High resolution analysis of uranium and thorium concentration as well as U-series isotope distributions in a Neanderthal tooth from Payre (Ardèche, France) using laser ablation ICP-MS     

Rainer Grün  Maxime Aubert  Marie-Hélène Moncel 《Geochimica et cosmochimica acta》2008,72(21):5278-5290

We have mapped U (²³⁸U) and Th (²³²Th) elemental concentrations as well as U-series isotope distributions in a Neanderthal tooth from the Middle Palaeolithic site of Payre using laser ablation ICP-MS. The U-concentrations in an enamel section varied between 1 and 1500 ppb. The U-concentration maps show that U-migration through the external enamel surface is minute, the bulk of the uranium having migrated internally via the dentine into the enamel. The uranium migration and uptake is critically dependent on the mineralogical structure of the enamel. Increased U-concentrations are observed along lineaments, some of which are associated with cracks, and others may be related to intra-prismatic zones or structural weaknesses reaching from the dentine into the enamel. The uranium concentrations in the dentine vary between about 25,000 and 45,000 ppb. Our systematic mapping of U-concentration and U-series isotopes provides insight into the time domain of U-accumulation. Most of the uranium was accumulated in an early stage of burial, with some much later overprints. None of the uranium concentration and U-series profiles across the root of the tooth complied with a single stage diffusion-adsorption (D-A) model that is used for quality control in U-series dating of bones and teeth. Nevertheless, in the domains that yielded the oldest apparent U-series age estimates, U-leaching could be excluded. This means that the oldest apparent U-series ages of around 200 ka represent a minimum age for this Neanderthal specimen. This is in good agreement with independent age assessments (200-230 ka) for the archaeological layer, in which it was found.The Th elemental concentrations in the dental tissues were generally low (between about 1 and 20 ppb), and show little relationship with the nature of the tissue.  相似文献   

Application of zeolitic volcanic rocks for arsenic removal from water     

F. Ruggieri  V. Marín  D. Gimeno  J.L. Fernandez-Turiel  M. García-Valles  L. Gutierrez 《Engineering Geology》2008,101(3-4):245-250

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   

Analysis of unresolved complex mixtures of hydrocarbons extracted from Late Archean sediments by comprehensive two-dimensional gas chromatography (GC×GC)     

Gregory T. Ventura  Fabien Kenig  Christopher M. Reddy  Glenn S. Frysinger  Robert K. Nelson  Ben Van Mooy  Richard B. Gaines 《Organic Geochemistry》2008,39(7):846-867

Hydrocarbon mixtures too complex to resolve by traditional capillary gas chromatography display gas chromatograms with dramatically rising baselines or “humps” of coeluting compounds that are termed unresolved complex mixtures (UCMs). Because the constituents of UCMs are not ordinarily identified, a large amount of geochemical information is never explored. Gas chromatograms of saturated/unsaturated hydrocarbons extracted from Late Archean argillites and greywackes of the southern Abitibi Province of Ontario, Canada contain UCMs with different appearances or “topologies” relating to the intensity and retention time of the compounds comprising the UCMs. These topologies appear to have some level of stratigraphic organization, such that samples collected at any stratigraphic formation collectively are dominated by UCMs that either elute early- (within a window of C₁₅–C₂₀ n-alkanes), early- to mid- (C₁₅–C₃₀ n-alkanes), or have a broad UCM that extends through the entire retention time of the sample (from C₁₅–C₄₂ n-alkanes). Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC–MS) was used to resolve the constituents forming these various UCMs. Early- to mid-eluting UCMs are dominated by configurational isomers of alkyl-substituted and non-substituted polycyclic compounds that contain up to six rings. Late eluting UCMs are composed of C₃₆–C₄₀ mono-, bi-, and tricyclic archaeal isoprenoid diastereomers. Broad UCMs spanning the retention time of compound elution contain nearly the same compounds observed in the early-, mid-, and late-retention time UCMs. Although the origin of the polycyclic compounds is unclear, the variations in the UCM topology appear to depend on the concentration of initial compound classes that have the potential to become isomerized. Isomerization of these constituents may have resulted from hydrothermal alteration of organic matter.  相似文献   

Spurenelementgehalt der Saale – ein Vergleich der Analysenergebnisse aus den Jahren 1950 und 1996     

G. Proft  W. Schrn 《Chemie der Erde / Geochemistry》2008,68(2):221-233

Thirty four elements dissolved in water and 33 elements bound in particulate matter were analysed in the small river Saale (Thuringia, Germany, MQ=23 m³/s) in 1996 and the results were compared with those obtained in 1950 (44 elements). Monthly sampling was used to eliminate fluctuations caused by seasons and weather. Comparison of the element contents of a river over a 40-year-time span provides interesting insight into the anthropogenic change in the catchment area of the river with regard to „global change”.Without taking into consideration systematic errors, the analysed elements can be divided into three groups:

(a) Elements whose average annual analytical values in 1996 were lower by >50% than those in 1950: Al, As, Ba, Fe, Pb, Zn (in solution), and As, B, Cr, Li, Mn, Pb, Se, Sn, U (suspended).

(b) Elements whose average annual analytical values in 1996 are in the range of those in 1950, i.e., are within 50–150%: Ca, Co, Cr, F, K, Li, Mn, Na, Si, Sr, Ti, U (in solution), and Hg, Cr, Cu, Sc, Sr, Ti, Zn (suspended).

(c) Elements whose average annual analytical values in 1996 were higher by >150% than those in 1950: B, Cd, Mg, Ni, Rb, Sc (in solution), and Ba, Ni, P, Zr (suspended).

The increases in the element concentrations are not only caused by wastewater. Acid rain and fertilizer affect the pH and the electrolyte status of soils and cause mobilization of elements. This can be a reason for the increase in the alkalies and alkaline earth. For most elements are higher and lower values were found in 1996 and are only partly caused by systematic errors in the methods used in 1950. Taking into consideration of the natural fluctuations some element values 1996 equal or are lower (Tabelle 10 and 12). Because of the 100–200% RSD (12 samples per year), it is almost impossible to decide whether the deviations are due to analytical errors or to natural causes. The bound part of the elements is considered to be the suspended portion (seston=particulate matter) and, for one and the same element the suspended portion is equal or higher than the portion in solution. In the case of natural plant stock in the catchment area, the erosion is small. The increase in farming caused a higher soil erosion in the river. Storm precipitation causes short-term (1–2 h) peaks in the suspended load with values 2–3 orders of magnitude higher. In the case of monthly sampling, such peaks are unlikely to be detected. This produces values of suspended loads that tend to be too small. Increases of the bounded elements together with the elements in solution cause increases of eutrophication in the ocean.The contents of elements transported in solution and in particulate form in the river Saale are not equal to the element contents of the upper earth crust. Weathering and the fluviatil element transport cause a fractionation of the thallassophile (enriched in ocean) and therraphile elements (enriched in continents). Thallassophile elements are Mg, Ca, Sr, B, As, U, Sn, Cd, Zn, Se (transported in solution) and U, Cr, Li, B, Ba, Se, Mn, Cu, P, Sn, Cd, Rb, Pb, S and Zn (transported in seston) and therraphile elements are Cs, Co, Sc, Ni, Ti, Fe, Al, and K. As a result a fractionation in thallassophile and therraphile elements results and influences the geochemical cycles like magmatic differentiations.  相似文献   

Geological and environmental implications of the evaporite karst in Spain   总被引：2，自引：0，他引：2  

F. Gutiérrez  J. M. Calaforra  F. Cardona  F. Ortí  J. J. Durán  P. Garay 《Environmental Geology》2008,53(5):951-965

In Spain, evaporite outcrops cover approximately 7% of the total area of the country. Most of the evaporitic formations are made up of Ca-sulfates (gypsum/anhydrite) or Ca-sulfates and halite. Certain Paleogene marine evaporites also contain K-Mg-chlorides, and some Tertiary continental formations bear substantial amounts of Na-sulfates in the subsurface (glauberite and thenardite). Mesozoic evaporitic formations commonly wedge out towards the ground surface, passing into condensed sequences and dissolution-collapse breccias. Some of these highly porous breccias constitute major regional aquifers. In several areas, interstratal karstification of the evaporites has given rise to gravitational deformations such as basin structures, monoclines, and collapse structures covering several square kilometers that record a cumulative subsidence in excess of 200 m (Teruel and Calatayud Grabens). A widespread consequence of evaporite dissolution processes in Spain is the hydrochemical degradation of surface waters. Some of the largest and most outstanding lake systems, from an environmental perspective, occur in karstic depressions developed in evaporitic formations (Fuente de Piedra, Gallocanta, Bujaraloz, and Bañolas lakes). Sinkhole activity is a major geohazard in several evaporite karst areas. The sinkhole risk has a particularly high impact in sectors where Tertiary evaporites are overlain by Quaternary alluvial aquifers (Calatayud, Zaragoza, and Madrid areas). Some of the detrimental effects of subsidence include severe damage to historical monuments (Calatayud), the demolition of a whole village (Puilatos), or the derailment of a freight train (Zaragoza area). The deepest gypsum caves are found in Triassic diapiric structures (El Sumidor Cave, 210 m deep), and the longest ones are developed in horizontally lying Neogene sequences (Sorbas caves, and Estremera maze cave). The Cardona diapir hosts salt caves up to 4,300 m long whose genesis is related to flooding of mine galleries caused by the interception of a phreatic conduit. The main anthropogenic impacts on the endokarstic systems are related to the disposal of wastewaters and the destruction of caves by quarrying. The fluvial valleys that cross Tertiary evaporitic outcrops commonly show peculiar geological characteristics related to dissolution-induced synsedimentary subsidence phenomena: (1) Thickened alluvium filling dissolution basins up to several tens of kilometers long and more than 100 m deep. The largest thickenings are found in areas where the bedrock contains halite and glauberite. (2) Superimposed alluvial units locally bounded by angular unconformities. (3) Abundant deformational structures and paleosinkholes related to the rockhead and/or interstratal karstification of the substratum. These fluvial valleys typically are flanked by a prominent gypsum escarpment. Rock-falls favored by the dissolutional enlargement of joints derived from these scarps are the type of mass movement which has caused the highest number of casualties in Spain.  相似文献   

Development of a geotechnical and geophysical database for seismic zonation of the Ankara Basin,Turkey     

Mustafa K. Koçkar  Haluk Akgün 《Environmental Geology》2008,54(1):165-182

The Kocaeli earthquake (M _w = 7.4) of 17 August 1999 occurred in the Eastern Marmara Region of Turkey along the North Anadolu Fault and resulted in a very serious loss of life and property. One of the most important geotechnical issues of this event was the permanent ground deformations because of both liquefaction and faulting. These deformations occurred particularly along the southern shores of ?zmit Bay and Sapanca Lake between the cities of Yalova and Adapazar? in the west and east, respectively. In this study, three sites founded on delta fans, namely De?irmendere Nose, Yeniköy tea garden at Seymen on the coast of ?zmit Bay, and Vak?f Hotel site on the coast of Sapanca Lake were selected as typical cases. The main causes of the ground deformations at these sites were then investigated. Geotechnical characterization of the ground, derivation of displacement vectors from the pre- and post-earthquake aerial photographs, liquefaction assessments based on field performance data, and analyses carried out using the sliding body method have been fundamental in this study. The displacement vectors determined from photogrammetric evaluations conducted at De?irmendere and Seymen showed a combined movement of faulting and liquefaction. But except the movements in the close vicinity of shorelines, the dominant factor in this movement was faulting. The results obtained from the analyses suggested that the ground failure at De?irmendere was a submarine landslide mainly because of earthquake shaking rather than liquefaction. On the other hand, the ground failures at the Yeniköy tea garden on the coast of Seymen and the hotel area in Sapanca town resulted from liquefaction-induced lateral spreading. It was also obtained that the ground deformations estimated from the sliding body method were quite close to those measured by aerial photogrammetry technique.  相似文献   

A comparison of winter mercury accumulation at forested and no-canopy sites measured with different snow sampling techniques     

Sarah J. Nelson  Kenneth B. Johnson  Kathleen C. Weathers  Cynthia S. Loftin  Ivan J. Fernandez  Jeffrey S. Kahl  David P. Krabbenhoft 《Applied Geochemistry》2008

Atmospheric mercury (Hg) is delivered to ecosystems via rain, snow, cloud/fog, and dry deposition. The importance of snow, especially snow that has passed through the forest canopy (throughfall), in delivering Hg to terrestrial ecosystems has received little attention in the literature. The snowpack is a dynamic system that links atmospheric deposition and ecosystem cycling through deposition and emission of deposited Hg. To examine the magnitude of Hg delivery via snowfall, and to illuminate processes affecting Hg flux to catchments during winter (cold season), Hg in snow in no-canopy areas and under forest canopies measured with four collection methods were compared: (1) Hg in wet precipitation as measured by the Mercury Deposition Network (MDN) for the site in Acadia National Park, Maine, USA, (2) event throughfall (collected after snowfall cessation for accumulations of >8 cm), (3) season-long throughfall collected using the same apparatus for event sampling but deployed for the entire cold season, and (4) snowpack sampling. Estimates (mean ± SE) of Hg deposition using these methods during the 91-day cold season in 2004–2005 at conifer sites showed that season-long throughfall Hg flux (1.80 μg/m²) < snowpack Hg (2.38 ± 0.68 μg/m²) < event throughfall flux (5.63 ± 0.38 μg/m²). Mercury deposition at the MDN site (0.91 μg/m²) was similar to that measured at other no-canopy sites in the area using the other methods, but was 3.4 times less than was measured under conifer canopies using the event sampling regime. This indicates that snow accumulated under the forest canopy received Hg from the overstory or exhibited less re-emission of Hg deposited in snow relative to open areas. The soil surface of field-scale plots were sprayed with a natural rain water sample that contained an Hg tracer (²⁰²Hg) just prior to the first snowfall to explore whether some snowpack Hg might be explained from soil emissions. The appearance of the ²⁰²Hg tracer in the snowpack (0–64% of the total Hg mass in the snowpack) suggests that movement of Hg from the soil into the snowpack is possible. However, as with any tracer study the ²⁰²Hg tracer may not precisely represent the reactivity and mobility of natural Hg in soils.  相似文献   

Dissolution of arsenopyrite (FeAsS) and galena (PbS) in the presence of desferrioxamine-B at pH 5     

Hilda Cornejo-Garrido  Pilar Fernández-Lomelín  Javiera Cervini-Silva 《Geochimica et cosmochimica acta》2008,72(12):2754-2766

Microorganisms and higher plants produce biogenic ligands, such as siderophores, to mobilize Fe that otherwise would be unavailable. In this paper, we study the stability of arsenopyrite (FeAsS), one of the most important natural sources of arsenic on Earth, in the presence of desferrioxamine (DFO-B), a common siderophore ligand, at pH 5. Arsenopyrite specimens from mines in Panasqueira, Portugal (100-149 μm) that contained incrustations of Pb, corresponding to elemental Pb as determined by scanning electron microscopy-electron diffraction spectroscopy (SEM-EDX), were used for this study. Batch dissolution experiments of arsenopyrite (1 g L⁻¹) in the presence of 200 μM DFO-B at initial pH (pH₀) 5 were conducted for 110 h. In the presence of DFO-B, release of Fe, As, and Pb showed positive trends with time; less dependency was observed for the release of Fe, As, and Pb in the presence of only water under similar experimental conditions. Detected concentrations of soluble Fe, As, and Pb in suspensions containing only water were found to be ca. 0.09 ± 0.004, 0.15 ± 0.003, and 0.01 ± 0.01 ppm, respectively. In contrast, concentrations of soluble Fe, As, and Pb in suspensions containing DFO-B were found to be 0.4 ± 0.006, 0.27 ± 0.009, and 0.14 ± 0.005 ppm, respectively. Notably, the effectiveness of DFO-B for releasing Pb was ca. 10 times higher than that for releasing Fe. These results cannot be accounted for by thermodynamic considerations, namely, by size-to-charge ratio considerations of metal complexation by DFO-B. As determined by SEM-EDX, elemental sample enrichment analysis supports the idea that the Fe-S subunit bond energy is limiting for Fe release. Likely, the mechanism(s) of dissolution for Pb incrustations is independent and occurs concurrently to that for Fe and As. Our results show that dissolution of arsenopyrite leads to precipitation of elemental sulfur, and is consistent with a non-enzymatic mineral dissolution pathway. Finally, speciation analyses for As indicate variability in the As(III)/As(V) ratio with time, regardless of the presence of DFO-B or water. At reaction times <30 h, As(V) concentrations were found to be 50-70%, regardless of the presence of DFO-B. These results are interpreted to indicate that transformations of As are not imposed by ligand-mediated mechanisms. Experiments were also conducted to study the dissolution behavior of galena (PbS) in the presence of 200 μM at pH₀ 5. Results show that, unlike arsenopyrite, the dissolution behavior of galena shows coupled increases in pH with decreases in metal solubility at t > 80 h. Oxidative dissolution mechanisms conveying sulfur oxidation bring about the production of {H⁺}. However, dissolution data trends for arsenopyrite and galena indicate {H⁺} consumption. It is plausible that the formation of Pb species is dependent on {H⁺} and {OH⁻}, namely, stable surface hydroxyl complexes of the form (pH₅₀ 5.8) and for pH values 5.8 or above.  相似文献   

Facies analyses and volcanic setting of the giant Neves Corvo massive sulfide deposit,Iberian Pyrite Belt,Portugal     

Carlos J. P. Rosa  Jocelyn McPhie  Jorge M. R. S. Relvas  Zélia Pereira  Tomás Oliveira  Nelson Pacheco 《Mineralium Deposita》2008,43(4):449-466

In the Iberian Pyrite Belt, volcanic rocks are relatively scarce, accounting for approximately only 25% of the geologic record, with the remaining 75% consisting of sedimentary units. This association is very clear in the host succession to the Neves Corvo massive sulfide deposit in Portugal. The Neves Corvo host succession comprises the products of explosive and effusive rhyolitic eruptions intercalated with mudstone that records a submarine below-wave-base environment and provides precise biostratigraphic age constraints. The first and second volcanic events involved eruptions at local intrabasinal vents. The first event generated thick beds of fiamme breccia that are late Famennian in age. The fiamme were originally pumice clasts produced by explosive eruptions and were subsequently compacted. The second event was the late Strunian (latest Famennian) effusion of rhyolitic lava that was pervasively quench-fragmented. The third and final event is younger than the massive sulfide deposits poorly represented in the mine area and minor compared with the two other events. The integration of biostratigraphic data with the volcanic facies architecture indicates that the Neves Corvo ore deposits are similar in age to the late Strunian rhyolitic lava. Although regionally the Iberian Pyrite Belt is essentially a sedimentary succession, ore formation at Neves Corvo can be closely linked to discrete volcanic events that produced a relatively narrow range of volcanic facies.  相似文献   

Geology,fluid inclusion and sulphur isotope characteristics of the El Cobre VHMS deposit,Southern Cuba     

Xiomara Cazañas  Pura Alfonso  Joan Carles Melgarejo  Joaquín Antonio Proenza  Anthony Edward Fallick 《Mineralium Deposita》2008,43(7):805-824

The El Cobre deposit is located in eastern Cuba within the volcanosedimentary sequence of the Sierra Maestra Paleogene arc. The deposit is hosted by tholeiitic basalts, andesites and tuffs and comprises thick stratiform barite and anhydrite bodies, three stratabound disseminated up to massive sulphide bodies produced by silicification and sulphidation of limestones or sulphates, an anhydrite stockwork and a siliceous stockwork, grading downwards to quartz veins. Sulphides are mainly pyrite, chalcopyrite and sphalerite; gold occurs in the stratabound ores. Fluid inclusions measured in sphalerite, quartz, anhydrite and calcite show salinities between 2.3 and 5.7 wt% NaCl eq. and homogenisation temperatures between 177 and 300°C. Sulphides from the stratabound mineralisation display δ ³⁴S values of 0‰ to +6.0‰, whilst those from the feeder zone lie between −1.4‰ and +7.3‰. Sulphides show an intra-grain sulphur isotope zonation of about 2‰; usually, δ ³⁴S values increase towards the rims. Sulphate sulphur has δ ³⁴S in the range of +17‰ to +21‰, except two samples with values of +5.9‰ and +7.7‰. Sulphur isotope data indicate that the thermochemical reduction of sulphate from a hydrothermal fluid of seawater origin was the main source of sulphide sulphur and that most of the sulphates precipitated by heating of seawater. The structure of the deposit, mineralogy, fluid inclusion and isotope data suggest that the deposit formed from seawater-derived fluids with probably minor supply of magmatic fluids.  相似文献