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1.
In the current study the application of organo‐modified bentonite for the adsorption of mycotoxins (aflatoxin B1, citrinin, patulin, and zearalenone) is presented. The modification of clays is carried out using benzyl‐tri‐n‐butyl ammonium bromide (BTB), benzethonium chloride (BTC), and dioctyl sodium sulfosuccinate (DSS). Various experimental parameters such as pH, time, adsorbent dose, and mycotoxins concentration are thoroughly studied. The modified clays (B‐BTB, B‐BTC and B‐DSS) are characterized by X‐ray fluorescence, X‐ray diffraction, and Fourier transform infrared spectroscopy. The results depicted the high detoxification efficiency (≈99%) of modified clays for the removal of mycotoxins under optimized conditions (pH 5, time: 30 min, adsorbent amount: 50 mg). The adsorption capacities of modified clays are found in the order of: B‐BTC (AFB1: 18.02, CIT: 18.35, PAT: 18.21, ZEA: 18.09 mg g?1) > B‐BTB (AFB1: 17.7, CIT: 18.11, PAT: 17.95, ZEA: 17.90 mg g?1) > B‐DSS (AFB1: 17.5, CIT: 18.02, PAT: 17.86, ZEA: 17.80 mg g?1). The obtained results fitted well with thermodynamic, isothermal (Langmuir) and pseudo‐second order kinetics. Low cost organo‐modified bentonite shows the promise in mitigating mycotoxin contamination, which could improve food safety and reduce environmental contamination.  相似文献   

2.
This study investigates structural and adsorption properties of the powdered waste shells of Rapana gastropod and their use as a new cheap adsorbent to remove reactive dye Brilliant Red HE‐3B from aqueous solutions under batch conditions. For the powder shells characterization, solubility tests in acidic solutions and X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform IR spectroscopy (FT‐IR) and thermogravimetric analyses were performed. The results revealed that the adsorbent surface is heterogeneous consisting mainly from calcium carbonate layers (either calcite or aragonite) and a small amount of organic macromolecules (proteins and polysaccharides). The dye adsorptive potential of gastropod shells powder was evaluated as function of initial solution pH (1–5), adsorbent dose (6–40 g L?1), dye concentration (50–300 mg L?1), temperature (5–60°C), and contact time (0–24 h). It was observed that the maximum values of dye percentage removal were obtained at the initial pH of solution 1.2, shells dose of 40 g L?1, dye initial concentration of 50–50 mg L?1 and higher temperatures; the equilibrium time decreases with increasing of dye concentration. It is proved that the waste seashell powder can be used as low cost bioinorganic adsorbent for dyes removal from textile wastewaters.  相似文献   

3.
Recent studies have indicated that a significant amount of iron in MgSiO3 perovskite (Pv) is Fe3+ (Fe3+/ΣFe = 10–60%) due to crystal chemistry effects at high pressure (P) and that Fe3+ is more likely than Fe2+ to undergo a high-spin (HS) to low-spin (LS) transition in Pv in the mantle. We have measured synchrotron Mössbauer spectroscopy (SMS), X-ray emission spectroscopy (XES), and X-ray diffraction (XRD) of Pv with all iron in Fe3+ in the laser-heated diamond-anvil cell to over 100 GPa. Fe3+ increases the anisotropy of the Pv unit cell, whereas Fe2+ decreases it. In Pv synthesized above 50 GPa, Fe3+ enters into both the dodecahedral (A) and octahedral (B) sites approximately equally, suggesting charge coupled substitution. Combining SMS and XES, we found that the LS population in the B site gradually increases with pressure up to 50–60 GPa where all Fe3+ in the B site becomes LS, while Fe3+ in the A site remains HS to at least 136 GPa. Fe3+ makes Pv more compressible than Mg-endmember below 50 GPa because of the gradual spin transition in the B site together with lattice compression. The completion of the spin transition at 50–60 GPa increases bulk modulus with no associated change in density. This elasticity change can be a useful seismic probe for investigating compositional heterogeneities associated with Fe3+.  相似文献   

4.
The adsorption of Cu(II) onto HCl treated rubber leaf powder (HHBL) was investigated in batch and column studies. The adsorbent was characterized by spectroscopic and quantitative analyses in order to understand the mechanism of copper adsorption. HHBL is mesoporous in nature as indicated by Bruneuer, Emmett and Teller (BET) analysis, and has various kinds of functional groups such as Si‐OH, ROH, RCOOH, RCOO–, RNH2, C‐O‐C and aromatic rings as detected by Fourier transform infrared (FTIR) spectroscopy. Copper adsorption was confirmed by scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS). The equilibrium process was described well by the Langmuir isotherm model, and a maximum adsorption capacity of 8.39 mg/g was recorded for the smallest adsorbent size (<180 μm). The two main adsorption mechanisms involved were ion exchange and complexation. The fixed bed column study demonstrated satisfactory applicability of HHBL in removing Cu(II) from aqueous solutions.  相似文献   

5.
We investigated the concentration and site occupation of ferric iron (Fe3+) in (Mg,Fe)O to understand the influence of point defects on transport properties such as atomic diffusion, electrical conductivity and viscosity. We conducted Mössbauer spectroscopy of (Mg0.8Fe0.2)O single crystals synthesized at temperatures from 1673 to 2273 K and pressures from 5 to 15 GPa with Re–ReO2 and Mo–MoO2 oxygen fugacity buffers. The isomer shift of the Mössbauer spectra suggests that Fe3+ occupies mostly the tetrahedral site at reduced conditions and both the octahedral and tetrahedral sites at oxidized conditions. We formulate a thermodynamic model of point defect dissolution in (Mg,Fe)O which suggests that unassociated tetrahedral Fe3+ is more stable than unassociated octahedral Fe3+ at high-pressure and low oxygen fugacity due to the effect of configurational entropy. The pressure dependence of Fe3+ concentration indicates a change in the dominant site occupancy of Fe3+: (1) Fe3+ in the tetrahedral site, (2) Fe3+ in the octahedral site, and (3) defect clusters of Fe3+ and cation vacancy, in the order of increasing oxygen fugacity and decreasing pressure. This is in reasonable agreement with previously reported experiments on Fe3+ concentration, Mg–Fe interdiffusivity and electrical conductivity. We consider it plausible that (Mg,Fe)O accommodates Fe3+ in the tetrahedral site down to the lower mantle. Based on our results and available experimental data, we discuss the solubility competition between Fe3+ and protons (H+), and its implications for transport properties in the lower mantle.  相似文献   

6.
The removal of Malachite green (MG) from aqueous solutions by cross‐linked chitosan coated bentonite (CCB) beads was investigated and the CCB beads were characterized by Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and X‐ray diffraction (XRD) analysis. Solubility and swelling tests were performed in order to determine the stability of the CCB beads in acidic solution, basic solution and distilled water. The amount of MG adsorbed was shown to be influenced by the initial pH of the solution, contact time and the initial MG concentration. A kinetic study indicated that a pseudo‐second‐order model agreed well with the experimental data. From the Langmuir isotherm model, the maximum adsorption capacity of MG was found to be 435.0 mg g–1. Desorption tests were carried out at different concentrations of EDTA, H2SO4 and NaOH. However, all desorbing solutions showed zero recovery of MG at all concentrations.  相似文献   

7.
This study investigates the influence of Ca2+ and Mg2+ on the removal of F? by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F? concentration decreased from 3.5 to 3.31 mg L?1 in a single (F?) system and to 1.45 mg L?1 in a ternary system (F?, Ca2+, and Mg2+) after 1 min, respectively. Thus, the F? removal efficiencies are found to increase by about 53% with the co‐active effect of Ca2+ and Mg2+ in the solution. Moreover, Ca2+ and Mg2+ are almost completely removed in the F?, Ca2+, and Mg2+ system. According to the pseudo‐first‐order modeling, the rate constants k for F?, Ca2+, and Mg2+ are 0.00348, 0.0106, and 0.0159 min?1 respectively; thus, Mg2+ > Ca2+ > F?. In the ternary system, the removal efficiencies are 53.29–66.03% for F?, 99.99–100% for Ca2+, and 87.21–95.19% for Mg2+ with initial pH 5–10. The removal efficiencies of F? increases with increases in initial concentrations of F?, Ca2+, and Mg2+. The removal of F? is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca3(PO4)2, CaHPO4, Mg3(PO4)2, and Mg(OH)2.  相似文献   

8.
A magnetic‐sulfonic graphene nanocomposite (G‐SO3H/Fe3O4) was synthesized and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. It was used for removal of three cationic dyes: safranine T (ST), neutral red (NR), victoria blue (VB), and three anionic dyes: methyl orange, brilliant yellow, and alizarin red, from environmental water. The experimental conditions were optimized, including pH, amount of adsorbent, adsorption kinetics, adsorption isotherms, ionic strength, etc. The results show that G‐SO3H/Fe3O4 can adsorb cationic dyes more efficiently and selectively than anionic dyes at pH 6.0. In the first 10 min of adsorption time, more than 93% of the cationic dyes were removed by the sorbent. Adsorption kinetics follow the pseudo‐second‐order kinetic model well. The adsorption isotherm coincided with Langmuir and Freundlich adsorption models. The maximum adsorption capacities of G‐SO3H/Fe3O4 for ST, NR, and VB dyes were 199.3, 216.8, and 200.6 mg g?1. The adsorbed cationic dyes were eluted by using different pH values of ethanol as the solvent. The established method was simple, sensitive, and rapid, and was suitable for the adsorption of cationic dyes in environmental water.  相似文献   

9.
Magnetic hydroxyapatite (HAP), which combined superparamagnetic Fe3O4 nanoparticles and HAP, composite materials were prepared by ultrasound method in this paper. It has also been found that these materials have the ability to adsorb phenol in wastewater. The magnetic materials were investigated by scanning electron microscope, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, thermal gravimetric analysis, vibrating sample magnetometer, and N2 adsorption in order to elucidate the morphology, structure, and other properties. When the prepared magnetic materials were calcined at 200°C, the prepared Fe3O4 was oxidized to Fe2O3, possessing loose‐shaped holes with a high specific area of 325.2 m2/g, a magnetization intensity of 12.5 emu/g, and the N2 adsorption isotherm belongs to porous adsorption type I. Moreover, the magnetic HAP can adsorb 90% phenol in wastewater. This means that it is an excellent recyclable phenol sorbent for sewage treatment. Experiments confirmed that the Freundlich adsorption isotherms model applies to lower phenol concentrations (0–50 mg/L), while for high phenol concentrations (50–500 mg/L) the Langmuir adsorption isotherms model fits. The magnetic sorbents have the capacity to regenerate after reaching adsorption saturation using ethanol as eluant and external magnetic field as separation unit. The efficiency of adsorption was reduced only by 10% over a six time use period.  相似文献   

10.
The Niyasar plutonic complex, one of the Cenozoic magmatic assemblages in the Urumieh‐Dokhtar magmatic belt, was the subject of detailed petrographic and mineralogical investigations. The Niyasar magmatic complex is composed of Eocene to Oligocene mafic rocks and Miocene granitoids. Eleven samples, representing the major rock units in the Niyasar magmatic complex and contact aureole were chosen for mineral chemical studies and for estimation of the pressure, temperature, and oxygen fugacity conditions of mineral crystallization during emplacement of various magmatic bodies. The analyzed samples are composed of varying proportions of quartz, plagioclase, K‐feldspar, hornblende, biotite, titanite, magnetite, apatite, zircon, garnet, and clinopyroxene. Application of the Al‐in‐hornblende barometer indicates pressures of around 0.2 to 0.4 kbar for the Eocene–Oligocene mafic bodies and around 0.5 to 1.7 kbar for the Miocene granitoids. Hornblende‐plagioclase thermometry yields relatively low temperatures (661–780 °C), which probably reflect late stage re‐equilibration of these minerals. The assemblage titanite–magnetite–quartz as well as hornblende composition were used to constrain the oxygen fugacity and H2O content during the crystallization of the parent magmas in the Miocene plutons. The results show that the Miocene granitoids crystallized from magmas with relatively high oxygen fugacity and high H2O content (~5 wt% H2O). The Miocene granitoids show similar range of oxygen fugacity, H2O contents and mineral chemical compositions, which indicate a common source for their magmas. Although the crystallization pressures of the Miocene plutons discriminate various categories of plutonic bodies emplaced at depths of about 5.7–6.5 km (Marfioun pluton), about 4.2 km (Ghalhar pluton) and 1.9–2.3 km (Poudalg pluton), they were later uplifted to the same level by vertical displacement of faults. The emplacement depths of the Niyasar plutons suggest that the central part of the Urumieh‐Dokhtar magmatic belt has experienced an uplift rate of ca. 0.25–0.4 mm/yr from the Miocene onwards.  相似文献   

11.
Han-Lin  Chen  Zi-Long  Li  Shu-Feng  Yang  Chuan-Wan  Dong  Wen-Jiao  Xiao  Yoshiaki  Tainosho 《Island Arc》2006,15(1):210-222
Abstract A mafic granulite body was newly discovered in the Altay Orogenic Belt, northwest China. The rocks comprise a suite of coarse‐grained and fine‐grained granulites. Orthopyroxenes (hypersthenes) in the rocks have high XMg and low Al2O3 contents, whereas clinopyroxenes have low TiO2 and Al2O3 contents. Amphiboles and biotites have a high Mg/(Mg + Fe2+) ratio and low contents of F and Cl. The peak metamorphic pressure–temperature (P–T) conditions are estimated as 750–780°C and 6–7 kbar, and retrograde P–T conditions are in the range of 590–620°C and 2.3–3.7 kbar, indicating significant decompression. Metamorphic reactions and P–T estimates define a clockwise P–T path. Geochemically, the rocks are high in Mg/(Mg + Fe) and Al2O3, depleted in U, Th, K and Rb, and characterized by light rare earth element enrichment and a weak positive Eu anomaly. The Altay mafic granulite shows depleted Nb, P and Ti contents in the mid‐oceanic ridge basalt normalized spider diagram. The geochemical characteristics suggest that the protolith of the Altay mafic granulite was calc‐alkaline basalt and andesite with an island‐arc affinity. The rock has a high 143Nd/144Nd ratio with ?Nd(0) > 0, indicating derivation from a mantle‐depleted source. In the present study, a two‐stage model for the evolution of the Altay mafic granulite is proposed: an early stage in which calc‐alkaline basalt and andesite with island‐arc affinity were subducted into a deeper level of the crust and subjected to granulite‐facies metamorphism generating the mafic granulite, followed by the later stage exhumation of the system into the upper crust by the late Paleozoic thrusting.  相似文献   

12.
Hydrogeochemical investigations along an E–W transect in the middle Meghna basin show groundwater chemistry and redox condition vary considerably with the change in geology. Groundwater in the Holocene shallow (<150 m bgl) alluvial aquifer in western part of the transect is affected by high arsenic concentration (As > 10 μg/l) and salinity. On the other hand, groundwater from the Pliocene Dupi Tila sandy aquifer in the eastern part is fresh and low in As (<10 μg/l). The Holocene shallow aquifers are high in dissolved As, , Fe and dissolved organic carbon (DOC), but generally low in and . High concentrations (250–716 mg/l) together with high DOC concentrations (1.4–21.7 mg/l) in these aquifers reflect active sources of degradable natural organic matter that drives the biogeochemical process. There is generally de-coupling of As from other redox-sensitive elements. In contrast, the Pliocene aquifers are low in As, and DOC. Molar ratio of /H4SiO4 suggests that silicate weathering is dominant in the deeper Holocene aquifers and in the Pliocene aquifers. Molar ratios of Cl−/ and Na+/Cl− suggest mixing of relict seawater with the fresh water as the origin of groundwater salinity. Speciation calculations show that saturation indices for siderite and rhodochrosite vary significantly between the Holocene and Pliocene aquifers. Stable isotopes (δ2H and δ18O) in groundwater indicate rapid infiltration without significant effects of evaporation. The isotopic data also indicates groundwater recharge from monsoonal precipitation with some impact of altitude effect at the base of the Tripura Hills in the east. The results of the study clearly indicate geological control (i.e. change in lithofacies) on groundwater chemistry and distribution of redox-sensitive elements such as As along the transect.  相似文献   

13.
The Hakusan volcano, central Japan, is located in a region where two subducting plates (the Pacific Plate and the Philippine Sea Plate) overlap near the junction of four plates adjacent to the Japanese Islands (the Pacific Plate, the Philippine Sea Plate, the Eurasia Plate, and the North American Plate). The Hakusan volcano consists of products from four major volcanic episodes: Kagamuro, Ko‐hakusan, and Shin‐Hakusan I and II. To date the eruption events of the Hakusan volcano we applied thermoluminescence and fission track methods. 238U(234U)–230Th disequilibrium and 206Pb/238U methods were applied to date the zircon crystallization ages for estimating the magma residence time before the eruptions. The eruption ages we obtained are ca 250 ka for Kagamuro, ca 100 ka and ca 60 ka for Ko‐Hakusan, ca 50 ka for Shin‐Hakusan I, and <10 ka for Shin‐Hakusan II. They are concordant with previous reports based on K–Ar dating. Some of the pyroclastic rocks, possibly originating from Shin‐Hakusan II activities, are dated to be ca 36 ka or 50 ka, and belong to the Shin‐Hakusan I activity. The zircon crystallization ages show several clusters prior to eruption. The magma residence time was estimated for each volcanic activity by comparing the major crystallization events and eruption ages, and we found a gradual decrease from ca. 500 ky for the Kagamuro activity to ca. 5 ky for the Shin‐Hakusan II activity. This decrease in residence time may be responsible for the decrease in volume of erupted material estimated from the current topography of the region. The scale of volcanic activity, which was deduced from the number of crystallized zircons, is more or less constant throughout the Hakusan volcanic activity. Therefore, the decrease in magma residence time is most likely the result of stress field change.  相似文献   

14.
Whole‐rock geochemical and Sr–Nd isotopic data are presented for late Miocene volcanic rocks associated with the Chah Zard epithermal Au–Ag deposit in the Urumieh‐Dokhtar Magmatic Arc (UDMA), Iran, to investigate the magma source, petrogenesis and the geodynamic evolution of the study area. The Chah Zard andesitic to rhyolitic volcanic rocks are characterized by significant Large Ion Lithophile Element (LILE) and Light Rare Earth Element (LREE) enrichment coupled with High Field Strength Element (HFSE) depletion. Our geochemical data indicate an adakitic‐like signature for the volcanic rocks (e.g. SiO2 > 62 wt%, Al2O3 > 15 wt%, MgO < 1.5 wt%, Sr/Y > 70, La/Yb > 35, Yb < 1 ppm, and Y < 18 ppm, and no significant Eu anomalies), distinguishing them from the other volcanic rocks of the UDMA. The Chah Zard volcanic rocks have similar Sr and Nd isotopic compositions; the 87Sr/86Sr(i) ratios range from 0.704 902 to 0.705 093 and the εNd(i) values are from +2.33 to +2.70. However, the rhyolite porphyry represents the final stage of magmatism in the area and has a relatively high 87Sr/86Sr ratio (0.705 811). Our data suggest that the andesitic magmas are from a heterogeneous source and likely to result from partial melting of a metasomatized mantle wedge associated with a mixture of subducted oceanic crust and sediment. These melts subsequently underwent fractional crystallization along with minor amounts of crustal assimilation. Our study is consistent with the model that the volcanic host rocks to epithermal gold mineralization in the UDMA are genetically related to late Miocene Neo‐Tethyan slab break‐off beneath Central Iran.  相似文献   

15.
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16.
Ti‐SBA‐15 materials with Ti incorporated into the framework of SBA‐15 and controllable Ti contents were successfully prepared via a post‐treatment route in supercritical CO2‐ethanol solution, followed by calcination. The resultant Ti‐SBA‐15 materials were characterized by means of different techniques including X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, IR analysis, and N2 sorption analysis. It was demonstrated that the resultant materials retained a structure similar to that of the parent SBA‐15, and Ti was incorporated into the framework of SBA‐15. At high Ti content, i.e, Si/Ti = 5:1, a TiO2 phase formed and was coated onto the inner surface of SBA‐15 in addition to the incorporation of the Ti in the framework. The BET surface areas of the Ti‐SBA‐15 samples decreased with increasing Ti content. The presence of small amounts of H2O in the reaction medium may have resulted in some TiO2 nanoparticles being uniformly distributed in the pores of the SBA‐15 accompanying the incorporation of Ti in the SBA‐15 framework.  相似文献   

17.
Ag‐modified TiO2 nanotube arrays (Ag/TiO2 NAs) were prepared and employed as a photocatalyst for degradation of 17α‐ethinylestradiol (EE2) and inactivation of Escherichia coli. The as‐synthesized Ag/TiO2 NAs were characterized by field‐emission scanning electron microscope (FESEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). It was found that metallic Ag nanoparticles were firmly deposited on the TiO2 NAs with the pore diameter of 100 nm and the length of 550 nm. Photocatalytic degradation of EE2 and inactivation of E. coli were enhanced effectively in an analogical trend using Ag/TiO2 NAs. In particular, Ag/TiO2 NAs exhibited the antimicrobial activity even in the absence of light. The Ag acted as a disinfection agent as well as the dopant of the modified TiO2 NAs photocatalysis by forming a Schottky barrier on the surface of TiO2 NAs. Inorganic ions suppressed the rates of photocatalytic degradation of EE2, with HCO having a more pronounced effect than NO or SO. Humic acid (HA) was found to increase the rate of EE2 degradation.  相似文献   

18.
The density, and therefore the pressure, of CO2 fluid inclusions in minerals can be estimated from the Fermi diad splitting of Raman spectra of CO2. An accurate determination of the pressure of CO2 fluid inclusions enables the estimation of the depth origin of rocks from the deep Earth. A micro-Raman densimeter was applied to ultramafic–mafic xenoliths sampled along the Ohku coast of Oki-Dogo Island in the Sea of Japan (East Sea). The density of CO2 fluid inclusions in the mafic granulite was 1.02–1.05 g/cm3, while those of lherzolites were 0.98–1.02 g/cm3. In contrast, the density of CO2 fluid inclusions measured in olivine gabbro, clinopyroxenite, and harzburgite were lower ranging from 0.86–to 0.99 g/cm3. Taking into account the temperature condition estimated using a pyroxene thermometer, the mafic granulite originated from a depth of 27–30 km and the lherzolites from 25–29 km. The overlapping depth of 27–29 km can be interpreted as the depth including the Moho discontinuity under Oki-Dogo Island 3.3 Ma. This estimation is consistent with geophysical observations.  相似文献   

19.
The adsorption of three cationic dyes (rhodamine B, RB; crystal violet, CV; and malachite green, MG) onto termite feces, a low‐cost adsorbent, was investigated. The adsorbent was characterized by IR spectroscopy, point of zero charge measurement, and the Boehm titration method. The adsorption follows the pseudo‐second‐order kinetic model and the Langmuir–Freundlich isotherm with maximum adsorption capacities of 95.53 mg g?1 (RB), 75.71 mg g?1 (CV), and 44.78 mg g?1 (MG). The study of thermodynamics showed that the adsorption is a spontaneous and endothermic process. This works suggest that termite feces can be used as a new low‐cost adsorbent for cationic dye removal.  相似文献   

20.
Na–HCO3–CO2-rich thermomineral waters issue in the N of Portugal, within the Galicia-Trás-os-Montes region, linked to a major NNE-trending fault, the so-called Penacova-Régua-Verin megalineament. Along this tectonic structure different occurrences of CO2-rich thermomineral waters are found: Chaves hot waters (67 °C) and also several cold (16.1 °C) CO2-rich waters. The δ2H and δ18O values of the thermomineral waters are similar to those of the local meteoric waters. The chemical composition of both hot and cold mineral waters suggests that water–rock reactions are mainly controlled by the amount of dissolved CO2 (g) rather than by the water temperature. Stable carbon isotope data indicate an external CO2 inorganic origin for the gas. δ13CCO2 values ranging between ? 7.2‰ and ? 5.1‰ are consistent with a two-component mixture between crustal and mantle-derived CO2. Such an assumption is supported by the 3He/4He ratios measured in the gas phase, are between 0.89 and 2.68 times the atmospheric ratio (Ra). These ratios which are higher than that those expected for a pure crustal origin (≈ 0.02 Ra), indicating that 10 to 30% of the He has originated from the upper mantle. Release of deep-seated fluids having a mantle-derived component in a region without recent volcanic activity indicates that extensive neo-tectonic structures originating during the Alpine Orogeny are still active (i.e., the Chaves Depression).  相似文献   

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