首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
Atomic absorption analyses of 25 metallic spheroids from Barringer Meteorite Crater have been carried out for Fe, Ni, Co and Cu. In addition, electron microprobe analyses of 58 impactite metallic particles have been carried out for Fe, Ni and Co from four different impactite samples. The normalized Ni, Co and Cu contents of the spheroids were from 13–22 per cent, 0.8–1.3 per cent and 260–430 μg/g, respectively. These figures represent enrichment factors of 2–3 in the spheroids compared to analyses of the bulk meteorite. The Co/Ni and Cu/Ni ratios in the spheroids are close to the respective ratios in the bulk meteorite. This suggests that the spheroids were formed by preferential removal of iron by oxidation from a chemically homogeneous liquid.The impactite metallic particles had Ni contents from 10 to 95 per cent and Co contents from 0·3 to 4 per cent. The Co contents of these particles showed a positive correlation with Ni up to 60 per cent Ni and a negative correlation beyond 60 per cent Ni. Reaction of the impactite metallic particles with SiO2 of the target can explain these variations. Our findings show that extensive chemical reaction between projectile and target occurs at impact.  相似文献   

2.
There are two types of white, coarse-grained, Ca-Al-rich inclusions in Allende. Type A inclusions contain 80–85 per cent melilite, 15–20 per cent spinel, 1–2 per cent perovskite and rare plagioclase, hibonite, wollastonite and grossularite. Clinopyroxene, if present, is restricted to thin rims around inclusions or cavities in their interiors. Type B inclusions contain 35–60 per cent pyroxene, 15–30 per cent spinel, 5–25 per cent plagioclase and 5–20 per cent melilite. The coarse pyroxene crystals in Type B's contain >15 per cent Al2O3 and >1.8 per cent Ti, some of which is trivalent. Type A pyroxenes contain <9 per cent Al2O3 and <0.7 per cent Ti.Electron microprobe analyses of 600 melilite, 39 pyroxene, 35 plagioelase, 33 spinel and 20 perovskite grains were performed in 16 Type A, 1 intermediate and 9 Type B inclusions in Allende and 1 Type A in Grosnaja. Melilite composition histograms from individual Type A inclusions are usually peaked between Ak10 and Ak30 and are 15–20 mole % wide while those from Type B inclusions are broader, unpeaked and displaced to higher åkermanite contents. Most pyroxenes contain < 1 per cent FeO. All plagioclase is An 98 to An 100. Spinel is almost pure MgAl2O4. Perovskite contains small (< 1 per cent) but significant amounts of Mg, Al, Fe, Y, Zr and Nb.Inferred bulk chemical compositions of Type A inclusions are rather close to those expected for high-temperature condensates. Those of Type B inclusions suggest slightly lower temperatures but their Ca/Al ratio seems less than the Type A's, indicating that the Type B's may not be their direct descendants. Some textural features suggest that the inclusions are primordial solid condensetes while others indicate that they may have been melted after condensation. Fragmentation and metamorphism may have also occurred after condensation.  相似文献   

3.
台湾东北部的龟山岛浅海热液体系产生大量的热液自然硫.为了理解微量元素在自然硫中的富集规律和机制,采用激光剥蚀等离子体质谱仪（LA-ICPMS）对龟山岛自然硫进行了元素含量分析.结果显示,硫磺基底仅含有As、Se和Te等岩浆脱气产生的挥发性亲铜元素.Fe、Mn、Co、Ni等亲铁元素主要来自于安山岩基岩,富集于富铁或含硅包体中.Al、Zn、Ba、Pb、La、Ce、Au、Ag等元素显著富集于含硅包体中,表明这些元素受硅酸盐矿物控制.富铜包体具有最高的Hg、Pb、Zn等亲铜元素的单位富集程度.首次对龟山岛热液自然硫中的微量元素分布进行了原位微区分析,有助于理解微量元素在热液活动中的来源、分布和分配等地球化学行为.   相似文献   

4.
Atomic emission spectrographic analysis of the trace inorganic constituents of marine humic substances gave the following range of concentrations: Si, 200 ppm to > 2%; Al, 400 ppm to ~ 1%; Fe, 600–3000 ppm; Ca, 600 ppm to > 2%; Mg, 20–6000 ppm; Na, 600 ppm to > 2%; Ag, < 6–600 ppm; B, < 60–1000 ppm; Cu, 600–4000 ppm; Mn, 8–100 ppm; Mo, <20–3000 ppm; Ni, 100–1000 ppm; Pb, < 40–600 ppm; Sn, 40–600 ppm; Ti, < 20–2500 ppm; V, 20–200 ppm; Zn, 350–4500 ppm; Zr, < 60–500 ppm.Humic substances contain a sizeable portion of the Cu, Mo and Zn found in sediments, but are less important for Ni, Co and Pb, and are insignificant for the Mn, V and Fe content. The metals are mostly introduced into the humates during their diagenetic formation in sediment by dissolution of metals from various mineralogical phases. A precursor of the sedimentary humates, the polymeric organic material dissolved in interstitial water, contains most of the Cu and Zn, about half of the Ni, Fe and Co, and very little of the Mn found in interstitial water. Comparison of the data on humates with that obtained by H2O2 treatment of sediments indicates that Cu, Zn and possibly most of the Mo are associated with organic matter, but that Ni and Co are associated with sulfides.  相似文献   

5.
Microanalysis of native gold specimens has been hampered by the lack of a suitable reference material (RM) known to be sufficiently homogeneous at the scale of microanalytical sampling. The suitability of gold reference material AuRM2 for microanalysis was assessed. This RM was created for bulk analysis of refined gold and was only certified for homogeneity at the bulk scale. However, it contains trace elements in appropriate mass fraction ranges for analysis of native gold. This study was not intended to provide alternative mass fractions from the original certified values, only to assess its suitability for microanalytical methods. Micro‐scale (~ 3.4 μg sample mass) heterogeneity was calculated from measurement repeatability of LA‐ICP‐MS analyses of AuRM2 by factoring in signal (represented by counting statistics) and instrument set‐up‐specific variability (determined using measurement variability of a reference material known to be homogeneous). Elements determined to be homogeneous or to have minor heterogeneity (< 10% calculated heterogeneity RSD) are Mg, Al, Ti, Fe, Ni, Cu, Zn, Se, Rh, Sn, Sb, Pt and Pb. Elements with moderate heterogeneity (10–20% heterogeneity RSD) are: Mn, As, Pd, Te and Bi. Correlation of element mass fractions indicates that micro‐scale inclusions of chalcophile‐rich phases along grain boundaries may be responsible for some of the chemical heterogeneity. However, the level of heterogeneity is statistically negligible compared with the ranges of chemical signatures observed in sample populations of native gold. Therefore, AuRM2 is shown to be sufficiently homogenous at a micro‐scale for use as a RM for microanalysis of native gold.  相似文献   

6.
This study reports on trace metal uptake by the grass species Melinis repens, growing in roadside soils and sediments in tropical northeastern Australia. Median total Cu, Pb, Ni and Zn concentrations were significantly (P < 0.05) higher in road edge soils (Cu = 61.1 mg/kg, Pb = 97.3 mg/kg, Ni = 28.6 mg/kg, Zn = 729 mg/kg) than in background soils collected away from roads (Cu = 5.8 mg/kg, Pb = 11.2 mg/kg, Ni = 3.7 mg/kg, Zn = 21 mg/kg). Significantly (P < 0.05) elevated Zn values were recorded in the stems of the M. repens specimens growing on roadside soils (231.6 mg/kg dry weight of tissue) compared with those of grasses growing on background soils (40.8 mg/kg dry weight of tissue). Moreover, median Cu, Ni and Zn values in the roots of roadside grasses (Cu = 29.1 mg/kg, Ni = 2.73 mg/kg, Zn = 169 mg/kg) were significantly (P < 0.05) higher than their respective levels in the roots of background M. repens samples (Cu = 5.98 mg/kg, Ni = 0.70 mg/kg, Zn = 22 mg/kg). A greenhouse experiment showed that Cu and Zn in road sediments are labile and are available for uptake by M. repens. The studied roadside soils and sediments were leached with a diethylenetriaminepentaacetic acid–CaCl2–triethanolamine–HCl extraction solution, which proved to be a rudimentary indicator of Zn availability and uptake to the root tissue of M. repens. The results demonstrate that trace metals in roadside grasses have the potential to be directed up the food-chain as grasses are consumed by herbivores. In addition, bioavailable metal contaminants hosted by road sediments have the capacity to impact on ecosystems downstream of roads because these sediments are mobilised by road runoff waters from road surfaces into adjoining catchments.  相似文献   

7.
High-precision Ni isotopic variations are reported for the metal phase of equilibrated and unequilibrated ordinary chondrites, carbonaceous chondrites, iron meteorites, mesosiderites, and pallasites. We also report new Zn and Cu isotopic data for some of these samples and combine them with literature Fe, Cu, and Zn isotope data to constrain the fractionation history of metals during nebular (vapor/solid) and planetary (metal/sulfide/silicate) phase changes.The observed variations of the 62Ni/58Ni, 61Ni/58Ni, and 60Ni/58Ni ratios vary linearly with mass difference and define isotope fractionation lines in common with terrestrial samples. This implies that Ni was derived from a single homogeneous reservoir. While no 60Ni anomaly is detected within the analytical uncertainties, Ni isotopic fractionation up to 0.45‰ per mass-difference unit is observed. The isotope compositions of Ni and Zn in chondrites are positively correlated. We suggest that, in ordinary chondrites, exchange between solid phases, in particular metal and silicates, and vapor followed by mineral sorting during accretion are the main processes controlling these isotopic variations. The positive correlation between Ni and Zn isotope compositions contrasts with a negative correlation between Ni (and Zn) and Cu isotope compositions, which, when taken together, do not favor a simple kinetic interpretation. The observed transition element similarities between different groups of chondrites and iron meteorites are consistent with the genetic relationships inferred from oxygen isotopes (IIIA/pallasites and IVA/L chondrites). Copper is an exception, which we suggest may be related to separate processing of sulfides either in the vapor or during core formation.  相似文献   

8.
 The Ganga Plain is one of the most densely populated regions and one of the largest groundwater repositories of the Earth. For several decades, the drainage basin of the Ganga Plain has been used for the disposal of domestic and industrial wastes which has adversely affected the quality of water, sediments and agricultural soils of the plain. The concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, Zn and organic carbon were determined in river sediments and soils of the Ganga Plain in the Kanpur-Unnao industrial region in 1994 and 1995 (pre-monsoon period of April–May). High contents (maximum values) of C-org (12.0 wt. %), Cr (3.40 wt. %), Sn (1.92 wt. %), Zn (4000 mg/kg), Pb (646 mg/kg), Cu (408 mg/kg), Ni (502 mg/kg) and Cd (9.8 mg/kg) in sediments (<20 μm fraction); and C-org (5.9 wt. %), Cr (2.16 wt. %), Sn (1.21 wt %), Zn (975 mg/kg) and Ni (482 mg/kg) in soils (<20 μm) in the pre-monsoon period of 1994 were found. From 1994 to 1995 the contents of Fe and Sn in sediments increase whereas those of C-org, Cd, Cu, Ni and Zn decrease. Considering the analytical errors, Al, Co, Cr, Mn and Pb do not show any change in their concentrations. In soils, the contents of Cd, Fe and Sn increase whereas those of Ni decrease from 1994 to 1995. Aluminium, Co, Cr, Cu, Mn, Pb and Zn do not show any change in their concentrations from 1994 to 1995. About 90% of the contents of Cd, Cr and Sn; 50–75% of C-org, Cu and Zn; and 25% of Co, Ni and Pb in sediments are derived from the anthropogenic input in relation to the natural background values, whereas in soils this is the case for about 90% of Cr and Sn; about 75% of Cd; and about 25% of C-org, Cu, Ni and Zn. The sediments of the study area show enrichment factors of 23.6 for Cr, 14.7 for Cd, 12.2 for Sn, 3.6 for C-org, 3.2 for Zn, 2.6 for Cu and 1.6 for Ni. The soils are enriched with factors of 10.7 for Cr, 9.0 for Sn, 3.6 for Cd, 1.8 for Ni and 1.5 for Cu and Zn, respectively. Received: 3 March 1998 · Accepted: 15 June 1998  相似文献   

9.
The spatial and temporal variations of Fe, K, Co, V, Cr, Cu, Ni, Zn, and Pb were determined in the sediments of Taihu Lake, the third largest freshwater lake in China and categorized into natural origin (Fe, K, Co, and V) and human contamination (Cr, Cu, Ni, Zn, and Pb) groups by principal component analysis. Most of the metals were positively correlated with the clay content (<4???m) and negatively correlated with the >16???m fraction, indicating the dominant role of grain size in regulating metals concentrations. Geochemical normalization and enrichment factors (EFs) were introduced to reduce the confounding of variable grain size and to quantify anthropogenic contributions. Higher EF values for Cr, Cu, Ni, and Zn occurred in the north Zhushan, Meiliang, and Gonghu Bays, indicating a high level of human contamination from the northern cities, such as Wuxi and Changzhou. Higher EF values of Pb were also present in the southwest and east lake areas, denoting the existence of additional anthropogenic sources. Chrome, Cu, Ni, Zn, and Pb showed increasing EF values in the top layers of sediment cores, indicating enhancing contamination since 1970s with rapid economy development in the catchment. These results indicate that geochemical normalization is a necessary and effective method in quantifying heavy metals contamination, and that historic sediment should be used as background values in calculating EFs. Potential risks of the heavy metals were assessed linking the consensus-based sediment quality guidelines and human contamination. Concentrations of Ni and Cr are greater than the threshold effect concentration (TEC) values, even in the sediments before 1970s, due to higher background concentrations in terrestrial parent materials. Concentrations of Ni and Cr are generally lower than the probable effect concentration (PEC) values, and concentrations of Cu and Zn are below the TEC values in the open lake areas. Whereas, concentrations of Ni and Cr are surpassing the PEC values and Cu and Zn are surpassing the TEC values in the north bays due to the high level of human contamination, where they were with EFs over 1.2, denoting higher potential eco-risks.  相似文献   

10.
Isotopic fractionation of Cu in tektites   总被引：1，自引：0，他引：1  
Tektites are terrestrial natural glasses of up to a few centimeters in size that were produced during hypervelocity impacts on the Earth’s surface. It is well established that the chemical and isotopic composition of tektites is generally identical to that of the upper terrestrial continental crust. Tektites typically have very low water content, which has generally been explained by volatilization at high temperature; however, the exact mechanism is still debated. Because volatilization can fractionate isotopes, comparing the isotopic composition of volatile elements in tektites with those of their source rocks may help to understand the physical conditions during tektite formation.Interestingly, volatile chalcophile elements (e.g., Cd and Zn) seem to be the only elements for which isotopic fractionation is known so far in tektites. Here, we extend this study to Cu, another volatile chalcophile element. We have measured the Cu isotopic composition for 20 tektite samples from the four known different strewn fields. All of the tektites (except the Muong Nong-types) are enriched in the heavy isotopes of Cu (1.98 < δ65Cu < 6.99) in comparison to the terrestrial crust (δ65Cu ≈ 0) with no clear distinction between the different groups. The Muong Nong-type tektites and a Libyan Desert Glass sample are not fractionated (δ65Cu ≈ 0) in comparison to the terrestrial crust. To refine the Cu isotopic composition of the terrestrial crust, we also present data for three geological reference materials (δ65Cu ≈ 0).An increase of δ65Cu with decreasing Cu abundance probably reflects that the isotopic fractionation occurred by evaporation during heating. A simple Rayleigh distillation cannot explain the Cu isotopic data and we suggest that the isotopic fractionation is governed by a diffusion-limited regime. Copper is isotopically more fractionated than the more volatile element Zn (δ66/64Zn up to 2.49‰). This difference of behavior between Cu and Zn is predicted in a diffusion-limited regime, where the magnitude of the isotopic fractionation is regulated by the competition between the evaporative flux and the diffusive flux at the diffusion boundary layer. Due to the difference of ionic charge in silicates (Zn2+ vs. Cu+), Cu has a diffusion coefficient that is larger than that of Zn by at least two orders of magnitude. Therefore, the larger isotopic fractionation in Cu than in Zn in tektites is due to the significant difference in their respective chemical diffusivity.  相似文献   

11.
The southwestern Sabzevar basin is the north of Central Iranian Microcontinent hosts abundant mineral deposits, including exhalative Mn mineralization and Cu-Zn volcanogenic massive sulfide (VMS) deposits. Amongst them, the Nudeh Besshi-type Cu–Zn volcanogenic massive sulfide (VMS) deposit is hosted within the lower part of a Late Cretaceous volcano-sedimentary sequence composed of alkali olivine basalt flows and tuffaceous silty sandstone. Based on investigations into the ore geometry, mineralogy, and texture, we recognized three different ore facies: (1) a stockwork of sulfide-bearing quartz veins cutting across the footwall volcano-sedimentary rocks and representing the stringer zone; (2) a massive ore type, displaying replacement texture with pyrite, chalcopyrite, sphalerite, friedrichite, and minor magnetite; and (3) a bedded ore type, with laminated to disseminated pyrite and chalcopyrite. EPMA studies indicate a distinctive minor element distribution between the different ore types of the Nudeh deposit. The Fe content in the sphalerite ranges from 0.65–1.80?wt.%, indicating the Fe-poor nature of the sphalerite. However, the Cd content in sphalerite ranged between 0.164–0.278?wt.%. According to the mineral compositions, Zn, Se, and Ag are found in bornite as minor elements. In the bedded ore facies, the pyrite contains higher levels of Se (up to 0.35?wt.%). The Zn content in the friedrichite in all of the ore samples is low. The Co/Ni ratios in pyrite from the Nudeh ore are lower than those of most magmatic deposits, but are similar to those from volcanogenic deposits, and hence support the proposed hydrothermal origin of the deposit. Two generations of quartz, Q1 and Q2 in the stockwork veins, contain primary fluid inclusions and these contain two phases (liquid and vapor). The lack of vapor-rich inclusions or variable liquid/vapor ratios indicate that the fluids did not boil at the site of trapping. Salinity for both Q1 and Q2 fluid inclusions ranges between 2.2–6.8?wt.% eq. NaCl. Homogenization temperatures for inclusions in the Q1 and Q2 veins average at about 296?°C and are similar to the temperatures of hydrothermal fluids discharged through vents in many modern seafloor VMS deposit. The Nudeh Besshi-type VMS deposit appears to have formed on the seafloor and based on the salinity and temperature constraints from the underlying stockwork, a buoyancy plume model is proposed as a mechanism for precipitation.  相似文献   

12.
Fluid inclusions in quartz from the Lannigou and Yata Carlin-type gold deposits in southwestern Guizhou were analyzed by inductively coupled plasma-mass spectrometry for their trace elements(Co,Ni,Cu,Pb,Zn,Pt,etc.).The results show that quartz fluid inclusions entrapped at different ore-forming stages contain higher Co,Ni,Cu,Pb and Zn.It has been found for the first time that the ore-forming fluids responsible for the Carlin-type gold deposits are rich in Pt.From this it can be concluded that basic volcanic rocks seem to be one of the important sources of ore-forming materials for the Carlin-type gold deposits.  相似文献   

13.
徐平  陈友红 《岩石学报》1996,12(1):163-168
作者利用质子微探针和微束ＰＩＸＥ定量分析技术，对山东梭罗树地幔橄榄岩中橄榄石、斜方辉石、单斜辉石、尖晶石和石榴石等矿物的微量元素组成与分布进行了研究。结果表明，不相容元素（Ｓｒ，Ｙ，Ｚｒ）主要富集于单斜辉石内，尖晶石则几乎富集质子探针所能检出的所有微量元素，而石榴石中微量元素含量最少。研究表明，微区微量元素分布很不均匀，推测可能受地幔交代过程中溶液的渗滤效应以及存在微粒包裹体的共同制约。  相似文献   

14.
作者利用质子微探针和微束ＰＩＸＥ定量分析技术，对山东梭罗树地幔橄榄岩中橄榄石、斜方辉石、单斜辉石、尖晶石和石榴石等矿物的微量元素组成与分布进行了研究。结果表明，不相容元素（Ｓｒ，Ｙ，Ｚｒ）主要富集于单斜辉石内，尖晶石则几乎富集质子探针所能检出的所有微量元素，而石榴石中微量元素含量最少。研究表明，微区微量元素分布很不均匀，推测可能受地幔交代过程中溶液的渗滤效应以及存在微粒包裹体的共同制约。  相似文献   

15.
 The Yamuna River sediments, collected from Delhi and Agra urban centres, were analysed for concentration and distribution of nine heavy metals by means of atomic adsorption spectrometry. Total metal contents varied in the following ranges (in mg/kg): Cr (157–817), Mn (515–1015), Fe (28,700–45,300), Co(11.7–28.4), Ni (40–538), Cu (40–1204), Zn (107–1974), Pb (22–856) and Cd (0.50–114.8). The degree of metal enrichment was compared with the average shale concentration and shows exceptionally high values for Cr, Ni, Cu, Zn, Pb and Cd in both urban centres. In the total heavy metal concentration, anthropogenic input contains 70% Cr, 74% Cu, 59% Zn, 46% Pb, 90% Cd in Delhi and 61% Cr, 23% Ni, 71% Cu, 72% Zn, 63% Pb, 94% Cd in Agra. A significant correlation was observed between increasing Cr, Ni, Zn, and Cu concentrations with increasing total sediment carbon and total sediment sulfur content. Based on the Müller's geoaccumulation index, the quality of the river sediments can be regarded as being moderately polluted to very highly polluted with Cr, Ni, Cu, Zn, Pb and Cd in the Delhi and Agra urban centres. The present sediment analysis, therefore, plays an important role in environmental measures for the Yamuna River and the planning of these city centres. Received: 21 June 1999 · Accepted: 1 October 1999  相似文献   

16.
All varieties of base metal sulphide deposits may be classified using base metal ratios viz. Copper Ratio (CR=100Cu/{Cu+Zn}), Zinc Ratio (ZR=100Zn/{Zn+Pb}) and Lead Ratio (PR=100Pb/{Pb+Cu}). Based on this ore group classification an attempt has been made to identify ore groups present in the late Archaean volcanic associated Ingaldhal Sulphide Deposit (ISD) of Karnataka Craton. Using base metal ratios (CR, ZR and PR) five distinct fields are suggested: Cu, Cu-Zn, Cu-Zn-Pb, Zn-Cu and Zn-Cu-Pb/Zn-Pb-Cu with their associated geological and geochemical characteristics. A transitional change in the ore groups is observed from the North Block (Cu rich groups; CR>50) to South Block (Zn and Pb dominated groups; CR<50) and the Main Block is represented by all the five ore groups.This classification may be useful as a pointer in the exploration of polymetallic base metal deposits. Copper rich groups (Cu, Cu-Zn and Cu-Zn-Pb) exhibit high concentration of Bi and Co, and low CaO and Cd whereas the Zn rich groups (Zn-Cu and Zn-Cu-Pb/Zn-Pb-Cu) show high CaO and Cd, and low Bi and Co. The CR of most of the ore groups exhibit a sympathetic relation with Co and Ag. A preliminary attempt has been made for better understanding of ore group genesis of ISD by integrating ore group characteristics with deduced geothermometry.  相似文献   

17.
Radiochemical neutron activation analysis has been used to determine Ni, Zn, Ga, Ge, Cd, In, Ir and Au in duplicate samples of lunar soil 14141 and one additional replicate each of soils 14163 and 14259. The concentrations of extralunar trace elements Ni, Ge, Ir and Au in 14141 and 14163 are, respectively, about 69 and 82 per cent as high as those in 14259. Although most of the mass of 14141 appears to be ejecta from Cone Crater, a sizable contamination by mature Fra Mauro soil such as 14259 is also present. The siderophilic-element concentrations of the subregolith Fra Mauro materials are estimated to be 25 ± 25 per cent of those observed in 14259.  相似文献   

18.
Authigenic pyrite grains from a section of the Lower Toarcian Posidonia Shale were analysed for their trace‐element contents and sulphur‐isotope compositions. The resulting data are used to evaluate the relationship between depositional conditions and pyrite trace‐element composition. By using factor analysis, trace‐elements in pyrite may be assigned to four groups: (i) heavy metals (including Cu, Ni, Co, Pb, Bi and Tl); (ii) oxyanionic elements (As, Mo and Sb); (iii) elements partitioned in sub‐microscopic sphalerite inclusions (Zn and Cd); and (iv) elements related to organic or silicate impurities (Ga and V). Results indicate that trace‐element contents in pyrite depend on the site and mechanism of pyrite formation, with characteristic features being observed for diagenetic and syngenetic pyrites. Diagenetic pyrite formed within anoxic sediments generally has a high heavy metals content, and the degree of pyritization of these elements increases with increasing oxygen deficiency, similar to the degree of pyritization of reactive Fe. The highest gradient in the increase of the degree of trace element pyritization with bottom‐water oxygenation was found for the elements Ni < Cu < Mo = As < Tl. In contrast, syngenetic pyrite formed within a euxinic water column typically is enriched in As, Mo and Sb, but is low in heavy metals, and the geochemical variation reflects changes in sea water composition.  相似文献   

19.
近50年来抚仙湖重金属污染的沉积记录*   总被引：15，自引：8，他引：15  
文章以抚仙湖污染严重的北部和基本未受人类活动影响的中部为研究对象,分别采集了沉积岩芯FB和FZ,通过对岩芯的137 Cs测年和重金属元素(Cu,Ni,Ti,Cr,V,Pb,Cd和Zn)的含量分析,研究了湖泊重金属来源和污染历史,并利用地质累积指数法评价了湖泊重金属污染程度。结果表明:抚仙湖北部的平均沉积速率约为2.0~2.8mm/a;20世纪80年代以前,湖泊北部和中部的重金属元素(Cu,Ni,Ti,V,Pb,Cd,Zn)以自然来源为主;80年代以后,抚仙湖受到人类活动的影响,但湖泊中部Cu,Ni,Ti,V,Pb,Zn以及湖泊北部Cu,Ni,Ti,V仍以自然来源为主;湖泊北部Pb和Zn地质累积指数值小于1,属无污染到中度污染;北部Cd地质累积指数为3~4,达强度污染;中部Cd地质累积指数为2~3,属中强度污染;且Pb,Zn和Cd污染程度有加速增大的趋势。  相似文献   

20.
The comparative behaviour of Ni, Cu and Zn in the system “mine tailings–ground water–plants” has been investigated at the Ni–Cu mine site operated by INCO Ltd. Thompson Operations, Thompson, Manitoba. Oxidation of sulphide minerals causes the release of metals from exposed tailings containing Ni ∼2000 ppm, Cu ∼150 ppm and Zn ∼100 ppm to the ground water, which contains 350 mg/L Ni, 0.007 mg/L Cu, and 1.6 mg/L Zn. The metal concentration in the ground water is affected by the relative proportions of sulfide minerals, the rate of oxidation of sulphide minerals (Ni-bearing pyrrhotite > sphalerite > chalcopyrite), and the affinity of the metals for secondary Fe-phases (Ni > Zn > Cu).  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号