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  • Articles  (12)
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  • Articles  (12)
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  • Springer  (12)
  • American Geophysical Union
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  • Geosciences  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Coral reefs 19 (2000), S. 93-97 
    ISSN: 1432-0975
    Keywords: Key words Sampling ; Sediment ; Geochemistry ; Pore water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Several new techniques have been developed to allow the geochemical characterization of shallow pore waters in reefs. First, a new method was developed for using non-metallic well-points to sample pore waters from shallow depths (〈1 m) in coral reefs with unconsolidated substrates. These PVC well-points can be made faster and at less expense than well-points made of stainless steel. They also eliminate metal contamination and are free from the problems of corrosion in sea water. Additional improvements in sampling techniques maximize the spatial resolution of geochemical gradients and address the problems of atmospheric contamination associated with the sampling of dissolved gases. Data taken from Checker Reef, Oahu, Hawaii, illustrate the application of these methods.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 88 (2000), S. 764-777 
    ISSN: 1437-3262
    Keywords: Key words Neoproterozoic ; Dokhan volcanics ; Egypt ; Geochemistry ; Petrogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The Neoproterozoic Dokhan volcanics of the Fatira area in eastern Egypt comprise two main rock suites: (a) an intermediate volcanic suite, consisting of basaltic andesite, andesite, dacite, and their associated pyroclastic rocks; and (b) a felsic volcanic suite composed of rhyolite and rhyolitic tuffs. The two suites display well-defined major and trace element trends and a continuum in composition with wide ranges in SiO2 (54–76%), CaO (8.19–0.14%), MgO (6.96–0.04%), Sr (983–7 ppm), Zr (328–95 ppm), Cr (297–1 ppm), and Ni (72–1 ppm). They are enriched in LILEs (Rb, Ba, K, Th, Ce) relative to high field strength elements (Nb, Zr, P, Ti) and show strong affinity to calc-alkaline subduction-related rocks. However, their undeformed character, their emplacement temporally and spatially with post-orogenic A-type granite, and their high Zr/Y values suggest that their emplacement follow the cessation of subduction in eastern Egypt in an extensional-related within-plate setting. Major and trace element variations in the intermediate volcanics are consistent with their formation via partial melting of an enriched subcontinental lithospheric mantle source followed by a limited low-pressure fractional crystallization of olivine and pyroxene before emplacement. The LILE enrichment relative to HFSE is attributed to the inheritance of a subduction component from mantle material which constituted the mantle wedge during previous subduction events in eastern Egypt. The evolution of the whole volcanic spectrum was governed mainly by crystal/melt fractionation of amphibole, plagioclase, titanomagnetite, and apatite in the intermediate varieties and plagioclase, amphibole, biotite, Fe–Ti oxides, apatite, and zircon in the felsic varieties. At each stage of evolution, crystal fractionation was accompanied by variable degrees of crustal contamination.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 88 (2000), S. 791-802 
    ISSN: 1437-3262
    Keywords: Key words Variscan belt ; Moldanubian zone ; Black Forest ; Orthogneiss ; Zircon dating ; ¶Nd isotopes ; Geochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Single zircon U–Pb dating combined with 207Pb/206Pb ages obtained by the evaporation method constrains the emplacement of tonalitic, trondhjemitic, and granodioritic orthogneisses of the Moldanubian zone in the Black Forest between 500 and 510 Ma. Two detrital zircon populations of 1.9 and 1.6 Ga indicate Early-Middle Proterozoic material in the former setting of the basement. The initial eNd values range from –0.1 to –3.4 and mean crustal residence ages of 1.0–1.4 Ga are consistent with involvement of Early-Middle Proterozoic crust, and a subordinate juvenile component probably originating from subduction-related melting of the mantle. The orthogneisses have fractionated REE patterns and slightly higher K2O/Na2O ratios than typical low-K tonalite–trondhjemite–granite suites. The chemical data are interpreted as evidence for melting of amphibolite and contributions from evolved crust. The emplacement of the orthogneisses was superceded by a high-temperature metamorphic event at ∼480 Ma which we interpret as a result of lithospheric thinning in a marginal basin behind a Cambrian magmatic arc.
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  • 4
    ISSN: 1437-3262
    Keywords: Lithostratigraphy ; Petrology ; Geochemistry ; Sedimentology ; Sequence stratigraphy ; Late Neoproterozoic ; Lower Cambrian ; Central Iberian Zone ; Iberian Massif
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 O3, TiO2, Zr, and Nb abundances in shales from all the units, strongly suggest a gradual compositional change within this sedimentary succession. Together with the petrological data, the chemical results do not reveal any obvious coeval volcanic contribution to the sediments. On the basis of the chemical data, a comparison is made with other European zones containing detrital sediments composed of reworked crustal components.
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  • 5
    ISSN: 1437-3262
    Keywords: Karawanken pluton ; Eastern Alps ; Triassic ; Petrology ; Geochemistry ; Rb ; Sr age ; Triassic mantle ; Transtensional ; extensional tectonics ; Mesozoic rifting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
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  • 6
    ISSN: 1437-3262
    Keywords: Geochemistry ; Clay mineralogy ; Weathering ; Diagenesis ; Rhine ; Facies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 O contents, which can be attributed to the Alpine source supplying fresh, sodic plagioclase-rich material instead of the local, strongly weathered sediments. Increasing K2O/Al2O3 can be attributed to a similar decrease in degree of weathering. However, this trend is disturbed by the loss of K from clay minerals during weathering in organic-rich layers. Local high TiO2 anomalies, caused by preferential sorting and concentration, are found in most Pliocene sections, but they are absent in the Upper Pliocene and Lower Pleistocene Alpine-derived deposits. This change is probably due to a change in the energy of the fluvial system. Finally, (pyrite-) S contents drop (siderite-) Fe contents rise. Micromorphological observations indicate that the Pliocene pyrite was formed when freshwater deposits were flooded with seawater during short-term events. The decrease in S, and the increase in siderite-Fe, can be attributed to decreasing marine influence, as a result of the marine regression at the Pliocene–Pleistocene transition.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 89 (2000), S. 328-335 
    ISSN: 1437-3262
    Keywords: Key words Central European Variscides ; Brno Massif ; Metarhyolite ; Metabasite complex ; Geochemistry ; Zircon geochronology ; Cadomian ; Panafrican
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Brno Massif in Moravia, Czech Republic, is an important exposure of Precambrian basement in central Europe. It includes large volumes of Cadomian granitoids and a narrow fault-bounded zone with metagabbros, metadiorites, and metabasalts. This so-called Central Basic Belt also contains some metarhyolites; one of these was dated by means of the zircon evaporation method at 725 ±15 Ma. Chemical and isotope data show that the dated rock represents a mantle-derived magma which is cosanguinous with surrounding MORB-type metabasites. The data suggest that the Brno Massif hosts the oldest metabasite complex currently known in central Europe. Its formation apparently coincides with the main period of ocean-floor spreading and island-arc formation in the Panafrican orogens. This lends further support to the theory that the Brno Massif is a Gondwana-derived element.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 39 (2000), S. 990-1000 
    ISSN: 1432-0495
    Keywords: Key words Background ; Data distribution ; Normal distribution ; Log-normal distribution ; Geochemistry ; Environmental science ; Robust geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The term "background" is discussed and a definition is suggested to put an end to the currently unsatisfying (non-)definition of geochemical or natural background. Based on the requirements stated in the definition, several simple and robust statistical methods are applied to different data sets (n〉50) from the atmosphere, pedosphere, and biosphere in order to explore their potential for the evaluation of a useful and robust background. Compared with the original data set both the calculated distribution, based upon the lower 50% of the values, as well as a 2σ-approximation of the normalised data set lead to promising and realistic results. Both methods seem appropriate for a fast and reliable evaluation of likely upper limits of background values. Nevertheless, even this robust method is not able to present absolute and doubtlessly correct background values. True quantification of any natural or geochemical background still requires a thorough investigation and is impossible without costly expert knowledge.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 39 (2000), S. 1254-1260 
    ISSN: 1432-0495
    Keywords: Key words Mine ; Pit lake ; Geochemistry ; Remediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Pit lakes form when open-pit mining operations are discontinued and dewatering ceases. The increase in open-pit metal mining since the 1970s will lead to the formation of numerous pit lakes over the next 50 years. Many of these lakes will develop acid sulfate conditions with high levels of dissolved metals. Approaches to remediation of these conditions that have been recommended include the addition of lime or other alkaline materials and the stimulation of sulfate-reducing bacteria. However, prevention rather than remediation is probably the preferable approach. Measures to prevent oxidation of mining waste and wall rocks, including measures to fill pits quickly with water, to inhibit the activity of acidophilic sulfur-oxidizing bacteria, and to promote anoxic conditions at the lake bottoms may minimize the formation of acids and dissolved metals.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 39 (2000), S. 1334-1340 
    ISSN: 1432-0495
    Keywords: Keywords China ; Geochemistry ; River ; Sediment ; Trace metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A total of 26 geographically and hydrologically diverse sediment samples were collected from 12 major rivers in eastern China. The 〈63-μm fraction of the sediments was analysed for both total concentrations of Cu, Zn, Pb and Cd, and their associations with various geochemical phases. The geographical variations of sediment-bound trace metals can be related to the bedrock types and weathering processes in the corresponding river basins. The rivers in southern China had notably higher concentrations of trace metals in sediments because of abundant non-ferrous mineral deposits and stronger weathering process in the region. A large proportion of trace metals in these sediments was associated with iron and manganese oxides and organic matter. Relative low levels of trace metals were found in river sediments in northern China, and a significant proportion of the metals was bound to organic matter, carbonates, and the residual fraction. The sediments in the Yellow River, originating from special loess, had the lowest concentrations of trace metals. Most of the trace metals were associated with the carbonates and residual phases.
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