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1.
Characterization of zeolitic tuff from Jabal Hannoun (HN) and Mukawir (MR) was carried out to examine the ability of using low-cost natural materials in domestic wastewater treatment. The grain size between 0.3 and 1 mm (0.3–1 mm) of the HN and MR has the highest total zeolite grade (faujasite–phillipsite and phillipsite–chabazite) and suitable cation exchange capacity. They were used as fixed-bed ion exchangers and adsorbents. The zeolitic tuff efficiently removed the organic and nitrogen compounds, Pb and Zn from the effluent. One bed volume (1 BV) of the zeolitic tuff is capable to remove up to 95 % of total organic carbon form 500 BV of the effluent. The removal percent of total nitrogen by HN and MR is close to 95 and 90 %, respectively. The zeolitic tuff has an excellent efficiency to remove Pb and Zn from the effluent. 1 BV of HN completely cleans Zn and Pb from 680 and 730 BV of the effluent, respectively, whereas 1 BV of MR is able to clean completely Zn and Pb from 500 and 685 BV of the effluent, respectively. The greater performance of the HN compared with the MR may be explained by its higher zeolites grade and presence of faujasite.  相似文献   

2.
Chabazite-phillipsite tuff from Tell Rimah volcano was evaluated in industrial wastewater treatment. Samples of two different size fractions have suitable zeolite content and cation exchange capacity, and are characterized by good attrition resistance and high packed bed density. Such properties enable these fractions to be used as ion exchangers under column operation condition. In the presence of high concentration of competing ions, such as Na+, Ca+2 and K+, and under conditions of high total ionic concentration of toxic metals, the chabazite-phillipsite tuff exhibits successful performance in removing Cu+2, Cr+3, Ni+2, Zn+2 and Fe+2 from electroplating effluents. The factors that influence selectivity and efficiency of the zeolitic tuff were evaluated. The experimental work indicates that both selectivity and efficiency of the zeolite shows similar trends. The selectivity sequence exhibited by the zeolitic tuff is Ni+2>>Zn+2 and Cr+3>Cu+2>>Fe+2.  相似文献   

3.
Physical and chemical characterization of spent oil shale (OS) from El-Lajjun area has been carried out and compared with the original OS. The spent shale (SS) is subjected to leaching tests to detect the possibilities of heavy metals released from it into the environment. Standard column leaching experiments have revealed no detectable release of heavy metals to the percolating water. The effectiveness of the SS in removing Pb2+ from wastewater has been investigated. The SS is very efficient in removing most of Pb2+ where 1 m3 of SS has an efficiency to remove from 64 to 94% of Pb2+ from about 1,300 m3 wastewater sample containing 50 ppm Pb2+. The efficiency decreases substantially with increasing Pb2+ concentration in the wastewater. In real situations, where Pb2+ concentration is very low (i.e., less than 5 ppm), the efficiency of the SS is expected to be 100%.  相似文献   

4.
Passive treatment systems have become one of the most sustainable and feasible ways of remediating acid mine drainage (AMD). However, conventional treatments show early clogging of the porosity or/and coating of the reactive grains when high acidity and metal concentrations are treated. The performance of fine-grained reagents dispersed in a high porosity matrix of wood shavings was tested as an alternative to overcome these durability problems. The system consisted of two tanks of 3 m3 filled with limestone sand and wood shavings, and one tank of 1 m3 with caustic magnesia powder and wood shavings, separated by several oxidation cascades and decantation ponds. The system treated about 1.5 m3/day of AMD containing an average of 360 mg/L Fe, 120 mg/L Al, 390 mg/L Zn, 10 mg/L Cu, 300 μg/L As and 140 μg/L Pb, a mean pH of 3.08 and a net acidity of 2500 mg/L as CaCO3 equivalent. The water reached pH 5 and 6 in the first and second limestone tanks, respectively (suitable to remove trivalent metals); and pH 8–9 in the MgO tank (suitable to remove divalent metals). After 9 months of operation, the system achieved an average removal of 100% Al, Cu, As, Pb, more than 70% Fe, about 25% Zn and 80% acidity. Goethite, schwertmannite, hydrobasaluminite, amorphous Al(OH)3 and gypsum were the main precipitates in the two limestone tanks. Precipitation of divalent metals (Fe (II), Zn, and traces of Cd, Ni and Co) were complete inside the third tank of MgO, but preferential flow along the walls was responsible for its low treatment performance. Goethite, gypsum, Zn-schulenbergite and sauconite are the crystalline solid phases identified in the MgO tank.  相似文献   

5.
Jamaica Bay, NY, is a highly urbanized estuary within the boroughs of New York City conspicuously lacking published information on dissolved trace metal concentrations. The current study examines the distribution and cycling of trace metals in that embayment with data gathered during cruises in November 2004, April 2005, and June 2006. Most of the metal distributions (Fe, Zn, Co, Ag, Cu, Pb, Ni) in the water column are explained by the input of substantial volumes of treated wastewater effluent. However, several lines of evidence suggest that submarine groundwater discharge (SGD) is also an important source of dissolved Fe, Zn, Co, Ni, and isotopically distinct stable Pb ratios (206Pb, 207Pb, 208Pb) in the Bay. Conversely, the recirculated seawater component of SGD is an apparent sink for dissolved Mo. This study provides the first measurements of dissolved trace metals in the Jamaica Bay water column and subterranean estuary and provides evidence for trace metal input due to SGD.  相似文献   

6.
A promising technique for the removal of heavy metal ions from wastewater streams involved firstly the ions adsorption on a colloidal precipitate (carrier) and then the separation of the loaded flocs (coagula) by a modified column flotation. Here, the effluent feed and the carrier (ferric hydroxide) enter smoothly by the top of the column through a special diffuser, in counter current with rising bubbles (100–600 μm diameter) generated by using recycled water, surfactant and air suction through a venturi. High separation values of the column flotation of the carrier precipitates were achieved, despite the high superficial flow rate and the high Fe+ 3 concentration utilized (> 60 mg L− 1 Fe). No rupture of colloidal carrier aggregates was observed and a low split was ensured by monitoring the concentrate (floated product) flow rate. Results indicated that best separation was attained by controlling the medium pH (for best heavy metal ion adsorption onto the carrier), followed by sodium oleate, used as “collector” and optimizing operating parameters (conditioning, flow rates, etc.). The column throughput reached 43 m h− 1 (m3 m− 2 h− 1), which is about 4 times the normal capacity of DAF-dissolved air flotation unit, the most used floater in wastewater treatment. Various metals (Cu, Ni, Pb, etc.) and molybdate ions present in synthetic and real effluent were successfully removed based on this colloidal adsorbing flotation principle. The process was also applied in a pilot scale to treat an industrial electroplating wastewater. Most of toxic metals (Cu, Ni and Zn) were reduced from initial concentrations of about of 2 to 10 mg L− 1, to below 0.5 to 1.0 mg L− 1, meeting local municipal discharge limits (but Cd ions). It is believed that flotation separation using medium-sized bubbles has great potential as a clean water and wastewater treatment technology.  相似文献   

7.
Natural zeolitic rocks consisting mainly of chabazite-phillipsite, clinoptilolite, and volcanic glass have been evaluated by means of batch methods to remove arsenic from waters with different mineralization degree (from deionized water to natural water with a specific conductivity of 1,600 μS cm− 1). Arsenic was previously spiked in the studied waters at concentrations of about 100 µg l− 1 to simulate actual cases. The compositional range of natural waters is representative of large hydrogeochemical regions around the world. The experiments were focussed on the application of natural common zeolitic rocks to water treatment for human consumption. The removal efficiency observed rises, in the better cases, 60–80% for chabazite-phillipsite raw materials whereas is 40–60% for clinoptilolite-bearing ones. The arsenic removal tends to increase with water mineralization degree, independently of the zeolitic rock type. A large zeolitic content in the chabazite-phillipsite raw materials increase the removal. Instead, the inverse situation is observed in the clinoptilolite-bearing rocks. The relevance of the quantitative mineralogical analysis, determining also the content of volcanic glass, as well as the use of natural waters in the removal tests has been demonstrated.  相似文献   

8.
Soil aquifer treatment (SAT) is an effective indirect technique for wastewater reuse. The present study aims at assessing the soil capacity in arid region of Varamin on natural attenuation of inorganic constituents of municipal treated wastewater of Tehran City. In order to simulate SAT pond, four columns of 30 cm in height and 4 cm in diameter were filled with sandy loam soil taken from artificial recharge pond in Varamin plain. These columns were recharged by secondary treated wastewater from Shahre-Rey treatment plant under the plan of 12-h wetting and drying cycles. During the experiment, 50 pore volume passed through each column. The pH, EC, TDS, SAL, SAR, major ions, nitrate, phosphate and trace elements were measured in influent and effluent samples. The concentration of Na+, Ca2+, Mg2+, Cl? and SO42? increased in effluent samples due to a washout process and dissolution of minerals. The soil could only attenuate NO3?, K+, Rb and PO43? with the percentage of 18.4, 24.6, 67.7 and 83.6, respectively. The soil of studied area is rich in Cr, Ni, Sr, Pb, Cu, Zn, Ba and Rb. The concentrations of all mentioned trace elements, with the exception of Rb, have increased in the effluent samples with respect to influent. Also, the quality indices of TDS, SAL and SAR have increased 10.6, 25.2 and 8.7%, respectively, in effluent. Soil column samples, at the end of experiment, contain high amounts of major and trace elements. Consequently, there is a potential risk for groundwater contamination in long-term recharge.  相似文献   

9.
The study area is situated in a large agricultural field which produces tobacco, maize, and other yearly cultivated vegetables in Tekkeköy, Samsun (NE-Turkey). In addition, a significant part of this area to the north along the Black Sea coast is occupied by several industrial plants such as a copper smelting plant (KB?), a fertilizer plant (Tügsa?) and industrial park facilities (IPF). In order to reveal their environmental impacts, heavy metal analyses were conducted on soil, plant leaves and water samples collected within an area of approximately 30 km2 around these plants. Soil samples within an area of 10 km2 around these facilities are found to be highly polluted with Cu, Zn, Pb, Fe and Mn. Pollution occurs at surface and sharply dies out at 20 cm downwards in soil profile. Since the region is polluted mostly with base metals, the copper smelting factory appears to be the main source of pollution as it processes the massive sulfidic ores of the Black Sea area. Plants show Cu, Pb, Zn and Fe pollution around KB? and Tügsa? and Cu and Pb around IPF. Pollutants observed in tobacco (Nicotiana tobacum) are Cu, Pb, Zn, Fe and S; in maize (Zea mays) Cu, Zn and Fe; and in cabbage (Brassica oleracea) Cu, Pb, Fe and S. The analyses of water samples collected from the study area reveal that Pb and, to a lesser degree, Cu and Fe pollution stem from KB?; Cu, Fe and Mn pollution from Tügsa?; Pb and minor amounts of Fe and Mn pollution from IPF. Factor analyses from analyzed metals and anionic complexes in water show three distinct groups: (a) an association of heavy metals with Na, K and Mg referring to pollution and acid leaching of soil, (b) an association of NH4, Fe, SO4, Cl and Br indicating agricultural pollution and sea-water invasion in land near the shore line, and (c) HCO3 behaving in a different manner in heavy metal precipitation.  相似文献   

10.
《Applied Geochemistry》2003,18(11):1751-1756
Siderophores are low-molecular weight organic molecules secreted by plants and micro-organisms in response to Fe stress. With stability constants commonly exceeding 1030, siderophores are considered to have higher affinities for Fe(III) than for any other major or trace element dissolved in soil solution. However, several siderophores have affinities for trace metals that approach those for Fe(III), and certain actinides form siderophore complexes of surprisingly high stability. The purpose of this study was to examine the role of hydroxamate siderophores in controlling Pb sorption to an Fe(III) oxide adsorbent. Goethite [α-FeOOH], prepared by standard methods and identified by X-ray diffraction, gave a specific surface of 36 m2 g−1 as determined by N2 multipoint BET analysis. Adsorption experiments were performed aseptically using a batch method with a goethite concentration of 1.0 g l−1 and an ionic strength of 0.01 M NaClO4. Soluble Pb and Fe were measured between pH 3 and 8 by first adding Pb (10 μM) and then siderophore (10, 20, or 40 μM) to the goethite suspension. Three hydroxamate siderophores were employed: desferrioxamine B (DFB), ferrichrome (FC), and rhodotorulic acid (RA). Following 20 h reaction, Pb and Fe in solution were measured by ICP–MS and ICP–AES, respectively. The efficacy of siderophore-mediated Pb desorption varied with siderophore type and generally increased with pH and siderophore/Pb molar ratio. Desferrioxamine B, at pH 6.5 and a DFB/Pb molar ratio of 4, solubilised nearly 25% of the total sorbed Pb. In the presence of 10 μM FC, Pb adsorption largely mimicked that for the siderophore-free system, whereas significant amounts of Pb were desorbed with 20 μM FC at pH >5.5. The dihydroxamate siderophore, RA, was the least effective Pb chelator, requiring 20 μM to desorb detectable amounts of Pb.  相似文献   

11.
Seasonal variation in bacterial heavy metals biosorption from soap and brewery industrial effluent samples from Eziama River in Abia State were analyzed for Pb, Hg, Fe, Zn, As, and Mn, using atomic absorption spectrophotometry. Bioaccumulation of the metals by bacteria showed the following trend > Fe >Zn >As > Pb > Mn (Rainy Season) and Zn > Fe > Mn > As > Hg > Pb (Dry season). Statistical analysis using of variance (ANOVA) showed significant differences in concentrations of Pb, Hg, Fe, Zn, As, and Mn level between the sampling zones at Eziama River. Seasonal changes in heavy metal concentrations, showed increases in Pb, Fe, and As from 1.32 x 105 mg/L in the rainy season to 1.42 x 105 mg/L in the dry season. Fe increased from 40.35 x 105 mg/L to 42.1 x 105 mg/L, while As increased from 2.32 to 2.48 x 105 mg/L with a net increases of+56 and + 69 x 105 mg/L respectively. However, Hg, Zn, and Mn concentrations decreased in the rainy season from 40.54 x 105 mg/L to 39.24 x 105 mg/L, 1.65 to 0.62 x 105 mg/L respectively.  相似文献   

12.
The ability of light expanded clay aggregate to remove lead and cadmium from paint industry’s effluents was studied at different levels of adsorbent, contact time and pH in April 2008. For this purpose, lead and cadmium removal from paint industry effluents were studied in batch reactors. lead and cadmium measurements have been taken with non-flame atomic absorption techniques and test methods were adapted from 19th. Ed. of standard methods for the examination of water and wastewater. In this study, different amounts of Leca (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 g/L) were investigated. The amount of adsorbed lead and cadmium exposure to Leca increased from 1.41 to 3 mg/g and 0.22 to 0.75 mg/g, respectively. The maximum removal efficiency for Pb was 93.75 % at pH = 7 and exposure to 10 g/L of Leca, while for cadmium, it was nearly 89.7 % at the same condition. In this study, adsorption process of lead and cadmium was fitted with Freundlich adsorption isotherm (R2 Pb = 0.97 and R2 Cd = 0.98). The sufficient contact time was deemed 1–2 h for lead and cadmium. According to the results, Leca is recommended as a low cost and available adsorbent to remove lead and cadmium from industrial wastewater.  相似文献   

13.
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14.
Sediment and pore water samples have been collected from the coastal tidal flat in the Shuangtaizi estuary, China, in order to investigate the geochemical behavior of iron, cadmium, and lead during diagenesis and to assess the degree of contamination. The calculated enrichment factors and geoaccumulation indices for separate elements show that anthropogenic activities have had no significant influence on the distribution of Fe and Pb in the study area, whereas the distribution of Cd has been closely influenced in this way. The high percentage of exchangeable Cd (average of 56.34%) suggests that Cd represents a potential hazard to benthic organisms in the estuary. The calculated diffusive fluxes of metals show that the most mobilized metal is Fe (9.22 mg m?2 a?1), followed by Cd (0.54 mg m?2 a?1) and Pb (0.42 mg m?2 a?1). Low Fe2+ contents in surface pore water, alongside high chromium-reducible sulfur contents, and low acid-volatile sulfur, and elemental sulfur contents at 0–25 cm depth in sediments show that Fe2+ is formed by the reduction of Fe oxides and is transformed first to a solid phase of iron monosulfides (FeS) and eventually to pyrite (FeS2). The release of adsorbed Pb due to reductive dissolution of Fe/Mn oxides during early diagenesis could be a source of Pb2+ in pore water. From the relatively low total organic carbon contents measured in sediments (0.46–1.28%, with an average of 0.94%) and the vertical variation of Cd2+ in pore water, sulfide or Fe/Mn oxides (instead of organic matter) are presumed to exert a significant influence on carrying or releasing Cd by the sediments.  相似文献   

15.
《Applied Geochemistry》1997,12(1):75-81
The extent of vertical migration of anthropogenic Pb beneath a medieval smelting site in Derbyshire, U.K. has been estimated using the determination of total Pb concentrations and 206Pb/207Pb isotope ratio from samples taken down 6 m of drill core. Preliminary studies of total Pb concentrations established that the surface slag derived from the smelting contained up to 16% Pb and that the normal background levels in uncontaminated sandstone were 10±2 ppm. Sample analyses beneath the site revealed elevated Pb concentrations in fracture infill clays (270 ppm Pb) and sandstone (76–83 ppm Pb). Both are well above the background Pb concentration.Lead isotope analysis of the slag wastes, the underlying contaminated sandstone and fracture infill has shown that all 3 contain very similar isotope ratios for 206Pb/207Pb (1.1802–1.1820). However, matched control sandstone samples show that the background 206Pb/207Pb isotope ratio (1.1670 ± 0.003) is distinctly different. This would indicate that both the sandstone and fracture infill underlying the historical smelting site contain a substantial proportion of Pb that has been derived from the overlying contamination.The application of total Pb concentrations along the core and isotope analysis suggest that anthropogenically derived Pb from the smelting site (that was operated between 665 and 445 a BP) has migrated to a depth of 4.50 m. Assuming a uniform migration rate and a mean time of migration of 555 a, then the mean migration rate is estimated to be 8 ± 2 mm/a.The proportion of natural versus anthropogenic Pb in the samples has been estimated from small variations in the 206Pb/207Pb isotope ratio. If the slag is considered to contain 100% anthropogenic Pb and the uncontaminated sandstone considered to contain 100% natural Pb, the linear interpolation can be applied between the 2 end members of the isotope ratio. The use of this approach to the 206Pb/207Pb ratio measurements has shown that 88% of the Pb in the contaminated sandstone (i.e. 69 ppm from a mean total Pb concentration of 78.5 ppm) has been derived from the anthropogenic Pb at the surface. For the fracture infill sample taken at a depth of 4.50 m, and with a total Pb concentration of 270 ppm, the % of Pb that has been derived from the slag wastes is approximately 98% (equivalent to 265 ppm Pb). The remaining Pb in both these samples (9.4 and 5 ppm, respectively) is deduced to have originated from the natural background concentration of Pb in the sandstone.The closeness of these estimates to the measured background concentration, suggests that a simple two-source model of Pb contamination is valid for this site.  相似文献   

16.
Health hazards from heavy metal pollution in water systems are a global environmental problem. Of similar concern is sludge that results from wastewater treatment due to unsatisfactory sludge management technology. Therefore, the effectiveness of using Mg–Al-layered double hydroxide in the removal of heavy metals from mine wastewater was tested and compared with that of calcium hydroxide [Ca(OH)2], which is a common treatment method for heavy metal removal. Initially, the mine wastewater contained cations of the heavy metals iron (Fe), zinc (Zn), copper (Cu), and lead (Pb). The Mg–Al-layered double hydroxides were able to remove 371, 7.2, 121, and 0.4 mg/L of these pollutants, respectively, using the co-precipitation method. The removal of these metals is most effective using 0.5 g Mg–Al-layered double hydroxide (Mg/Al molar ratio 4) and 20 min of shaking. Zn was removed by the formation of Zn(NO3)(OH)·H2O and Zn5(NO3)2(OH)8 when LDH, Mg/Al molar ratios of 4 and 2, respectively, were used. Similarly, Fe, Cu, and Pb were removed by the formation of Fe–Al-layered double hydroxide, Cu2(OH)3·NO3 and Pb4(OH)4(NO3)4, respectively. While Ca(OH)2 is also capable of reducing the heavy metal concentrations below the Japanese recommended values, this analysis shows that using 0.5 g Mg–Al-layered double hydroxide is a better treatment condition for mine wastewater, because it generates lower sludge volumes than 0.1 g of Ca(OH)2. The measured sludge volume was 1.5 mL for Mg–Al-layered double hydroxide and 2.5 mL for Ca(OH)2, a nearly twofold further reduction.  相似文献   

17.
The weathered surface expression of the Lady Loretta lead-zinc-silver deposit outcrops almost continuously over a distance of about 4 km. Lead isotope ratios have been determined for samples, some of which contain > 4000 ppm Pb, from geochemically anomalous areas in order to assign drilling priorities to the anomalies.Twelve of the 43 samples analyzed contain isotopically homogeneous lead with ratios (207Pb/206Pb 0.9532–0.9549) similar to the expected targets for major ore deposits in the Mount Isa-McArthur River metallogenic province (207Pb/206Pb 0.955–0.962). Three main zones of interest can be outlined on the basis of lead isotopic data. The top priority is assigned to a 100-m-long section of the ironstone which coincides with the known outcrop of the ore. Lower priority for drilling is given to the two other zones which outcrop over smaller areas and have more radiogenic lead in their immediate surroundings. Several samples with anomalously high lead contents (> 1000 ppm) contain more radiogenic lead (207Pb/206Pb < 0.950) which was most likely derived from the weathering country rocks by supergene leaching and redeposition. Of the 22 samples containing ≥ 380 ppm Pb, lead isotopic analyses would have reduced the number deserving further attention to 10. Lead isotopic analyses in the early stages of exploration could have assisted in minimizing exploration expenditure at Lady Loretta.  相似文献   

18.
《Applied Geochemistry》1997,12(2):203-211
The metal attenuation capacities of secondary acid mine water precipitates is dependent upon such factors as pH, ionic strength, the presence of competing ions, and tailings mineralogy. At the abandoned Spenceville Cu mine in Nevada County, California, approximately 6800 m3 of jarosite overburden and 28,000 m3 of hematite residue are potential sources of heavy metals loading to infiltrating surface waters. A column study was performed to assess the ability of the overburden and the residue to attenuate heavy metals from acidic mine drainage. The study information was needed as part of a remedial design for the abandoned mine, and was designed to simulate a worst-case scenario to examine the plausibility of backfilling a large open pit with the waste materials. Ten pore volumes of acidic mine drainage were allowed to pass through the materials, and the column effluents were analyzed for dissolved Fe, Al, Ca, Mg, Na, K, Mn, Cu, Zn, Pb and Ni using ICP-AES. The oxidation-reduction potential (Eh) was measured with a combination PtAg/AgCl electrode and also calculated from Fe(II) and Fe(III) measurements using the Nernst equation. Ion activities in solution and saturation index (SI) values for various solid phases were calculated using the geochemical speciation model MINTEQA2, and mineralogical compositions of fine (< 2 mm) and coarse ( > 2 mm) fractions were determined by XRD. Geochemical modeling of the column effluent compositions indicate that goethite, jarosite, jurbanite and gypsum are potential solid phases that may control metal solubilities in the column effluents. Excellent agreement was observed between the measured Eh values and those calculated from the activity ratio of Fe2+(aq) to Fe3+(aq). The large attenuation capacities for Cu and Zn exhibited by the jarosite overburden also suggest that solid solution substitution plays a large role in controlling metal concentrations in the pore waters. Relatively little metal attenuation, however, was provided by the hematite residue.  相似文献   

19.
Wastewater treatment with bioelectrical generation is an attractive feature with microbial fuel cells. The chitosan/biodegradable copolymer proton exchange membrane was used to assess its performance with brewery wastewater in a dual chambered microbial fuel cell. The biodegradable copolymer was made by thermal condensation of malic acid and citric acid in 3:1 ratio and then blended with chitosan to form a membrane via solution casting and solvent evaporation techniques. The performance of the chitosan/biodegradable copolymer membrane was evaluated in bioelectricity production with brewery effluent as an anolyte in a carbon electrode microbial fuel cell. Additionally, the competence of the prepared blend proton exchange membrane is compared with the commercial Nafion 117 membrane and Agar salt bridge in separate microbial fuel cell units with the same effluent and electrodes. At neutral pH, the effect of adding metabolites such as glucose and acetate to the anolyte was also investigated. The maximum current density and power density generated with chitosan/biodegradable copolymer membrane was 111.94 mA m?2 and 3022.39 mW m?2, respectively, whereas the Nafion 117 membrane had a maximum current density of 120.23 mA m?2 and power density of 3486.73 mW m?2.  相似文献   

20.
Zircon SHRIMP U–Pb and in-situ Lu–Hf isotopic analyses via laser ablation microprobe-inductively coupled plasma mass spectrometer (LAM-ICPMS) of a tuff within the Upper Paleozoic from Western Beijing were carried out to give new constraints on volcano eruption ages and source area of the tuffs within the North China block (NCB). SHRIMP U–Pb zircon dating of the tuff yielded a 206Pb/238U weighted mean age of 296 ± 4 Ma (95% confidence, MSWD = 3.3), which is very similar to the emplacement age of the newly discovered Carboniferous calc-alkaline, I-type continental arc granitoid plutons in the Inner Mongolia Paleo-uplift (IMPU) on the northern margin of the NCB. In-situ Lu–Hf analysis results of most zircons from the tuff yielded initial 176Hf/177Hf ratios from 0.282142 to 0.282284 and εHf(t) values from − 15.9 to − 10.7. These Lu–Hf isotopic compositions are very similar to those of the Late Carboniferous granitoids in the IMPU, but are very different to those of the Central Asian Orogenic Belt (CAOB). Together with the sedimentary and tectonic analyses results, we inferred that the source area of the tuffs within the NCB is the IMPU instead of the CAOB. Therefore, some arc volcanoes once existed in the IMPU on northern margin of the NCB during the Late Carboniferous, but they were entirely eroded due to strong exhumation and erosion of the IMPU during the Late Carboniferous to Early Jurassic.  相似文献   

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