The isotopic composition of oxygen in As-oxyanions, is an isotope system which has not been inves... more The isotopic composition of oxygen in As-oxyanions, is an isotope system which has not been investigated until now, but with a strong potential in getting new insights into the circumstances and processes that led to the development of high arsenic groundwaters in many parts of the world. In general terms, the determination of the isotope composition of oxygen in aqueous As-oxyanions involves the successive pre-concentration, quantitative separation and precipitation of the respective species, followed by the actual measurement of the "18O values by high temperature reduction with graphite and continuous flow mass spectrometry. Arsenite and arsenate can be readily precipitated with AgNO3, but since in natural aquatic systems P is much in excess relative to As, phosphate will also precipitate. Therefore, a key issue in elaboration of an adequate analytical protocol is the development of a procedure for the quantitative separation of arsenite, arsenate and phosphate from low conc...
ABSTRACT The near-surface water cycle in a geologically complex area comprises very different sou... more ABSTRACT The near-surface water cycle in a geologically complex area comprises very different sources including meteoric, metamorphic and magmatic ones. Fluids from these sources can react with sedimentary, magmatic and/or metamorphic rocks at various depths. The current study reports a large number of major, minor and trace element analyses of meteoric, mineral, thermal and mine waters from a geologically well-known and variable area of about 200 × 150 km in SW Germany. The geology of this area comprises a Variscan granitic and gneissic basement overlain in parts by Triassic and Jurassic shales, sandstones and limestones. In both the basement and the sedimentary rocks, hydrothermal mineralization occurs (including Pb, Cu, As, Zn, U, Co and many others) which were mined in former times. Mineral waters, thermal waters and meteoric waters flowing through abandoned mines (mine waters) are distributed throughout the area, although the mine waters concentrate in and around the Schwarzwald.The present analyses show, that the major element composition of a particular water is determined by the type of surrounding rock (e.g., crystalline or sedimentary rocks) and the depth from which the water originates. For waters from crystalline rocks it is the origin of the water that determines whether the sample is Na–Cl dominant (deeper origin) or Ca–HCO3 dominant (shallow origin). In contrast, compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite (Ca–HCO3 dominant), halite (Na–Cl dominant) or gypsum (Ca–SO4 dominant). Major element data alone cannot, therefore, be used to trace the origin of a water. However, the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid–rock interaction processes. Accordingly, trace element analyses showed, that:−Ce anomalies can be used as an indicator for the origin of a water. Whereas surface waters have negative or strongly negative Ce anomalies, waters originating from greater depths show no or only weak negative Ce anomalies.−Eu anomalies can be used to differentiate between host rocks. Waters from gneisses display positive Eu anomalies, whereas waters from granites have negative ones. Waters from sedimentary rocks do not display any Eu anomalies.−Rb and Cs can also be indicators for the rock with which the fluid interacted: Rb and Cs correlate positively in most waters with Rb/Cs ratios of ∼2, which suggests that these waters are in equilibrium with the clay minerals in the rocks. Rb/Cs ratios >5 indicate reaction of a water with existing clay minerals, whereas Rb/Cs ratios <2 are probably related to host rock alteration and clay mineral formation.The chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements (REEs), Rb and Cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements.
Proceedings of the Pre-Congress Workshop "Natural Arsenic in Groundwater", 32nd International Geological Congress, Florence, Italy, 18-19 August 2004, 2005
Authigenic pyrite is formed in a wide range of depositional conditions, including not only typica... more Authigenic pyrite is formed in a wide range of depositional conditions, including not only typically euxinic conditions (when it can precipitate as syngenetic pyrite already in the water column), but also the anoxic part of normal marine sediments, below the water/sediment interface. We investigated the response in trace element composition of pyrite to such environmental differences in 49 pyrite separates
The isotopic composition of oxygen in As-oxyanions, is an isotope system which has not been inves... more The isotopic composition of oxygen in As-oxyanions, is an isotope system which has not been investigated until now, but with a strong potential in getting new insights into the circumstances and processes that led to the development of high arsenic groundwaters in many parts of the world. In general terms, the determination of the isotope composition of oxygen in aqueous As-oxyanions involves the successive pre-concentration, quantitative separation and precipitation of the respective species, followed by the actual measurement of the "18O values by high temperature reduction with graphite and continuous flow mass spectrometry. Arsenite and arsenate can be readily precipitated with AgNO3, but since in natural aquatic systems P is much in excess relative to As, phosphate will also precipitate. Therefore, a key issue in elaboration of an adequate analytical protocol is the development of a procedure for the quantitative separation of arsenite, arsenate and phosphate from low conc...
ABSTRACT The near-surface water cycle in a geologically complex area comprises very different sou... more ABSTRACT The near-surface water cycle in a geologically complex area comprises very different sources including meteoric, metamorphic and magmatic ones. Fluids from these sources can react with sedimentary, magmatic and/or metamorphic rocks at various depths. The current study reports a large number of major, minor and trace element analyses of meteoric, mineral, thermal and mine waters from a geologically well-known and variable area of about 200 × 150 km in SW Germany. The geology of this area comprises a Variscan granitic and gneissic basement overlain in parts by Triassic and Jurassic shales, sandstones and limestones. In both the basement and the sedimentary rocks, hydrothermal mineralization occurs (including Pb, Cu, As, Zn, U, Co and many others) which were mined in former times. Mineral waters, thermal waters and meteoric waters flowing through abandoned mines (mine waters) are distributed throughout the area, although the mine waters concentrate in and around the Schwarzwald.The present analyses show, that the major element composition of a particular water is determined by the type of surrounding rock (e.g., crystalline or sedimentary rocks) and the depth from which the water originates. For waters from crystalline rocks it is the origin of the water that determines whether the sample is Na–Cl dominant (deeper origin) or Ca–HCO3 dominant (shallow origin). In contrast, compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite (Ca–HCO3 dominant), halite (Na–Cl dominant) or gypsum (Ca–SO4 dominant). Major element data alone cannot, therefore, be used to trace the origin of a water. However, the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid–rock interaction processes. Accordingly, trace element analyses showed, that:−Ce anomalies can be used as an indicator for the origin of a water. Whereas surface waters have negative or strongly negative Ce anomalies, waters originating from greater depths show no or only weak negative Ce anomalies.−Eu anomalies can be used to differentiate between host rocks. Waters from gneisses display positive Eu anomalies, whereas waters from granites have negative ones. Waters from sedimentary rocks do not display any Eu anomalies.−Rb and Cs can also be indicators for the rock with which the fluid interacted: Rb and Cs correlate positively in most waters with Rb/Cs ratios of ∼2, which suggests that these waters are in equilibrium with the clay minerals in the rocks. Rb/Cs ratios >5 indicate reaction of a water with existing clay minerals, whereas Rb/Cs ratios <2 are probably related to host rock alteration and clay mineral formation.The chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements (REEs), Rb and Cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements.
Proceedings of the Pre-Congress Workshop "Natural Arsenic in Groundwater", 32nd International Geological Congress, Florence, Italy, 18-19 August 2004, 2005
Authigenic pyrite is formed in a wide range of depositional conditions, including not only typica... more Authigenic pyrite is formed in a wide range of depositional conditions, including not only typically euxinic conditions (when it can precipitate as syngenetic pyrite already in the water column), but also the anoxic part of normal marine sediments, below the water/sediment interface. We investigated the response in trace element composition of pyrite to such environmental differences in 49 pyrite separates
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