo. They are accompanied by pyrite, pyrrhotite, galena, chalcopyrite, cassiterite, fluorite, and a large variety of other sulfides and sulfosalts. The main compositional data for sphalerite and arsenopyrite are summarized as follows:Changpo: arsenopyrite associated with pyrrhotite 31.4–36.1 at% As; Associated with pyrite 31.9–33.1 at% As; sphalerite associated with pyrrhotite 18.3–22.2 mol% FeS; associated with pyrite 10.6–18.6 mol% FeS.Lamo: arsenopyrite associated with pyrrhotite 32.9–35.3 at% As; associated with pyrite 30.3–31.7 at% As; sphalerite associated with pyrrhotite, 17.2–24.4 mol% FeS; associated with pyrite 4.2–19.6 mol% FeS.Partitioning of Fe and Zn between coexisting sphalerite and stannite from Changpo indicates temperatures of 300°–350°C. For Lamo, the following fluid inclusion data are available: fluorite, salinities of 0–9.5 equiv. wt% NaCl, and homogenization temperatures between 160°C and 250°C; quartz, moderate salinities (0–4.6 equiv. wt% NaCl), and homogenization temperatures of 208°–260°C. Combining the mineralogical evidence with the compositional and fluid inclusion data, it is suggested that the evolution of the environment during the Yanshanian event was characterized by the following parameters: pressure was relatively low (on the order of 1–1.5 kb); temperature may have been as high as 500°C during deposition of the As-richest arsenopyrites, but eventually dropped below 200°–250°C in the latest stages; with an increase in sulfur activity and/or the decrease in temperature pyrrhotite was no longer stable in the latest stages of mineralization.  相似文献   

9.
筲箕湾铅锌矿床位于黔西北铅锌成矿区中部,为该区铅锌矿床中的又一典型代表,其金属资源量（Pb＋Zn）超过20万t。本文利用电感耦合等离子体质谱（ICP-MS）分析了不同类型矿石中原生矿石硫化物（黄铁矿、闪锌矿和方铅矿）中分散元素含量,结果显示除Cd含量较高外,Ga、In、Se、Tl和Re的富集程度均较低。不同分散元素在硫化物中表现出不同的富集规律,表现为Ga含量在闪锌矿中最高,黄铁矿次之,方铅矿最低;方铅矿中Tl含量高于闪锌矿,黄铁矿最低;Cd在闪锌矿中含量最高,方铅矿次之,黄铁矿最低;从黄铁矿→方铅矿→闪锌矿In含量依次升高;Re含量表现出在闪锌矿中最高,黄铁矿次之,方铅矿最低;Se富集程度从黄铁矿→方铅矿→闪锌矿依次升高。Ga、In和Re在不同颜色闪锌矿中富集程度相似,而Se、Cd和Tl则相对富集在棕色闪锌矿中。统计发现闪锌矿中Zn含量与Cd、Ga含量不呈类质同象的负相关特征,而其中的Fe含量与Cd、Ga含量间表现出曲线相关或负相关特征,暗示Cd、Ga可能是通过替代先进入闪锌矿中的Fe而占据其晶格,这可能是一种新的机制。闪锌矿Ga、Cd、In含量及Ga/In、Zn/Cd比值等参数,指示筲箕湾铅锌矿床形成于中-高温条件,其矿床成因类型与沉积-改造型相似。  相似文献   

10.
A detailed chemical study of groundwater was carried out to elucidate the processes controlling the oxidation and dissolution of sulphide minerals at two massive sulphide deposits in the Iberian Pyrite Belt (IPB), i.e. the mined La Zarza deposit and the unmined Masa Valverde deposit. It was found that major-element compositions varied according to the hydrological regime, La Zarza being in a relatively high area with groundwater recharge (and disturbance due to the human factor) and Masa Valverde being in a relatively low area with groundwater discharge. The variations mainly concern pH, Eh, SO4 and Na concentrations. Metal concentrations were determined (a) by ICP-MS after filtration, and (b) in some cases by voltammetric measurement of Cu, Pb, Zn, Cd and Mn using the Voltammetric In situ Profiling (VIP) System, which allows detection of only the mobile fractions of trace elements (i.e., free metal ions and small labile complexes a few nanometers in size). If one compares the results obtained by each of the two methods, it would appear that the groundwater shows significant enhancement of metal solubility through complexing with organic matter and/or adsorption onto colloids and/or small particles. In areas of sulphide oxidation, however, this solubility enhancement decreases according to Cu>Zn>Cd>Pb. Under very low redox conditions, the attained metal concentrations can be several orders of magnitude (up to 108–109 for Cu and 102–103 for Pb) larger than those expected from equilibrium with respect to sulphide minerals as calculated with the EQ3NR geochemical code; Zn concentrations, however, are close to equilibrium with respect to sphalerite. The implication of these results is discussed with respect both to mineral exploration and to environmental issues.  相似文献   

11.
At Segura, granitic pegmatite veins with cassiterite and lepidolite, hydrothermal Sn–W quartz veins and Ba–Pb–Zn quartz veins intruded the Cambrian schist–metagraywacke complex and Hercynian granites. Cassiterite from Sn–W quartz veins is richer in Ti and poorer in Nb and Nb+Ta than cassiterite from granitic pegmatite. Wolframite from Sn–W quartz veins is enriched in ferberite component. The Sn–W quartz veins contain pyrrhotite, arsenopyrite, sphalerite, chalcopyrite, stannite, matildite and schapbachite and the Ba–Pb–Zn quartz veins have cobaltite, pyrite, sphalerite, chalcopyrite, galena and barite, which were analyzed by electron microprobe. The presently abandoned mining area was exploited for Sn, W, Ba and Pb until 1953. Stream sediments and soils have higher concentrations of metals than parent granites and schists. Sn, W, B, As and Cu anomalies found in stream sediments and soils are associated with Sn–W quartz veins, while Ba, Pb and Zn anomalies in stream sediments and soils are related to Ba–Pb–Zn quartz veins. Sn, W, B, As, Cu, Ba, Pb and Zn anomalies in stream sediments and soils are also related to the respective old mining activities, which increased the mobility of trace metals from mineralized veins to soils, stream sediments and waters. Stream sediments and soils are sinks of trace elements, which depend on their contents in mineralized veins and weathering processes, but Sn, W and B depend mainly on a mechanic process. Soils must not be used for agriculture and human residence due to their Sn, B, As and Ba contents. Waters associated with mineralized veins were analyzed by flame atomic absorption spectroscopy (FAAS) and ICP-AES have high As, Fe and Mn and should not be used for human consumption and agriculture activities. The highest As values in waters were all related to Sn–W quartz veins and the highest Fe and Mn values were associated with the Ba–Pb–Zn quartz veins. No significant acid drainage was found associated with the old mine workings.  相似文献   

12.
贵州天桥铅锌矿床分散元素赋存状态及规律   总被引：12，自引：5，他引：7  
利用电子探针(EPMA)、电感耦合等离子质谱(ICP-MS)等分析了天桥铅锌矿床矿石矿物中分散元素的含量、赋存状态及规律,结果表明分散元素在该矿床中含量达到了综合利用评价指标,有的甚至达到了工业品位(如Cd等);这些分散元素可能以类质同象的形式赋存在硫化物矿物中,其规律为Ga、Cd、In等赋存在闪锌矿中,Ge、Tl等赋存在方铅矿中,黄铁矿中分散元素富集低;在不同颜色闪锌矿中,Ga、Cd富集规律表现为浅色闪锌矿>中色闪锌矿>黑色闪锌矿,而Ge、Tl、In、Se富集表现出中色闪锌矿相对高于浅色及黑色闪锌矿;同标本中,不同颜色闪锌矿的Ge、In富集规律在还显示浅色闪锌矿>中色闪锌矿>黑色闪锌矿,而Ga、Tl、Cd、Se富集规律呈现中色闪锌矿相对高于浅色及黑色闪锌矿.Ga/In、Zn/Cd等参数指示出矿床成因类型可能为热液-沉积-改造.  相似文献   

13.
Geochemical stream sediment survey in Winder Valley, Balochistan, Pakistan   总被引：1，自引：0，他引：1  
A pilot scale geochemical survey of sediments from the Winder Stream (SW Pakistan) and its tributaries was carried out. The Winder Stream mainly receives sediment from the southern extensions of the Mor and Pab Ranges in the District of Lasbela (Balochistan). In these two mountain ranges, rocks from Jurassic to Cretaceous age are exposed. Rocks of the Ferozabad Group comprise of carbonates and siliciclastics of Lower–Middle Jurassic age and occupy the dominant part of the Mor Range. These strata host syngenetic and epigenetic Zn–Pb–Ba mineralizations of Stratiform Sediment-Hosted (SSH) and Mississippi Valley Type (MVT) deposits.Quantitative estimates of mobile and immobile elements were made from active stream sediments of the Winder stream and its tributaries. The samples were analyzed for Ag, Zn, Pb, Cu, Ni, Co, V, Mn, Fe and Ba using atomic absorption spectroscopy. The abundance of these elements is discussed in relation to local geological conditions such as bedrock, climate, weathering, mobility and pH of the dispersing waters. A number of Zn anomalies have been distinguished in the study area. Kharrari (Zn, 360 ppm), Sand (Zn, 340 ppm) and Draber (Zn, 210 ppm) are demarcated as new areas for Zn mineralization. The present study also indicates prospects of Ag, Cu and V in the rocks of the Mor Range.Relationships between various elements have been identified from scattergrams and reflect genetic associations. Whereby the positive correlation between Cu–Zn (0.55, n=18) and Cu–Pb (0.63) is related to possible sulphide mineralization.  相似文献   

14.
铅锌矿床地质样品的Ge同位素预处理方法研究   总被引：1，自引：0，他引：1       下载免费PDF全文
目前Ge同位素研究主要局限于地球有机质(煤等)、火成岩及陨石样品,作为Ge重要储库之一的铅锌矿床,其Ge同位素的研究涉及较少。铅锌矿床样品中Ge的化学分离及提纯是Ge同位素研究的基础。本文详细考察了陨石样品中Ge同位素预处理方法(分离和提纯)对铅锌矿石样品的适用性。阴离子条件实验说明,目前普遍采用的离子交换树脂单柱法虽然对铅锌矿样品中Fe、Se等元素的剔除效果理想,但无法有效剔除其中的Zn,当Zn/Ge比值大于3时,样品必须经过阳离子交换树脂柱作进一步处理剔除Zn。通过对闪锌矿标准样品、锌矿石标准样品的条件实验以及实际闪锌矿样品对条件结果的验证显示,当闪锌矿的称样量为0.15 g左右时,仅需将前人对玄武岩等样品Ge同位素处理方法中阴离子树脂洗脱酸(1.4 mol/L硝酸)的用量6 mL调整为10 mL,而阳离子树脂洗脱方法保持不变,此方法即满足闪锌矿样品Ge同位素的化学分离和提纯要求。样品经过本文推荐的阴阳离子交换树脂双柱法处理后,主要干扰元素(Fe、Zn、Se、Ni)及基质元素的剔除率接近100%,Ge的回收率优于99%。而前人对玄武岩等样品的Ge同位素处理方法中,主要干扰元素(Fe、Zn、Se、Ni)及基质元素的剔除效果亦较好,但Ge的回收率仅为97.3%,比本文推荐方法的Ge回收率要差。利用MC-ICP-MS对Ge化学分离和提纯后的富乐铅锌矿床闪锌矿样品的检验结果显示,测试过程中未见同质异位素以及可能的多原子离子影响,样品中Ge同位素符合质量分馏定律,经过调整后的阴阳离子交换树脂双柱法满足闪锌矿样品的Ge同位素测试要求。  相似文献   

15.
The Gümü hane area near Artvin is highly characteristic due to a significant hydrothermal alteration zone genetically associated with a microdiorite stock and its late-stage derivatives in the form of porphyry plugs that intruded into all the pre-Middle Eocene lithologies. The porphyry intrusion is multi-stage, intermediate to felsic in composition, and divided into pre-ore feldspar porphyries and quartz–feldspar porphyries, syn-ore feldspar–amphibole porphyries, and post-ore feldspar porphyries. Sericitic alteration is dominant, but K-silicate alteration is also observed and is characterised mainly by secondary feldspars, biotites, quartz, anhydrite, magnetite and pyrite veinlets. The central part of the alteration and the porphyry system where syn-ore feldspar–amphibole porphyry outcrops coincides with intense quartz stock-working with anomalous but uneconomical Cu and Au values. In this zone, pyrite is ubiquitous and is accompanied by chalcopyrite and lesser sphalerite, sulphosalts, molybdenite, bornite and magnetite. Chemical analyses of surface and drill core samples show that overall Au and Cu values are around 0.5 ppm and 0.3%, respectively, and that they are in the ranges of 1–2 ppm and 0.3–0.4%, respectively, in the densest stock-work zones.Multi-phase intrusion of porphyries into Late Cretaceous limestone also caused replacement fronts along re-crystallised limestone and porphyry contacts. This type of mineralisation is enriched in Mn, Zn, Cu, Au and Ba, and contains on average 4.7% MnO, 3.2% FeO, 3.1% Zn, 0.95% Cu, 0.3% Pb, 200 ppb Au, 900 ppm Bi and 660 ppm Ba, present in Fe- and Mn-oxides, pyrite, chalcopyrite, sphalerite and lesser bornite, sulphosalts and gold. Supergene oxidation is well developed in these zones.Hydrothermal alteration mass change calculations reflect an intimate relationship between the two types of mineralisation. The lithologies near mineralised fronts are highly depleted in MnO and Zn, and the intensity of depletion is reduced away from the contact into the porphyry. The leached elements are added to the re-crystallised limestone block in which MnO and Zn show an 81-fold and 472-fold increase, respectively, over the least altered limestone. Au and Cu are enriched along the contact both in the porphyry and in the limestone, implying that they may have been derived either from other lithologies in the vicinity or the magma itself.  相似文献   

16.
A number of programs have investigated the use of rock geochemistry in the search for volcanogenic massive sulphide deposits in the Canadian Shield. Regional-scale studies have been successful in differentiating productive from nonproductive volcanic cycles. Wall-rock studies have successfully delineated alteration halos related to the mineralizing event. While an alteration halo has been identified around the South Bay massive sulphide deposit, this halo does not extend far enough from the deposit to be useful for reconnaissance purposes. The authors therefore tested the possibility of enhancing detection of a primary trace-element halo by using the heavy mineral fraction of the rocks.The geochemical dispersion of trace elements in the heavy-mineral fraction of rocks was investigated around the South Bay massive sulphide deposit, in the Superior Province of the Canadian Shield. Approximately 270 samples were ground to 74–500 μm (−35 +200 mesh) and separated using the heavy liquid bromoform. Following removal of the magnetic fraction, the samples were further pulverized, and analyzed by atomic absorption spectrophotometry for Cu, Pb, Zn, Ag, Fe, Mn, Co and Ni. Corresponding whole-rock samples were analyzed to provide for a comparative study with the whole-rock geochemistry.Analysis of the heavy-mineral fraction of rocks revealed strong and extensive halos of Cu, Pb, Zn and Ag persisting in some cases up to 10 km along strike away from the South Bay Deposit. By comparison, in the whole-rock data, halos of Pb, Ag and Zn were detected no farther than 1–2 km away from the deposit. Furthermore, trace-element content in the whole rocks appeared to be dominated by rock type; either multivariate statistical techniques, or separation of the data by rock type, was necessary to distinguish the anomaly related to mineralization. Trace-element content in the heavy-mineral concentrates was dominated by the presence of the sulphide minerals pyrite, chalcopyrite, and sphalerite, thus directly reflecting mineralization.Use of the heavy-mineral fraction of the rock eliminates the dilution effects of quartz and feldspar, allowing enhancement of trace-metal concentrations in sulphide minerals, and the delineation of strong and extensive halos of Cu, Pb, Zn, Ag and Mn around the South Bay massive sulphide deposit. While the cost of preparation of heavy-mineral separates is higher than that for whole-rock samples, the anomaly clearly defined by the trace-element content of the heavy fraction avoids the need for costly major-element and subsequent statistical analysis, and increases target size by an order of magnitude. The heavy-mineral fraction obtained from rocks shows great potential as an exploration guide to volcanogenic massive sulphide deposits.  相似文献   

17.
Concentrations of chalcophile elements (As, Co, Cu, Hg, Mo, Ni, Pb, Sb and Zn) in western Canadian coals were determined using INAA and AAS. The concentrations of these elements in western Canadian coals are within the range for most world coals. However, there are some high values for coals from outcrops and from areas which are not currently being mined.Arsenic content in the majority of western Canadian coals, particularly those currently being mined, is low (0.2–3 ppm). However, there are coals with high arsenic content; for example, lignites from Hat Creek A zone contain between 4.0 and 14.0 ppm As. In some samples from Comox and Suquash, the As concentration is as high as 240 ppm and 1400 ppm, respectively. The enrichment of As in high arsenic coals is related to the geology and nature of country rocks associated with the coal seams. The concentration of other elements for most western Canadian coals, particularly those being mined, are within the range for most world coals. In these coals, the concentration ranges (in ppm) of chalcophile elements are 0.3-3.6 for Sb, 0.8-4.6 for Co, 7–35 for Cu, <0.1 for Hg, 2–6 for Mo, 4–94 for Ni, 6–22 for Pb, 2–7 for Se and 7–110 for Zn.  相似文献   

18.
A geochemical rock- and soil-sampling program was carried out in the vicinity of eight concealed “Cyprus type” deposits, occurring in marginal mafic to intermediate metapillow lavas of the Troodos Ophiolite Complex. The mineralization of massive and stockwork sulfide ore is characterized by the predominance of pyrite, intergrown with less chalcopyrite and minor amounts of sphalerite.Background values of Hg are in the range of 8–12 ppb for soils and 3–6 ppb for surface rocks. Anomaly/background ratios of 10:1 (soils) and 5:1 (rocks) have been found only, where Hg migrated along channels formed by faults cutting shallow-seated mineralization. Here, Hg sometimes shows significant correlations with Cu, Zn, Ba and exceptionally with Co. However in one case an Hg anomaly in soils and surface rocks was detected directly over a deposit. The use of Hg as indicator element for these types of deposits is therefore limited. Buried mineralization may be delineated more distinctly by Cu, Zn and Ba.  相似文献   

19.
安徽二叠纪龙潭组煤中潜在毒害元素分布的因子分析研究   总被引：1，自引：0，他引：1  
运用因子分析法对安徽二叠纪龙潭组煤层中S、Fe、As、CA、Se、Hg、Ti和Zn等的分布规律进行了研究,研究了这些潜在毒害元素的相关关系,并结合元素地球化学知识给出了这些元素在煤中赋存状态的信息。结果表明:煤层中Pb以方铅矿形式存在于煤中;As、Hg、Sb主要赋存于次生黄铁矿中;Zn和Se主要赋存于闪锌矿中;从元素地球化学性质上讲,Cd应赋存于闪锌矿中,但由于其在煤中的含量较低,造成分析数据的误差较大,从而掩盖了它与Zn之间的相关关系;Ti的赋存状态较为复杂。  相似文献   

20.
淮南矿区煤中12种微量元素的赋存状态及环境效应   总被引：2，自引：0，他引：2  
为研究淮南矿区煤中微量元素的赋存状态和环境效应,在淮南矿区7个矿井共采集17个样品,采用电感耦合等离子质谱仪（ICP-MS）测定了12种微量元素的含量,分别利用聚类分析和因子分析,结合其地球化学性质,讨论了它们的赋存状态,并采用静态燃烧实验研究其挥发性。结果表明:研究的元素没有异常富集;Zn和Cu赋存于闪锌矿中,Cr、Pb和Cd被粘土矿物吸附,Ba可能赋存于铁白云石和方解石中,Ni、Mo、Co和As主要赋存于黄铁矿中,Be和Se以有机结合态存在;研究的元素大多不易挥发,但Zn和Pb易挥发,且含量较高,环境危害较大,Zn和Pb分别赋存于闪锌矿和粘土矿物中,可通过洗选脱除减小其危害。   相似文献   

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