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EARTH SCIENCES (427 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (1 follower)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (2 followers)
Acta Geophysica     Hybrid Journal   (7 followers)
Acta Geotechnica     Hybrid Journal   (9 followers)
Acta Meteorologica Sinica     Hybrid Journal   (2 followers)
Advances in High Energy Physics     Open Access   (12 followers)
Advances In Physics     Hybrid Journal   (6 followers)
Aeolian Research     Hybrid Journal   (1 follower)
African Journal of Aquatic Science     Hybrid Journal   (13 followers)
Algological Studies     Full-text available via subscription   (2 followers)
Alpine Botany     Hybrid Journal   (2 followers)
AMBIO     Hybrid Journal   (13 followers)
Anales del Instituto de la Patagonia     Open Access   (2 followers)
Andean geology     Open Access   (5 followers)
Annales Henri Poincaré     Hybrid Journal   (2 followers)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (1 follower)
Annals of Geophysics     Full-text available via subscription   (9 followers)
Annals of GIS     Hybrid Journal   (15 followers)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (9 followers)
Applied Clay Science     Hybrid Journal   (2 followers)
Applied Geochemistry     Hybrid Journal   (6 followers)
Applied Geomatics     Hybrid Journal   (6 followers)
Applied Geophysics     Hybrid Journal   (6 followers)
Applied Ocean Research     Hybrid Journal   (6 followers)
Applied Petrochemical Research     Open Access   (3 followers)
Applied Remote Sensing Journal     Open Access   (5 followers)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (19 followers)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (6 followers)
Artificial Satellites     Open Access   (11 followers)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (2 followers)
Asian Journal of Earth Sciences     Open Access   (16 followers)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (3 followers)
Atmosphere-Ocean     Full-text available via subscription   (3 followers)
Atmospheric and Climate Sciences     Open Access   (14 followers)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (11 followers)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (7 followers)
Bragantia     Open Access   (2 followers)
Bulletin of Earthquake Engineering     Hybrid Journal   (9 followers)
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Bulletin of Marine Science     Full-text available via subscription   (12 followers)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (2 followers)
Bulletin of the Seismological Society of America     Full-text available via subscription   (15 followers)
Bulletin of Volcanology     Hybrid Journal   (11 followers)
Canadian Journal of Plant Science     Full-text available via subscription   (10 followers)
Canadian Mineralogist     Full-text available via subscription   (1 follower)
Canadian Water Resources Journal     Hybrid Journal   (17 followers)
Carbonates and Evaporites     Hybrid Journal   (3 followers)
CATENA     Hybrid Journal   (3 followers)
Central European Journal of Geosciences     Hybrid Journal   (5 followers)
Central European Journal of Physics     Hybrid Journal   (2 followers)
Chemical Geology     Hybrid Journal   (9 followers)
Chemie der Erde - Geochemistry     Hybrid Journal   (3 followers)
Chinese Geographical Science     Hybrid Journal   (3 followers)
Chinese Journal of Geochemistry     Hybrid Journal   (2 followers)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (3 followers)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (8 followers)
Coastal Management     Hybrid Journal   (17 followers)
Comptes Rendus Geoscience     Full-text available via subscription   (5 followers)
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Computational Mathematics and Mathematical Physics     Hybrid Journal   (2 followers)
Computers and Geotechnics     Hybrid Journal   (6 followers)
Continental Journal of Earth Sciences     Open Access   (1 follower)
Continental Shelf Research     Hybrid Journal   (6 followers)
Contributions to Mineralogy and Petrology     Hybrid Journal   (7 followers)
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Coral Reefs     Hybrid Journal   (17 followers)
Cretaceous Research     Hybrid Journal   (3 followers)
Cybergeo : European Journal of Geography     Open Access   (3 followers)
Developments in Geotectonics     Full-text available via subscription   (1 follower)
Developments in Quaternary Science     Full-text available via subscription   (3 followers)
Développement durable et territoires     Open Access   (2 followers)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (2 followers)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (3 followers)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (101 followers)
Earth Interactions     Full-text available via subscription   (7 followers)
Earth Science Research     Open Access   (5 followers)
Earth Surface Processes and Landforms     Hybrid Journal   (10 followers)
Earth System Dynamics     Open Access   (4 followers)
Earth System Dynamics Discussions     Open Access   (3 followers)
Earth's Future     Open Access   (1 follower)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (7 followers)
Earthquake Spectra     Full-text available via subscription   (11 followers)
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Ecological Questions     Open Access   (5 followers)
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Energy Efficiency     Hybrid Journal   (9 followers)
Energy Exploration & Exploitation     Full-text available via subscription   (2 followers)
Environmental Earth Sciences     Hybrid Journal   (10 followers)
Environmental Geology     Hybrid Journal   (10 followers)
Environmental Geosciences     Full-text available via subscription   (4 followers)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (1 follower)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (15 followers)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (6 followers)

        1 2 3 4 5 | Last

Chemie der Erde - Geochemistry    [5 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0009-2819
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.612]   [H-I: 23]
  • Silicate-bearing iron meteorites and their implications for the evolution
           of asteroidal parent bodies
    • Abstract: Publication date: Available online 14 January 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Alex Ruzicka
      Silicate-bearing iron meteorites differ from other iron meteorites in containing variable amounts of silicates, ranging from minor to stony-iron proportions (∼50%). These irons provide important constraints on the evolution of planetesimals and asteroids, especially with regard to the nature of metal–silicate separation and mixing. I present a review and synthesis of available data, including a compilation and interpretation of host metal trace-element compositions, oxygen-isotope compositions, textures, mineralogy, phase chemistries, and bulk compositions of silicate portions, ages of silicate and metal portions, and thermal histories. Case studies for the petrogeneses of igneous silicate lithologies from different groups are provided. Silicate-bearing irons were formed on multiple parent bodies under different conditions. The IAB/IIICD irons have silicates that are mainly chondritic in composition, but include some igneous lithologies, and were derived from a volatile-rich asteroid that underwent small amounts of silicate partial melting but larger amounts of metallic melting. A large proportion of IIE irons contain fractionated alkali-silica-rich inclusions formed as partial melts of chondrite, although other IIE irons have silicates of chondritic composition. The IIEs were derived from an H-chondrite-like asteroid that experienced more significant melting than the IAB asteroid. The two stony-iron IVAs were derived from an extensively melted and apparently chemically processed L or LL-like asteroid that also produced a metallic core. Ungrouped silicate-bearing irons were derived from seven additional asteroids. Hf–W age data imply that metal–silicate separation occurred within 0–10Ma of CAI formation for these irons, suggesting internal heating by 26Al. Chronometers were partly re-set at later times, mainly earlier for the IABs and later for the IIEs, including one late (3.60±0.15Ga) strong impact that affected the “young silicate” IIEs Watson (unfractionated silicate, and probable impact melt), Netschaëvo (unfractionated, and metamorphosed), and Kodaikanal (fractionated). Kodaikanal probably did not undergo differentiation in this late impact, but the similar ages of the “young silicate” IIEs imply that relatively undifferentiated and differentiated materials co-existed on the same asteroid. The thermal histories and petrogeneses of fractionated IIE irons and IVA stony irons are best accommodated by a model of disruption and reassembly of partly molten asteroids.

      PubDate: 2014-01-16T00:07:04Z
  • Historical mercury trends recorded in sediments from the Laguna del Plata,
           Córdoba, Argentina
    • Abstract: Publication date: Available online 7 January 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Yohana Vanesa Stupar , Jörg Schäfer , María Gabriela García , Sabine Schmidt , Eduardo Piovano , Gérard Blanc , Frédéric Huneau , Philippe Le Coustumer
      The main carrying phases of mercury (Hg) were analyzed in a 120cm sediment core taken at the Laguna del Plata (LP), a small lake connected to the main water body of Laguna Mar Chiquita (LMC) during highstands. LMC is considered to be one of the largest saline lakes in the world representing a sensitive climatic indicator due to its frequent lake level variations at millennial and interdecadal scale like the last ones that started early in the 1970s and after 2004. Total particulate Hg (HgTP) concentrations vary between ∼13 and ∼131μgkg−1 indicating a system with low pollution. Selective extractions with ascorbate, HCl and H2O2 were performed in the sediments and they revealed that Hg is associated mainly to reactive sulphides in the base of the core, while in the middle and upper part the organic matter seems to be the main Hg-bearing phase. The highest and most important peak was found in sediments accumulated between 1991 and 1995. More than a punctual source of pollution, this peak is likely related to two eruptive events occurred in the Andean Cordillera in this period: the eruption of Hudson volcano in southern Patagonia that occurred in 1991 and the one of the Láscar volcano in northern Chile that occurred in 1993. In both cases, the respective ash plumes were documented to have reached the Laguna del Plata region.

      PubDate: 2014-01-08T00:06:11Z
  • Mineral chemical constraints on the petrogenesis of mafic and intermediate
           volcanic rocks from the Erciyes and Hasandağ volcanoes, Central
    • Abstract: Publication date: Available online 18 December 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Nezihi Köprübaşi , Aykut Güçtekin , Dağhan Çelebi , M. Ziya Kirmaci
      Hasandağ and Erciyes stratovolcanoes, which produced both calc-alkaline and alkaline eruptive products, are the two important volcanic complexes in Central Anatolia. There are three geochemical evolution stages in the history of the Hasandağ strato volcanic complex: (1) Keçikalesi tholeiitic, (2) Hasandağ calc-alkaline and (3) Hasandağ alkaline. Volcanologic and petrologic characteristics of the Hasandağ and Erciyes calc-alkaline series show that water played an important role on the genesis of these rocks. These rocks are phenocryst-rich with vesicular texture, and contain hydrous mineral phases. The approximate pressure and temperature estimates obtained from the mineral chemistry studies of the Hasandağ strato volcanic complex indicate crystallization temperature of 1100°C with 2.5–3.4kbar pressure interval for the first stage of Keçikalesi tholeiitic volcanism, and about 850°C temperatures with 4.3–9.6kbar pressure intervals for the second stage of Hasandağ calc-alkaline volcanism. The geochemical evolution of Erciyes volcanic complex also exhibits three distinct evolutionary stages: (1) Koçdağ alkaline, (2) Koçdağ calc-alkaline and (3) Erciyes calc-alkaline. The temperature of Koçdağ alkaline volcanism is 1097–1181°C and in a range of 5.1–6.7kbar pressure, for Koçdağ calc-alkaline volcanism 850–1050°C temperature to 2.0–6.6kbar pressure interval, and for Erciyes calc-alkaline volcanism about 950°C temperature, to 3.2–7.9kbar pressure intervals were calculated. Polybaric origin of magma chambers for calc-alkaline and alkaline rocks and disequilibrium parameters observed in phenocrysts indicate that the rocks were affected by magma mixing processes in crustal magma chambers. The disequilibrium features of amphibole and plagioclase phenocrysts in these rocks point the latent heat in magma chambers and periodic recharging with mafic magma chambers and also show that magmas reequilibrate before the eruption.

      PubDate: 2013-12-19T00:06:15Z
  • Geochemical behavior and speciation modeling of rare earth elements in
           acid drainages at Sarcheshmeh porphyry copper deposit, Kerman Province,
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4
      Author(s): Reza Sharifi , Farid Moore , Behnam Keshavarzi
      Acid mine drainage is a major source of water pollution in the Sarcheshmeh porphyry copper mine area. The concentrations of heavy metals and rare earth elements (REEs) in the host rocks, natural waters and acid mine drainage (AMD) associated with mining and tailing impoundments are determined. Contrary to the solid samples, AMDs and impacted stream waters are enriched in middle rare earth elements (MREEs) and heavy rare earth elements (HREEs) relative to light rare earth elements (LREEs). This behavior suggests that REE probably fractionate during sulfide oxidation and acid generation and subsequent transport, so that MREE and HREE are preferentially enriched. Speciation modeling predict that the dominant dissolved REE inorganic species are Ln3+, Ln(SO4)2 −, LnSO4 +, LnHCO3 2+, Ln(CO3)2 − and LnCO3 +. Compared to natural waters, Sarcheshmeh AMD is enriched in REEs and SO4 2−. High concentrations of SO4 2− lead to the formation of stable LnSO4 +, thereby resulting in higher concentrations of REEs in AMD samples. The model indicates that LnSO4 + is the dissolved form of REE in acid waters, while carbonate and dicarbonate complexes are the most abundant dissolved REE species in alkaline waters. The speciation calculations indicate that other factors besides complexation of the REE's, such as release of MREE from dissolution and/or desorption processes in soluble salts and poorly crystalline iron oxyhydroxy sulfates as well as dissolution of host rock MREE-bearing minerals control the dissolved REE concentrations and, hence, the MREE-enriched patterns of acid mine waters.

      PubDate: 2013-11-29T00:06:04Z
  • Genesis of the Nasirabad manganese occurrence, Fars province, Iran:
           Geochemical evidences
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4
      Author(s): Alireza Zarasvandi , David Lentz , Mohsen Rezaei , Houshang Pourkaseb
      The Nasirabad manganese occurrence is located to the south of the Neyriz in the Fars province. Structurally and lithologically, this occurrence lies in the southwest part of the Zagros Thrust Belt and was deposited as Mn-nodules and interconnected ore-bearing interlayer's with radiolarite cherts in the vicinity of the Neyriz ophiolites. The present work deals with the geology and geochemistry of the Nasirabad manganese occurrence with a discussion of its genesis. High Mn/Fe (average 18.85) and high Ba (average 28,830ppm) with low Pb (2.0ppm) and LREE>HREE, La n /Nd n (average 4.5), Dy n /Yb n (average 1.2) and negative Eu anomaly suggest distal hydrothermal source. The Co/Zn (average 2.2), Ce/La ratio (average 0.67) and trace element discrimination diagrams indicate hydrothermal–hydrogenous processes. Y/Ho ratio (average 24.85) and strong positive correlation coefficient between major oxides and some high field strength elements (HFSE) like; TiO2 vs Fe2O3 (r =0.98), Al2O3 vs Zr (r =0.97), Al2O3 vs Fe2O3 (r =0.98), Zr vs K2O (r =0.98), Nb vs TiO2 (r =0.92), Th vs Fe2O3 (r =0.76), Th vs MgO (r =0.86) reveal the presence of volcaniclastics and (or) terrigenous detritals of mafic composition being deposited into the depositional basin. It seems that intermittent interlayering of mafic detrital material derived from volcanic eruption of the Neyriz island arc directly affected the physicochemical conditions of hydrothermal ore precipitation in this basin and consequently the Nasirabad manganese ores represent hydrothermal–hydrogenous geochemical characteristics. The Nasirabad is an example of non-sulphidic, oxic Mn-mineralization. Similar trend between the enrichment and depletion of some bioessential elements (e.g., Mn, As, Ba, Sr, Co, Ce) might have been resulted from selective sequestering of metal ions by microbial processes and hence hydrogenous characteristics may also be the result of biogenetic processes. Moreover the high dilution of distal hydrothermal exhalations by sea water cannot be ruled out.

      PubDate: 2013-11-29T00:06:04Z
  • Geochemistry of Silurian–Carboniferous sedimentary rocks of the
           Ulaanbaatar terrane, Hangay–Hentey belt, central Mongolia:
           Provenance, paleoweathering, tectonic setting, and relationship with the
           neighbouring Tsetserleg terrane
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4
      Author(s): Narantuya Purevjav , Barry Roser
      The Hangay–Hentey belt is situated in the central Northern Mongolia, and forms part of the Central Asian Orogenic Belt (CAOB). It is internally subdivided into seven terranes, the largest of which are the neighbouring Ulaanbaatar and Tsetserleg terranes. These coeval terranes are mainly composed of Silurian–Devonian accretionary complexes and Carboniferous turbidites. Proposals for their depositional setting range from passive margin through to island arc. A suite of 19 Ulaanbaatar terrane sandstones and mudrocks (Gorkhi and Altanovoo Formations) were collected with the aim of constraining their provenance, source weathering, and depositional setting based on whole-rock major and trace element data, and for comparison with the neighbouring Tsetserleg terrane. New REE analyses were also made of 35 samples from the Ulaanbaatar and Tsetserleg terranes. Geochemically the Ulaanbaatar sandstones are classed as wackes, and most of the mudstones as shales. Geochemical parameters suggest an immature source, similar to that of the Tsetserleg terrane. Geochemical contrasts between sandstones and mudrocks in the Ulaanbaatar sediments are small, and trends on element – Al2O3 variation diagrams are weak. Comparison with average upper continental crust (UCC), major element discriminant scores, and immobile element ratios (Th/Sc, Zr/Sc, Ce/Sc, Ti/Zr) indicate a uniform average source composition between dacite and rhyolite. Maximum Chemical Index of Alteration value in the Ulaanbaatar terrane is ∼65 after correction for K-metasomatism, indicating minimal weathering in a tectonically active source, similar to that of the Tsetserleg terrane. REE data in both terranes show moderate LREE enrichment and flat HREE segments, with negative Eu anomalies somewhat less than those in UCC and PAAS. Chondrite-normalized patterns are very similar to that for average Paleozoic felsic volcanic rock, supporting the relatively felsic source indicated by immobile trace element ratios. Tectonic setting discriminants (K2O/Na2O–SiO2/Al2O3, La–Th–Sc, Th–Sc–Zr) indicate an evolved continental island arc (CIA; A2) environment for both terranes, similar to several other CAOB suites of similar age. This common arc source was situated within the Mongol-Okhotsk Ocean during Silurian–Lower Carboniferous time. The present-day Aleutian arc is a possible modern analogue of the depositional setting.

      PubDate: 2013-11-29T00:06:04Z
  • Prediction of buried calcite dissolution in the Ordovician carbonate
           reservoir of the Tahe Oilfield, NW china: Evidence from formation water
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4
      Author(s): Zhuang Ruan , Bingsong Yu , Lidong Wang , Yinglu Pan , Guanghui Tan
      The Lower–Middle Ordovician reservoir of the Tahe Oilfield is dominated by limestones with reservoir spaces formed by the generation of dissolution pores, meaning that buried karst formation can be evaluated by studying water–rock reactions between groundwater and calcite. The hydrogeological information preserved in this reservoir indicates that the Ordovician groundwater were high-salinity and high-closure, characteristics that are of significance to water–calcite reactions. Theoretical chemical thermodynamics combined with equilibrium calcite solution ionization allowed us to establish a dissolution–precipitation evaluation model for calcite, with the theoretical activity of Ca2+ in solution ( a C a eq 2 + ) controlled by temperature, pressure, [ΣCO2]−[Ca2+] and solution pH, and with the actual activity of Ca2+ in solution (aCa2+) being controlled by the concentration of various ions in solution. Ionization reaction directions are controlled by ΔG values; these values can be calculated using a C a eq 2 + and aCa2+. Here, ground water data were collected from 34 wells that intercepted Ordovician sediments within the Tahe Oilfield, and calcite ΔG values were calculated for these wells. These data indicate that the groundwater in this oilfield favours the dissolution of limestone, with limestones in the west and south of the Tahe Oilfield being more susceptible to dissolution, consistent with observations within the oilfield. The methods employed during this study can also be used to quantitatively assess susceptibility to burial dissolution and to support reservoir evaluation.

      PubDate: 2013-11-29T00:06:04Z
  • Editorial Board
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4

      PubDate: 2013-11-29T00:06:04Z
  • Geochemistry and petrogenesis of the Ediacaran post-collisional Jabal
           Al-Hassir ring complex, Southern Arabian Shield, Saudi Arabia
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4
      Author(s): Asaad M.B. Moufti , Kamal A. Ali , Martin J. Whitehouse
      The Jabal Al-Hassir ring complex is located between latitudes 19°21′ and 19°42′N, and longitudes 42°55′ and 4312′E, Southern Arabian Shield. It is an alkaline to highly fractionated calc-alkaline granite complex consisting of an inner core of biotite granite followed outward by porphyritic sodic-calcic amphibole (ferrobarroisite) granite. U–Pb zircon geochronology indicates that the Jabal Al-Hassir ring complex was emplaced at ca. 620Ma. The granites display highly fractionated geochemical features (i.e., Eu/Eu*=0.05–0.35; enrichment of K, Rb, Th, U, Zr, Hf, Y and REE; depletion of Ta, Nb, Ba, Sr, P, Eu, and Ti). Jabal Al-Hassir granites are post-collisional plutonic rocks and contain abundant microcline perthite and sodic-calcic amphibole, sharing the petrological and chemical features of A2-type granites. Sri values range from 0.70241 to 0.70424, are similar to those expected for magmas extracted from a Neoproterozoic depleted source and much lower than what would be expected, if there was minor involvement of pre-Neoproterozoic continental crust. The geochemical characteristics indicate that their magma was most plausibly represented by partial melting of juvenile lower crust following the collision between East and West Gondwana at the final stage of the Arabian Shield evolution. The data presented in this study are therefore consistent with an intraplate, post-collisional magmatism formed at the beginning of a transition from convergent to extensional tectonics.

      PubDate: 2013-11-29T00:06:04Z
  • Plio-Pleistocene basanitic and melilititic series of the Bohemian Massif:
           K-Ar ages, major/trace element and Sr–Nd isotopic data
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4
      Author(s): Jaromír Ulrych , Lukáš Ackerman , Kadosa Balogh , Ernst Hegner , Emil Jelínek , Zoltan Pécskay , Antonín Přichystal , Brian G.J. Upton , Jiří Zimák , Radana Foltýnová
      The Plio-Pleistocene volcanic rocks of the Bohemian Massif comprise a compositional spectrum involving two series: an older basanitic series (6.0–0.8Ma) and a younger, melilititic series (1.0–0.26Ma). The former consists of relatively undifferentiated basaltic rocks, slightly silica-undersaturated, with Mg# ranging from 62 to almost primitive mantle-type values of 74. The major and trace element characteristics correspond to those of primitive intra-plate alkaline volcanic rocks from a common sub-lithospheric mantle source (European Asthenospheric Reservoir – EAR) including positive Nb, and negative K and Pb anomalies. 87Sr/86Sr ratios of 0.7032–0.7034 and 143Nd/144Nd of 0.51285–0.51288 indicate a moderately depleted mantle source as for other mafic rocks of the central European volcanic province with signs of HIMU-like characteristics commonly attributed to recycling of subducted oceanic crust in the upper mantle during the Variscan orogeny. The melilititic series is characterized by higher degrees of silica-undersaturation, and high Mg# of 68–72 values, compatible with primitive-mantle-derived compositions. The high OIB-like Ce/Pb (19–47) and Nb/U (32–53) ratios indicate that assimilation of crustal material was negligible. In both series, concentrations of incompatible elements are mildly elevated and 87Sr/86Sr ratios (0.7034–0.7036) and 143Nd/144Nd ratios (0.51285–0.51288) overlap. Variations in incompatible element concentrations and isotopic compositions in the basanitic series and melilititic series can be explained by a lower degree of mantle melting for the latter with preferential melting of enriched mantle domains. The Sr and Nd isotopic compositions of both rock series are similar to those of the EAR. Minor differences in geochemical characteristics between the two series may be attributed to: (i) to different settings with respect to crust and lithospheric mantle conditions in (a) Western Bohemia (WB) and (b) Northeastern Bohemia (NEB) and the Northern Moravia and Silesia (NMS) areas, (ii) a modally metasomatized mantle lithosphere in WB in contrast to cryptically metasomatized domains in the NEB and NMS, (iii) different degrees of partial melting with very low degrees in WB but higher degrees in NEB and NMS. The geochemical and isotopic similarity between the Plio-Pleistocene volcanic rocks and those of the late Cretaceous and Cenozoic (79–6Ma) suggests that their magmas came from compositionally similar mantle sources, that underwent low degrees of melting over an interval of ∼80Ma. The Oligocene to Miocene basanitic series that accompanied the Plio-Pleistoicene basanitic series in the NMS region indicate that they shared a common mantle source. There is no geochemical evidence for thermal erosion of the lithospheric mantle or significant changes in mantle compositions within the time of a weak thermal perturbation in the asthenospheric mantle. These perturbations were caused by a dispersed mantle plume or passively upwelling asthenosphere in zones of lithospheric thinning.

      PubDate: 2013-11-29T00:06:04Z
  • Major, trace element and stable isotope composition of water and muds
           precipitated from the hot springs of Bolivia: Are the waters of the
           spring's potential ore forming fluids?
    • Abstract: Publication date: Available online 23 November 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Giulio Morteani , Peter Möller , Peter Dulski , Christine Preinfalk
      The deposition of metal-rich black or reddish muds by many thermal springs in the Cordilleras and the Altiplano of Bolivia suggest that these geothermal waters may be related to those that once formed the world-class Bolivian tin, silver and gold mineralisation. The discharge temperatures of these springs are as high as 70°C. According to δ18O, δD, tritium data and Ar/N2 ratios these waters are predominantly of meteoric origin. Less than 10% of the discharging thermal water represents deep-seated metal-rich thermal brines of at least 530°C according to carbon exchange between CO2 and CH4. These brines ascend along tectonic faults and mix with low-temperature meteoric water in surface-near aquifers. The meteoric component of the thermal water is recharged in the high Cordilleras with residence times exceeding 50 years. The chemical composition of the thermal water is dominated by the rather inefficient low-temperature leaching of the surface-near aquifer rocks by meteoric water. The small fraction of metal-rich hot deep-seated water is not able to increase the metal content of the water mix to a level sufficient to classify these thermal waters as ore-bearing. Surface-near leaching is supported, e.g., by the B/Li ratios of the spring water of the Western Cordillera and Caleras/Pulacayo in the Eastern Cordillera that correspond very closely to that of the easily leachable glassy inclusions of the outcropping andesitic lavas. The often remarkable metal content of the muds deposited by the springs originate from efficient scavenging of heavy metals by ferric oxyhydroxides. Under the given arid to semi-arid climate the muds are additionally enriched in metals by wind-transported dust. The present study does support a relation of the actual thermal waters with neither the classical subduction-related Upper Tertiary tin, silver and gold mineralisation nor the supposed younger Sb mineralisation of Bolivia.

      PubDate: 2013-11-25T00:07:05Z
  • Genetic classification of magmatic rocks from the Alvand plutonic complex,
           Hamedan, western Iran, based on zircon crystal morphology
    • Abstract: Publication date: Available online 24 November 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Hossein Shahbazi , Sedigheh Salami , Wolfgang Siebel
      The Alvand plutonic complex consists of gabbroic and felsic rocks, the latter can be divided into (1) porphyritic, fine-grained and mylonitic granites and (2) leucocratic granitoids. We investigated the external zircon morphology and their internal structures from all major granitoids of the pluton employing the classic Pupin method supplemented by electron microscope analyses. Zircons of gabbroic rocks are free of visible cores or inclusions and are commonly characterized by {101} pyramids and {100} prisms and show mainly zircon types P5 and D typical for mantel-derived rocks. The zircon population from the porphyritic granite is characterized by the predominance of the pyramidal {211} and prism {110} forms and mainly composed of the subtypes S1, S2, S6 and S7 typical for peraluminous granites of crustal origin. Melt inclusions, recrystallization patches and low-CL intensity rims are typical features in these grains. Zircons from the fine-grained granites are characterized by the predominance of the pyramidal {211} and the prism face {110} and by a preponderance of the subtypes S3, S4, S7 and especially S12 and occasionally S2, L2, L3 and L4, typical for aluminous monzogranites and granodiorites of crustal origin. Some grains have pre-magmatic inherited domains with overgrow rims. The mylonitized granites contain zircons with {101} pyramids and {110} prisms and include subtypes G1, P1, P2, S5 whereas P3, S4, L5 are rarely present, typical for I-type granites. Metamictization, radial cracks and partial overgrowths are prevalent in these zircons. Zircons from the leucocratic granitoids have well-developed magmatic oscillatory zonation and pre-magmatic zircon cores. They are characterized by {101} pyramids and {110} prisms and are mainly composed of subtypes L5, S5, S10 and rarely P1, P2, S2, S3, S4, S7, G1 typical for hybrid calc-alkaline granites.

      PubDate: 2013-11-25T00:07:05Z
  • Preservation of diagenetic products of β-carotene in sedimentary
           rocks from the Lopare Basin (Bosnia and Herzegovina)
    • Abstract: Publication date: Available online 16 November 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Nenad Grba , Aleksandra Šajnović , Ksenija Stojanović , Vladimir Simić , Branimir Jovančićević , Goran Roglić , Vladisav Erić
      Sedimentary rocks from the saline formation of the Lopare Basin were investigated. Sediments contain a moderate amount of immature to marginally mature algal organic matter deposited under slightly reducing to anoxic and slightly saline to hypersaline conditions. Almost all of the samples contain β-carotane in a relatively high quantity, and in some, it represents the most abundant compound in the total distribution of hydrocarbons. The objective of the study was to determine the conditions that are favourable to precursors of β-carotene and/or the preservation of the carotenoid hydrocarbon skeleton. Moreover, the dominant transformation pathways of β-carotene under different redox and salinity conditions, which lead to the formation of aromatic carotenoids were defined. Based on the content of β-carotane, the examined sedimentary rocks are divided into groups A, B and C. Group A does not contain or contains up to 1% of β-carotane, group B contains between 1 and 5% of β-carotane, while group C contains more than 5% of β-carotane in the overall distribution of hydrocarbons. The organic matter (OM) of the sediments of group A is characterized by a higher contribution of prokaryotic precursor organisms, in comparison with the other samples. The OM was deposited in a slightly saline reductive environment, with an increased erosion activity. This environment was unfavourable for the precursors of β-carotene and/or for preservation of its hydrocarbon skeleton. Evidence for the degradation of the poliene chain in β-carotene is the domination of monoaromatic compounds in the aromatic carotenoids distribution. The OM of sediments of groups B and C is similar, predominantly of algal origin deposited in a reducing to anoxic calm carbonate environment with salinity changes from hypersaline to saline. Such reduced to anoxic saline, but not hypersaline environments are most appropriate for precursors of β-carotene and for the preservation of carotenoid skeleton. Cyclization and aromatization of polyene isoprenoid chain, whereby terminal groups remain the main pattern, is the main pathway of β-carotene aromatization in anoxic hypersaline environments, whereas aromatization of terminal 1,1,5-trimethylcyclohexen-5-enyl groups and expulsion of toluene and m-xylene are typical for the reduced to anoxic saline environments.

      PubDate: 2013-11-17T00:06:10Z
  • Holocene climate variation determined from rubidium and strontium contents
           and ratios of sediments collected from the BadainJaran Desert, Inner
           Mongolia, China
    • Abstract: Publication date: Available online 6 November 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Yuanjun Guo , Baosheng Li , Xiaohao Wen , Fengnian Wang , Dongfeng Niu , Yuejun Shia , Yihua Guo , Shuping Jiang , Guanguan Hu
      Rubidium (Rb) and strontium (Sr) contents and ratios were analyzed in 197 sediment samples collected from the CGS1 segment of the Chagelebulu Section in the Badain Jaran Desert of China to study millennial scale climate change during the Holocene. The results showed that the Rb and Sr contents and Rb/Sr ratios were low in the samples of dune sands and loess (Mz<5.64Φ), and those values were high in the samples of loess (Mz>5.64Φ) and paleosols, these data displayed 11 changing cycles in alternation of peaks and valleys in the chart. In addition, the Rb contents were positively correlated with Mz (mean particle diameter) and clay contents. While the correlations were weaker, Sr contents also showed a tendency to increase with increases in the Mz and clay contents. Based on a comprehensive analysis of the distribution of Rb and Sr within the CGS1 segment, it appears that the observed Rb and Sr contents and ratios varied in accordance with fluctuations of the East Asian winter and summer monsoons. In terms of timing and climate, low values (C1–C11) resulting from winter monsoons had a strong correlation with cold events in the North Atlantic: the period C1 corresponded to times ranging from 400a to 1400a and the periods C2, C3, C4, C7, C9, C10, and C11 corresponded to times of 3000a, 4000a, 5900a, 8200a, 9400a, 10,300a, and 11,000a, respectively. The cold event C5 (6200a) was also discovered in the North Atlantic in recent; and C6 (7100a), C8 (8700a) were discovered in some other places of China. These cold events indicated by Rb and Sr contents and ratios in the Chagelebulu Section of the Badain Jaran Desert recorded the regional response of global climate change during the Holocene.

      PubDate: 2013-11-09T00:08:42Z
  • Chemical fluid transport (CFT) A window into Earth and its development
    • Abstract: Publication date: Available online 29 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Werner Schrön
      Gas phase transport according to chemical fluid transport (CFT) in Earth's crust as well as in the solar nebula is characterized by very high transport efficiency. Systematic investigations of mobilization, transport and deposition of gaseous MeX (Me=metal, X=F or Cl) compounds by solid gas equilibrium reactions are suitable to explain numerous extensive accumulations of minerals and ores. More than 40 of the considered chemical elements form volatile MeX compounds. Some elements tend to form MeF compounds, whereas others are more likely to form MeCl compounds. Silicon reacts with HF to form SiF4 and replaces other elements to form MeF compounds at low temperature ranges. Accumulations caused by SiF4 transport explain the formation of numerous quartz varieties and silicate minerals in Earth's crust. Iron most likely reacts with HCl to form FeCl2 as well as FeCl3 and explain the formation of iron or iron compounds. Thermodynamically directed transport from cool to hot areas in connection with cyclic processes increases the transport efficiency of MeX-species. Such species are SiF4, Al2F6, POF3, Cu3Cl3, SnCl4, BF3, GeF4, GeCl4, Ga2Cl6, ZrF4, NbF5 and TiF4. The transport gases SiF4 and POF3 often react with environmental compounds forming pneumatolytic and metasomatical mineral accumulations. CFT is the “motor” of pneumatolytic and metasomatical processes. MeX compounds moving from hot to cool areas are FeCl2, FeCl3, MnCl2, NiCl2, CoCl2, WO2Cl2, MoO2Cl2, GeCl2, GaCl3, SnCl2. Their most spectacular products could be the Fe,Ni iron bodies (taenite/kamacite) known as iron meteorites. They were formed by cyclic processes as well. Thus taenite/kamacite formation by CFT could be an important argument for heterogeneous accretion. For MeX transport processes only halogen compounds HX and temperature gradients are necessary. All examples described here show that mobilization, transport and deposition of MeX compounds follow the same simple principles. In this way CFT can explain global mineral accumulations caused by gas phase transport. Therefore, all products of CFT should be named fluidic rocks (resp. fluidic minerals and ores) in contrast to igneous, sedimentary and metamorphic rocks. The concept “magmatic residual liquid” will be replaced by CFT. The CFT, described here, is possibly operative in interstellar clouds as well, as soon as F, Cl, Fe, Si and other chemical elements are present and the preconditions for CFT are fulfilled.

      PubDate: 2013-11-01T00:06:12Z
  • Geochemical characteristics of stream sediments, sediment fractions,
           soils, and basement rocks from the Mahaweli River and its catchment, Sri
    • Abstract: Publication date: October 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 3
      Author(s): Sansfica M. Young , Amarasooriya Pitawala , Hiroaki Ishiga
      Geochemical variations in stream sediments (n =54) from the Mahaweli River of Sri Lanka have been evaluated from the viewpoints of lithological control, sorting, heavy mineral concentration, influence of climatic zonation (wet, intermediate, and dry zones), weathering, and downstream transport. Compositions of soils (n =22) and basement rocks (n =38) of the catchment and those of <180μm and 180–2000μm fractions of the stream sediments were also examined. The sediments, fractions, soils and basement rocks were analyzed by X-ray fluorescence to determine their As, Pb, Zn, Cu, Ni, Cr, V, Sr, Y, Nb, Zr, Th, Sc, Fe2O3, TiO2, MnO, CaO, P2O5 and total sulfur contents. Abundances of high field strength and ferromagnesian elements in the sediments indicate concentration of durable heavy minerals including zircon, tourmaline, rutile, monazite, garnet, pyriboles, and titanite, especially in <180μm fractions. The sediments show strong correlation between Ti and Fe, further suggesting presence of heavy mineral phases containing both elements, such as ilmenite and magnetite. The basement rocks range from mafic through to felsic compositions, as do the soils. The river sediments lack ultrabasic components, and overall have intermediate to felsic compositions. Elemental spikes in the confluences of tributary rivers and high values in the <180μm fractions indicate sporadic inputs of mafic detritus and/or heavy minerals to the main channel. Al2O3/(K2O+Na2O) and K2O/Na2O ratios of the sediments and LOI values of the soils correlate well with the climatic zones, suggesting intense weathering in the wet zone, lesser weathering in the intermediate zone, and least weathering in the dry zone. Low Sr and CaO contents and Cr/V ratios in stream sediments in the wet zone also suggest climatic influence. Fe-normalized enrichment factors (EFs) for As, Pb, Zn, Cu, Ni and Cr in stream sediments in the main channel are nearly all <1.5, indicating there is no significant environmental contamination. The chemistry of the sediments, rocks and the soils in the Mahaweli River are thus mainly controlled by source lithotype, weathering, sorting, and heavy mineral accumulation.

      PubDate: 2013-10-28T04:32:12Z
  • Petrogenetic links between lepidolite-subtype aplite-pegmatite, aplite
           veins and associated granites at Segura (central Portugal)
    • Abstract: Publication date: October 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 3
      Author(s): Isabel Margarida Horta Ribeiro Antunes , Ana Margarida Ribeiro Neiva , João Manuel Farinha Ramos , Paulo Bravo Silva , Maria Manuela Vinha Guerreiro Silva , Fernando Corfu
      In the Segura area, Variscan S-type granites, aplite veins and lepidolite-subtype granitic aplite-pegmatite veins intruded the Cambrian schist-metagraywacke complex. The granites are syn D3. Aplite veins also intruded the granites. Two-mica granite and muscovite granite have similar ages of 311.0±0.5Ma and 312.9±2.0Ma but are not genetically related, as indicated by their geochemical characteristics and (87Sr/86Sr)311 values. They correspond to distinct pulses of magma derived by partial melting of heterogeneous metapelitic rocks. Major and trace elements suggest fractionation trends for: (a) muscovite granite and aplite veins; (b) two-mica granite and lepidolite-subtype aplite-pegmatite veins, but with a gap in most of these trends. Least square analysis for major elements, and modeling of trace elements, indicate that the aplite veins were derived from the muscovite granite magma by fractional crystallization of quartz, plagioclase, K-feldspar and ilmenite. This is supported by the similar (87Sr/86Sr)311 and δ18O values and the behavior of P2O5 in K-feldspar and albite. The decrease in (87Sr/86Sr)311 and strong increase (1.6‰) in δ18O from two-mica granite to lepidolite-subtype aplite-pegmatite veins, and the behaviors of Ca, Mn and F of hydroxylapatite indicate that these veins are not related to the two-mica granite. The occurrence of amblygonite–montebrasite, lepidolite, cassiterite, columbite-(Fe), columbite-(Mn) and microlite suggests that lepidolite-subtype granitic aplite-pegmatite veins are highly differentiated. Montebrasite shows a heterogeneous Na distribution and secondary lacroixite was identified in some montebrasite areas enriched in Na. Unusual Mn>Fe cassiterite is zoned, with the alternating darker zones being strongly pleochroic, oscillatory zoned, and containing more Nb and Ta than the lighter zones. Inclusions of muscovite, apatite, tapiolite-(Fe), ixiolite and microlite are present both in lighter and darker zones of cassiterite. It shows exsolutions of columbite-(Fe), columbite-(Mn,Fe) and columbite-(Mn), particularly in darker zones.

      PubDate: 2013-10-28T04:32:12Z
  • Editorial Board
    • Abstract: Publication date: October 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 3

      PubDate: 2013-10-28T04:32:12Z
  • Major and trace element geochemistry of Lake Bogoria and Lake Nakuru,
           Kenya, during extreme draught
    • Abstract: Publication date: October 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 3
      Author(s): Franz Jirsa , Martin Gruber , Anja Stojanovic , Steve Odour Omondi , Dieter Mader , Wilfried Körner , Michael Schagerl
      The physico-chemical properties of water samples from the two athalassic endorheic lakes Bogoria and Nakuru in Kenya were analysed. Surface water samples were taken between July 2008 and October 2009 in weekly intervals from each lake. The following parameters were determined: pH, salinity, electric conductivity, dissolved organic carbon (DOC), the major cations (FAAS and ICP-OES) and the major anions (IC), as well as certain trace elements (ICP-OES). Samples of superficial sediments were taken in October 2009 and examined using Instrumental Neutron Activation Analysis (INAA) for their major and trace element content including rare earth elements (REE). Both lakes are highly alkaline with a dominance of Na>K>Si>Ca in cations and HCO3 >CO3 >Cl>F>SO4 in anions. Both lakes also exhibited high concentrations of Mo, As and fluoride. Due to an extreme draught from March to October 2009, the water level of Lake Nakuru dropped significantly. This created drastic evapoconcentration, with the total salinity rising from about 20‰ up to 63‰. Most parameters (DOC, Na, K, Ca, F, Mo and As) increased with falling water levels. A clear change in the quality of DOC was observed, followed by an almost complete depletion of dissolved Fe from the water phase. In Lake Bogoria the evapoconcentration effects were less pronounced (total salinity changed from about 40‰ to 48‰). The distributions of REE in the superficial sediments of Lake Nakuru and Lake Bogoria are presented here for the first time. The results show a high abundance of the REE and a very distinct Eu depletion of Eu/Eu*=0.33–0.45.

      PubDate: 2013-10-28T04:32:12Z
  • Geology and geochemistry of Iberian roofing slates
    • Abstract: Publication date: October 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 3
      Author(s): Victor Cárdenes , Alvaro Rubio-Ordoñez , Carmela Monterroso , Lope Calleja
      This article analyzes the geochemical and mineralogical composition of the roofing slate deposits of the Iberian Peninsula. Most roofing slate deposits are found on Middle and Upper Ordovician terrains, although there are also deposits in the Ediacaran, Cambrian and Devonian terrains. Samples of slate were taken in most of the active quarries of the Iberian Peninsula, and being analyzed by X-ray Diffraction and Fluorescence. Each lithotect or slate productive formation has its own specific proportions of major and trace elements, being able to differentiate between them by using these relationships. This fact is particularly interesting in geological exploration and prospecting, as it allows knowing exactly the slate lithotect, and also for restoration work in the architectural heritage, due to the ability of identifying the source of the original slate tiles.

      PubDate: 2013-10-28T04:32:12Z
  • Origin of dolomite in the Late Jurassic platform carbonates, Bolkar
           Mountains, Central Taurides, Turkey: Petrographic and geochemical evidence
    • Abstract: Publication date: October 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 3
      Author(s): M. Ziya Kırmacı
      The Late Jurassic-early Senonian Cehennemdere Formation extending in an E-W direction in a wide area at the south of the Bolkar Mountains (Central Taurides, Turkey) is composed of platform carbonates. The formation was deposited in an environment that was being transformed from a shallow carbonate platform to an open shelf and a continental slope, and was buried until late Paleocene uplift. The formation, with a thickness of about 360m, was chiefly developed as textures consisting of mudstone and wackestone and has been commonly dolomitized. Based on petrographic and geochemical properties, four types of replacement dolomites and two types of dolomite cements were distinguished. Replacement dolomite (RD), which is cut by low-amplitude stylolites developed as (1) fine crystalline planar-s dolomite (RD1); (2) medium crystalline planar-s dolomite (RD2); (3) medium-coarse crystalline planar-e dolomite (RD3) and; (4) coarse crystalline planar-s (e) dolomite (RD4). Two types of dolomite cements (CD) observed in low abundance and overlie low-amplitude stylolites: (1) coarse crystalline dolomite cement (CD1) filling dissolution voids and fractures in RD1 dolomites, and; (2) rim dolomite cement (CD2) that commonly develops on the space-facing surfaces of RD4 dolomite. Replacement dolomites are non-stoichiometric (Ca54–59Mg41–46), have similar geochemical properties, and are generally dull red/non luminescent in appearance. Replacement dolomite is represented by δ18O values from −4.5 to −0.5‰ VPDB, δ13C values of −0.7 to 2.7‰ VPDB, and 87Sr/86Sr ratios ranging from 0.707178 to 0.707692. Petrographic and geochemical data indicate that replacement dolomite (particularly RD2, RD3, and RD4 dolomite) was formed at shallow-intermediate burial depths during the Late Jurassic-Early Cretaceous, from seawater and/or from slightly modified seawater. The replacement dolomite (RD) was then recrystallized at increased burial depths and temperatures. Dolomite cements are similar to replacement dolomites in that they are non-stoichiometric (Ca55Mg45) and have similar trace element compositions. CD1 dolomite, which cuts low-amplitude stylolites, was formed during intermediate to deep burial following stylolite development. CD2 dolomite was precipitated in intercrystal pores in association with RD4 dolomite. Remaining pore space was filled with bitumen.

      PubDate: 2013-10-28T04:32:12Z
  • Clinopyroxene chemistry in Tertiary alkaline volcanic rocks from Taleghan,
           central Alborz, Iran: Implications for two parental melts
    • Abstract: Publication date: Available online 21 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Mohammad Reza Ghorbani , Ahmad Reza Ahmadi , Massimo Tiepolo , Antonio Langone
      In the Taleghan area of Alborz mountain range, two distinct units of alkaline rocks are identified. Whole rock major and trace element data does not provide a clue as to their common or different parental melts. However, major and trace element geochemistry of their included clinopyroxene phenocrysts, combined with the whole rock data, helped to infer that two parental magmas were involved in the evolution of volcanic succession in the Taleghan area.

      PubDate: 2013-10-23T23:06:12Z
  • The Bizielle vein (valle de Gistain): a case of iron oxide transformations
           at the Pyrenees of Spain
    • Abstract: Publication date: Available online 15 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): I. DeFelipe , I. Fanlo , E. Mateo , I. Subías
      The Bizielle vein has some unique features among the Pyrenean alpine veins that allow us to address the question of the nature of iron oxides transformations under low temperature hydrothermal conditions, which is well known to prevailed over wide areas of western Europe between early Triassic to early Cretaceous times. Isotopic studies indicate a deep-seated origin of the ore-forming fluids and suggest that the metals were leached from the Variscan basement (mainly from granites). Isotopic geothermometry and regional evidences point to a 250°C and reducing fluid, being SH2 the predominant S specie. Under such conditions, the proposed in situ deposition of hematite is a consequence of Fe carbonates dissolution and oxidation involving dissolution/precipitation processes in the sense of Putnis. Non-redox model is a quite plausible origin for subsequent hematite to magnetite conversion.

      PubDate: 2013-10-16T00:30:20Z
  • Groundwater geochemistry of Ain Azel area, Algeria
    • Abstract: Publication date: Available online 8 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Lazhar Belkhiri , Lotfi Mouni
      Hydrogeochemical data for 18 groundwater samples and 11 hydrochemical parameters were subjected to Q- and R- mode cluster analysis and inverse geochemical modeling. Q-mode cluster analysis resulted in three distinct water types (brackish water type, saline water type and highly saline water type). R-mode cluster analysis led to the conclusion that there water-rock interaction is the major source of contamination for the groundwater in the area. Geochemical modeling results show that carbonates, gypsum, halite, carbon dioxide (gas), and chlorite are dissolving, whereas Ca-montmorillonite, gibbsite, illite, K-mica, kaolinite, and quartz are mostly precipitating along different flow paths in the groundwater system of the area

      PubDate: 2013-10-11T23:06:12Z
  • Geochemical features and origin of natural gas in heavy oil area of the
           Western Slope, Songliao Basin, China
    • Abstract: Publication date: Available online 4 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Guangyou Zhu , Shuichang Zhang , Barry Jay Katz , Jin Su , Xue Wang , Zihui Feng , Jie Cui , Xingwang Liu
      The Western Slope of the Songliao Basin is rich in heavy oil resources (> 70×108 bbl), around which there are shallow gas reservoirs (∼ 1.0×1012 m3). The gas is dominated by methane with a dryness over 0.99, and the non-hydrocarbon component being overwelmingly nitrogen. Carbon isotope composition of methane and its homologs is depleted in 13C, with δ13C1 values being in the range of -55‰ to -75‰, δ13C2 being in the range of -40‰ to -53‰ and δ13C3 being in the range of -30‰ to -42‰, respectively. These values differ significantly from those solution gases source in the Daqing oilfield. This study concludes that heavy oils along the Western Slope were derived from mature source rocks in the Qijia-Gulong Depression, that were biodegraded. The low reservoir temperature (30-50°C) and low salinity of formation water with neutral to alkaline pH (NaHCO3) appeared ideal for microbial activity and thus biodegradation. Natural gas along the Western Slope appears mainly to have originated from biodegradation and the formation of heavy oil. This origin is suggested by the heavy δ13C of CO2 (-18.78 ∼ 0.95 ‰) which suggests that the methane was produced via fermentation as the terminal decomposition stage of the oil

      PubDate: 2013-10-07T23:06:35Z
  • The Bulk Composition of Mars
    • Abstract: Publication date: Available online 5 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): G. Jeffrey Taylor
      An accurate assessment of the bulk chemical composition of Mars is fundamental to understanding planetary accretion, differentiation, mantle evolution, the nature of the igneous parent rocks that were altered to produce sediments on Mars, and the initial concentrations of volatiles such as H, Cl and S, important constituents of the Martian surface. This paper reviews the three main approaches that have been used to estimate the bulk chemical composition of Mars: geochemical/cosmochemical, isotopic, and geophysical. The standard model is one developed by H. Wänke and G. Dreibus in a series of papers, which is based on compositions of Martian meteorites. Since their groundbreaking work, substantial amounts of data have become available to allow a reassessment of the composition of Mars from elemental data, including tests of the basic assumptions in the geochemical models. The results adjust some of the concentrations in the Wänke-Dreibus model, but in general confirm its accuracy. Bulk silicate Mars has roughly uniform depletion of moderately volatile elements such as K (0.6 x CI), and strong depletion of highly volatile elements (e.g., Tl). The highly volatile elements are within uncertainties uniformly depleted at about 0.06 CI abundances. The highly volatile chalcophile elements are likewise roughly uniformly depleted, but with more scatter, with normalized abundances of 0.03 CI. Bulk planetary H2O is much higher than estimated previously: it appears to be slightly less than in Earth, but D/H is similar in Earth and Mars, indicating a common source of water-bearing material in the inner solar system. K/Th ranges from ∼3000 to ∼5000 among the terrestrial planets, a small range compared to CI chondrites (19,000). FeO varies throughout the inner solar system: ∼3 wt% in Mercury, 8wt % in Earth and Venus, and 18wt % in Mars. These differences can be produced by varying oxidation conditions, hence do not suggest the terrestrial planets were formed from fundamentally different materials. The broad chemical similarities among the terrestrial planets indicate substantial mixing throughout the inner solar system during planet formation, as suggested by dynamical models

      PubDate: 2013-10-07T23:06:35Z
  • The role of heterogenetic mantle in the genesis of adakites northeast of
           Sanandaj, northwestern Iran
    • Abstract: Publication date: Available online 7 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Hossein Azizi , Yoshihiro Asahara , Motohiro Tsuboi , Kento Takemura , Saman Razyani
      In the northern part of the Sanandaj-Sirjan Zone (SSZ), northwestern Iran, there are a number of young (10–11 Ma) dismembered volcanic complexes that extend parallel to the Zagros Suture Zone in a northwest–southeast direction. The major lithologies associated with these complexes include trachyte, andesite, dacite and rhyolite. These rocks are characterized by high SiO2 (>60wt.%) and Al2O3 (>15wt.%), low MgO (<2wt.%) and high Sr/Y (>30) and La/Yb (>25) ratios. Initial 87Sr/86Sr ratios based on an age of 11 Ma (Ar-Ar dating) are relatively high (0.7070 to 0.7079), and ɛt Nd values are relatively low (between -4 and -3). Values of ƒSm are negative and fluctuate between -0.5 and zero; values of ƒRb vary between +3.5 and +8. Analyses of chemical compositions confirm that these rocks belong to the adakite group. The Sr-Nd isotope ratios indicate that these rocks are distinct from adakites derived from partial melting of oceanic slabs or lower continental crust and suggest that the parent magma originated from the metasomatic mantle wedge above the oceanic slab in an active continental margin. Furthermore, the eruption of high-Nb basalts (HNBs) in this area supports the role of metasomatic mantle in the genesis of these adakites. Adakites in the northern SSZ are likely produced by 1) crystallization at high pressure of minerals such as garnet or amphibole from normal basaltic magma (e.g., high-Mg basalt) above the subduction zone, or 2) melting of metasomatic mantle at high pressure in the garnet stability field.

      PubDate: 2013-10-07T23:06:35Z
  • Geochemical features of the Matomb alluvial rutile from the Neoproterozoic
           Pan-African belt, Southern Cameroon
    • Abstract: Publication date: Available online 26 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Jean Camille Tonje , Paul-Désiré Ndjigui , Brunot Nyeck , Paul Bilong
      The Matomb region constitutes an important deposit of detrital rutile. The rutile grains are essentially coarse (> 3mm), tabular and elongated, due to the short sorting of highly weathered detritus. This study reports the major, trace, and rare-earth element distribution in the bulk and rutile concentrated fractions. The bulk sediments contain minor TiO2 concentrations (1 - 2wt.%), high SiO2 contents (∼77 - 95wt.%) and variable contents in Al2O3, Fe2O3, Zr, Y, Ba, Nb, Cr, V, and Zn. The total REE content is low to moderate (86-372ppm) marked by high LREE-enrichment (LREE/HREE ∼ 5 to 25.72) and negative Eu anomalies (Eu/Eu* ∼ 0.51 - 0.69). The chemical index of alteration (CIA) shows that the source rocks are highly weathered, characteristic of humid tropical zone with the development of ferrallitic soils. In the concentrated fractions, TiO2 abundances exceed 94wt.%. Trace elements with high contents include V, Nb, Cr, Sn, and W. These data associated with several binary diagrams show that rutile is the main carrier of Ti, V, Nb, Cr, Sn, and W in the alluvia. The REE content is very low (1 to 9ppm) in spite of the LREE-abundance (LREE/HREE ∼ 4 to 40). The rutile concentrated fractions exhibit anomalies in Ce (Ce/Ce* ∼ 0.58 to 0.83; ∼ 1.41 - 2.50) and Eu (Eu/Eu* ∼ 0.42; 1.20 - 1.64). The high (La/Sm)N, (La/Yb)N and (Gd/Yb)N ratios indicate high REE fractionation

      PubDate: 2013-09-29T23:06:54Z
  • Application of spectrum–area fractal model to identify of
           geochemical anomalies based on soil data in Kahang porphyry-type Cu
           deposit, Iran
    • Abstract: Publication date: Available online 21 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Peyman Afzal , Hamid Harati , Younes Fadakar Alghalandis , Amir Bijan Yasrebi
      The aim of this study is to identify geochemical anomalies using power spectrum–area (S–A) method based on the grade values of Cu, Mo and Au in 2709 soil samples collected from Kahang porphyry-type Cu deposit, Central Iran. S–A log–log plots indicated that there are three stages of Cu, Mo and Au enrichment. The third enrichment was considered as the main stage for the presence of Cu, Mo and Au at the concentrations above 416ppm, 23ppm and 71ppb, respectively. Elemental anomalies are positively associated with monzo–granite–diorite and breccias units which are in the central and western parts of the deposit. The anomalies are located within the potassic, phyllic and argillic alteration types and also there is the positive correlation between the anomalies and nearing faults in the studied area. The results obtained via fractal model were interpreted accordingly to incorporate the information for the mineralized areas including detailed geological map, structural analysis and alterations. The results show that S–A multifractal modeling is applicable for anomalies delineation based on soil data.

      PubDate: 2013-09-26T03:37:00Z
  • The impact environment of the Hadean Earth
    • Abstract: Publication date: Available online 24 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Oleg Abramov , David A. Kring , Stephen J. Mojzsis
      Impact bombardment in the first billion years of solar system history determined in large part the initial physical and chemical states of the inner planets and their potential to host biospheres. The range of physical states and thermal consequences of the impact epoch, however, are not well quantified. Here, we assess these effects on the young Earth's crust as well as the likelihood that a record of such effects could be preserved in the oldest terrestrial minerals and rocks. We place special emphasis on modeling the thermal effects of the late heavy bombardment (LHB) – a putative spike in the number of impacts at about 3.9Gyr ago – using several different numerical modeling and analytical techniques. A comprehensive array of impact-produced heat sources was evaluated which includes shock heating, impact melt generation, uplift, and ejecta heating. Results indicate that ∼1.5–2.5vol.% of the upper 20km of Earth's crust was melted in the LHB, with only ∼0.3–1.5vol.% in a molten state at any given time. The model predicts that approximately 5–10% of the planet's surface area was covered by >1km deep impact melt sheets. A global average of ∼600–800m of ejecta and ∼800–1000m of condensed rock vapor is predicted to have been deposited in the LHB, with most of the condensed rock vapor produced by the largest (>100-km) projectiles. To explore for a record of such catastrophic events, we created two- and three-dimensional models of post-impact cooling of ejecta and craters, coupled to diffusion models of radiogenic Pb*-loss in zircons. We used this to estimate what the cumulative effects of putative LHB-induced age resetting would be of Hadean zircons on a global scale. Zircons entrained in ejecta are projected to have the following average global distribution after the end of the LHB: ∼59% with no impact-induced Pb*-loss, ∼26% with partial Pb*-loss and ∼15% with complete Pb*-loss or destruction of the grain. In addition to the relatively high erodibility of ejecta, our results show that if discordant ca. 3.9Gyr old zones in the Jack Hills zircons are a signature of the LHB, they were most likely sourced from impact ejecta.

      PubDate: 2013-09-26T03:37:00Z
  • Formation of solid bituminous matter in pegmatites: constraints from
           experimentally formed organic matter on microporous silicate minerals
    • Abstract: Publication date: Available online 25 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Roman Golowin , Astrid Holzheid , Frank D. Sönnichsen , Nikita V. Chukanov
      The formation of solid bituminous matter (SBM) on surfaces of microporous silicates was experimentally studied at pressure and temperature conditions typical of late-stage magmatic and hydrothermal processes. Aliquots of microporous silicate minerals (zorite and kuzmenkoite-Mn, Lovozero Alkaline Massif, Kola Peninsula, Russia) were exposed to solid or liquid organic carbon sources (natural brown coal and liquid 1-hexene for synthesis purposes) in a 0.1M NaCl-solution for 7 days, at constant pressure (50MPa), and at three individual temperatures (200, 275, and 300°C). No thermal decomposition of the solid organic sources happened at 200°C and only a thin film of brown coal derivatives on the silicates’ surfaces and no formation of SBM were observed at 275°C and 300°C. But solid bituminous matter on the surfaces of both microporous silicates were detected in experiments with liquid 1-hexene as organic carbon source and at temperatures of 275°C and 300°C with a more pronounced formation of SBM at 300°C compared to 275°C. The aromatic and aliphatic hydrocarbons, as well as alcoholic compounds of the experimentally produced SBM are similar, if not even partly identical, with natural SBM occurrences of the Khibiny and Lovozero Massifs, Kola Peninsula, Russia, and from the Viitaniemi granitic pegmatite, Finland, as shown by FT-IR and 1H-NMR spectroscopy. This strengthens the hypothesis of formation of natural solid bituminous matter by catalytic reactions between microporous Ti-, Nb- and Zr-silicates and hydrocarbons at postmagmatic hydrothermal conditions

      PubDate: 2013-09-26T03:37:00Z
  • Geochemical and Sr–Nd isotopic characteristics of Murgul (Artvin)
           volcanic rocks in the Eastern Black Sea Region (Northeast Turkey)
    • Abstract: Publication date: Available online 11 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Ferkan Sipahi , M. Burhan Sadıklar , Cüneyt Şen
      The studied volcanic rocks are footwall and hanging wall dacites from the Murgul mine and the surrounding area. Moreover, the hanging wall dacites contain enclaves. Footwall dacite contains biotite, whereas hanging wall dacitic rocks contain hornblende as a ferromagnesian mineral. The enclaves in the hanging wall dacite have sizes that range from 1cm to 20cm and contain hornblende as a ferromagnesian mineral. The volcanic rocks show tholeiitic and transitional affinities. They are rich in large ion lithophile element and light rare earth element with pronounced depletion of high field strength elements. The chondrite-normalized rare earth element patterns (LaN/LuN =1.47–5.12) show low to medium enrichment, which reveal that the rocks were obtained from similar sources in Murgul volcanic rocks. The initial 87Sr/86Sr values range from 0.70442 to 0.70525, and the initial 143Nd/144Nd values range from 0.512741 to 0.512770. The main solidification processes involved in the evolution of the volcanic rocks consist of fractional crystallization with minor amounts of crustal contamination and magma mixing. All geochemical data support that these rocks originated from andesitic magma, and that the parental magma of the rocks were probably derived from an enriched upper mantle, previously modified by subduction-induced metasomatism in a geodynamic setting.

      PubDate: 2013-09-11T23:05:28Z
  • Geochemistry and behavior of REE in stream sediments close to an old Sn-W
           mine, Ribeira, Northeast Portugal
    • Abstract: Publication date: Available online 6 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): M. Manuela Vinha G. Silva , Sérgio P. Lopes , Elsa C. Gomes
      The abandoned Sn-W Ribeira mine, northeast of Portugal, contained quartz veins with cassiterite, wolframite, scheelite, pyrite, arsenopyrite, sphalerite, chalcopyrite, manganocolumbite, bismuthinite, native bismuth, phosphates and carbonates. The exploration took place on the northern slope of the Viveiros stream, which is an affluent of the Sabor River. The waste-rock dumps and tailings were deposited on the hillside, close to the mine and are nowadays exposed to significant weathering and erosion, as they are not vegetated. The eroded material is transported by the Viveiros stream toward the Sabor River. A seasonal stream drains the tailings. The stream sediments samples were collected along the Viveiros stream, in the seasonal stream, in a seasonal spring at the bottom of the tailings, in the Sabor River and in other streams not affected by mine workings, following the mine influence along the Viveiros stream and in the Sabor River (1.2km away from the mine workings). The data show that the degree of pollution increases along the Viveiros stream, especially in winter. The highest degree of pollution is for As, In, W, Sn and Bi. The sediments from the drainage of the main tailings are particularly polluted during winter, by Bi, In and Sn. The sedimentary precipitate from the spring is polluted in Cu, As, In, Sn, Ta, W, Bi, Zn, Nb, Ag, Sb and Ta. The sediments from the Sabor River are significantly polluted by As, Ag, In, Sn, W and Bi. The sediments from the regional streams, Viveiros stream and Sabor River have similar REE (NASC normalized) patterns (ΣREE=131.7–185.9mg/kg, LaN/LuN =1.23–1.42 and Eu/Eu*=1.02), while those from the seasonal stream, crossing the main tailings, are enriched in REE (ΣREE=250.3–283.6mg/kg, LaN/LuN =1.6–2.09 and Eu/Eu*=0.96). The general decrease in LaN/LuN values with increase in total Fe2O3 can be explained by the partitioning of HREE to the solid Fe-oxides phase. The sedimentary precipitate and coatings, which are mainly formed by Fe-oxy-hydroxides, but also contain jarosite, are impoverished in all REE. The impoverishment can be explained by the release of REE from the surface of the Fe-oxy-hydroxides, which occurs due to a local lowering of pH, caused by jarosite dissolution. During successive alternate cycles of wet and dry conditions, takes place the formation of Fe-oxy-hydroxides and jarosite in the sedimentary precipitate and coatings. The subsequent dissolution of jarosite releases acidity, thus promoting de-sorption of REE from the Fe-oxy-hydroxides mineral phases.

      PubDate: 2013-09-07T23:05:21Z
  • Geochemical comparison of waters and stream sediments close to abandoned
           Sb-Au and As-Au mining areas, northern Portugal
    • Abstract: Publication date: Available online 5 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Paula C.S. Carvalho , Ana M.R. Neiva , Maria M.V.G. Silva , Eduardo A. Ferreira da Silva
      Waters from abandoned Sb-Au mining areas have higher Sb (up to 2138μgL−1), As (up to 1252μgL−1) and lower Al, Zn, Li, Ni and Co concentrations than those of waters from the As-Au mining area of Banjas, which only contain up to 64μgL−1 As. In general, Sb occurs mainly as SbO3 − and As H2AsO4 −. In general, waters from old Sb-Au mining areas are contaminated in Sb, As, Al, Fe, Cd, Mn, Ni and NO2 −, whereas those from the abandoned As-Au mining area are contaminated in Al, Fe, Mn, Ni, Cd and rarely in NO2 −. Waters from the latter area, immediately downstream of mine dumps are also contaminated in As. In stream sediments from Sb-Au and As-Au mining areas, Sb (up to 5488mgkg−1) and As (up to 235mgkg−1) show a similar behaviour and are mainly associated with the residual fraction. In most stream sediments, the As and Sb are not associated with the oxidizable fraction, while Fe is associated with organic matter, indicating that sulphides (mainly arsenopyrite and pyrite) and sulphosalts containing those metalloids and metal are weathered. Arsenic and Sb are mainly associated with clay minerals (chlorite and mica; vermiculite in stream sediments from old Sb-Au mining areas) and probably also with insoluble Sb phases of stream sediments. In the most contaminated stream sediments, metalloids are also associated with Fe phases (hematite and goethite, and also lepidocrocite in stream sediments from Banjas). Moreover, the most contaminated stream sediments correspond to the most contaminated waters, reflecting the limited capacity of stream sediments to retain metals and metalloids.

      PubDate: 2013-09-07T23:05:21Z
  • Fossil fuel compounds from fly dust in recent organic matter of southern
           Poland peats
    • Abstract: Publication date: Available online 3 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Monika J. Fabiańska , Artur Szymczyk , Magdalena Chłapik
      Several samples of peat from 6 bogs located in southern Poland were investigated for occurrence and distribution types of biomarkers present in their extractable organic matter fraction. It was found that there are inputs from two different sources of organic compounds differing in their characteristics and origin: (1) recent immature peat organic matter deposited in situ which is the source of all polar functionalized compounds, most of n-alkanes, and acyclic isoprenoids, and (2) mature fossil fuels, most probably bituminous coals from the Upper Silesia Coal Basin of vitrinite reflectance equivalent values of 0.9–1.1%. The latter compounds were most probably transported with fly ash to bogs from nearby settlements utilizing such fuel in domestic ovens. This group includes pentacyclic triterpenoids (hopanes and moretanes), minor amounts of n-alkanes, and numerous alkyl naphthalenes and alkyl phenanthrenes. All these compounds show distributions and values of geochemical ratios characteristic for mature organic matter confirming there ex situ origin.

      PubDate: 2013-09-03T23:05:53Z
  • An SVM-based machine learning method for the separation of alteration
           zones in Sungun porphyry copper deposit
    • Abstract: Publication date: Available online 2 September 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Maliheh Abbaszadeh , Ardeshir Hezarkhani , Saeed Soltani-Mohammadi
      Sungun porphyry copper deposit is in East Azarbaijan province, NW of Iran. There exist four hypogene alteration types in Sungun: potassic, propylitic, potassic–phyllic, and phyllic. Copper mineralization is essentially associated more with the potassic and less with the phyllic alterations and their separation is, therefore, quite important. This research has tried to separate these two alteration zones in Sungun porphyry copper deposit using the Support Vector Machine (SVM) method based on the fluid inclusion data, and seven variables including homogenization temperatures, salinity, pressure, depth, density and the Cu grade have been measured and calculated for each separate sample. To apply this method, use is made of the radial basis function (RBF) as the kernel function. The best values for λ and C (the most important SVM parameters) that perform well in the training and test data are 0.0001 and 1, respectively. If these values for λ and C are applied, the phyllic and potassic alteration zones in the training and test data will be separated with an accuracy of about 95% and 100%, respectively. This method can help geochemists in separating the alteration zones because classifying and separating samples microscopically is not only very hard, but also quite time and money consuming.

      PubDate: 2013-09-03T23:05:53Z
  • Use of biomarkers indices in a sediment core to evaluate potential
           pollution sources in a subtropical reservoir in Brazil
    • Abstract: Publication date: Available online 24 August 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Juan Sánez , Sandro Froehner , Filipe Falcão
      The presence of PAHs, n-alkanes, pristane, and phytanes in core sediment from the Vossoroca reservoir (Parana, southern Brazil) was investigated. The total concentration of the 16 PAHs varied from 15.5 to 1646μgkg−1. Naphthalene was present in all layers (3.34–74.0μgkg−1). The most abundant and dominant n-alkanes were n-C15 and n-C36, with average concentrations of 198.1±46.8 and 522.9±167.7μgkg−1, respectively. Lighter n-alkanes were distributed more evenly through the layers and showed less variation, specially n-C9, n-C12, and n-C18, with average concentrations of 14.6±3.0, 31.6±1.9, and 95.0±5.2μgkg−1, respectively; heavier n-alkanes were more unevenly distributed. The study of the biomarker ratios indicates a slight influence from the nearby Highway BR 376: deposit of sediments coming from the pavement and sources of pyrolytic origin from the heavy traffic of vehicles and a gas station close to the sample point. In addition to this, the n-alkanes ratio analysis indicates that the region receives significant contribution from higher plants, with low contribution from autochthonous organic matter origin. Identified PAHs suggest pyrogenic sources formed during the pyrolysis of fossil fuels and direct influence from the heavy traffic from the nearby highway. The DBahA was found to be related to the contribution of particulate pavement, but only in significant concentrations after 15cm depth. Sediment fractions seem to be oxic, and the absence of phytane can be explained by several periods of bioturbation and tidal. In general, when compared with other studied sediments, the area seems low-polluted.

      PubDate: 2013-08-26T23:10:54Z
  • Geochronology and geochemistry of Middle Devonian mafic dykes in the East
           Kunlun orogenic belt, Northern Tibet Plateau: Implications for the
           transition from Prototethys to Paleotethys orogeny
    • Abstract: Publication date: Available online 24 August 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Fuhao Xiong , Changqian Ma , Hong’an Jiang , Bin Liu , Jian Huang
      The tectonic transition from Prototethys to Paleotethys orogeny in the East Kunlun orogenic belt is not completely clear, and is a major unresolved geologic issue in Northern Tibet Plateau. Here, we present zircon geochronology, whole-rock elemental and zircon Hf isotopic geochemistry for newly discovered mafic dykes in the East Kunlun orogenic belt, to provide constraints on this issue. The studied mafic dykes are hornblende gabbros, consisting of hornblende (60–65vol.%), plagioclase (15–25vol.%) and augite and biotite (0–5vol.%). LA–ICP–MS zircon U–Pb dating shows that these mafic dykes were emplaced at about 393Ma. All the mafic dykes are characterized by high contents of CaO (8.82–11.48wt.%), MgO (9.07–11.39wt.%), V (275–336ppm), Cr (370–467ppm) and Ni (78.3–120ppm), with high Mg# (63–67), flat CI-normalized REE distribution and depleted ɛHf(t) values (2.03–5.35), showing tholeiitic affinities and geochemical characteristics similar to those of mid-ocean ridge basalts. They were derived from low degree (about 5–15%) partial melting of a fertile spinel lherzolite source, which have been metasomatized by fluids introduced to the mantle by former subducted slab. The geologic–petrologic evidence suggests that the mafic dykes were emplaced in a shift tectonic setting related to continental rifting, which was caused by the extensional collapse related to the lithospheric thinning after the Prototethys orogeny. The delamination-induced thermal disturbance and extensional decompression triggered partial melting of the mantle and the emplacement of the mafic dykes. Combined with previous work, we propose that the Middle Devonian mafic dykes may be the early magmatic response to the transition from Prototethys to Paleotethys marking the opening of the Paleotethys in the East Kunlun orogenic belt.

      PubDate: 2013-08-26T23:10:54Z
  • Geochemistry of an ENE–WSW to NE–SW trending ∼2.37Ga
           mafic dyke swarm of the eastern Dharwar craton, India: Does it represent a
           single magmatic event?
    • Abstract: Publication date: Available online 24 August 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Rajesh K. Srivastava , M. Jayananda , Gulab C. Gautam , V. Gireesh , Amiya K. Samal
      A vast tract of ENE–WSW to NE–SW trending mafic dyke swarm transects Archaean basement rocks within the eastern Dharwar craton. Petrographic data reveal their dolerite/olivine dolerite or gabbro/olivine gabbro composition. Geochemical characteristics, particularly HFSEs, indicate that not all these dykes are co-genetic but are probably derived from more than one magma batch and different crystallization trends. In most samples the LaN/LuN ratio is at ∼2, whereas others have a LaN/LuN ratio >2 and show higher concentrations of high-field strength elements (HFSEs) than the former group. As a consequence, we assume that the ENE–WSW to NE–SE trending mafic dykes of the eastern Dharwar craton do not represent one single magmatic event but were emplaced in two different episodes; one of them dated at about 2.37Ga and another probably at about 1.89Ga. Trace element modelling also supports this inferen older mafic dykes are derived from a melt generated through ∼25% melting of a depleted mantle, whereas the younger set of dykes shows its derivation through a lower degree of melting (∼15%) of a comparatively enriched mantle source.

      PubDate: 2013-08-26T23:10:54Z
  • Mercury distribution amongst co-existing silicates within the Bushveld
    • Abstract: Publication date: Available online 21 August 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Pelele B. Lehloenya , Frederick Roelofse
      Thirty separates of plagioclase, orthopyroxene and clinopyroxene from the lower Main Zone of the Northern Limb of the Bushveld Complex were analysed for their mercury contents using combustion atomic absorption spectroscopy with gold amalgamation pre-concentration. The average mercury contents of plagioclase, orthopyroxene and clinopyroxene were found to be 0.9ppb, 1.2ppb and 1.1ppb, respectively. Mercury within the separates does not vary systematically with any of the major element oxides present in the minerals. Based on a positive 1:1 correlation between mercury in orthopyroxene and clinopyroxene, we estimate DOpx Hg ≈DCpx Hg, and on this basis, can exclude the presence of significant Hg2+ within the melts from which these minerals crystallised. The lack of correlation between mercury in plagioclase and that in the mafic silicates may suggest diffusional loss of the element from the former during slow cooling under magmatic conditions and better retention of mercury by the mafic silicates under the same conditions. Alternatively and more likely, this lack of correlation may support earlier arguments based on distinct Sr-isotopic disequilibrium between co-existing plagioclase and mafic silicates, that plagioclase and the mafic silicates in the Northern Limb of the Bushveld Complex may have crystallised from different melts within a variably contaminated, sub-Bushveld staging chamber.

      PubDate: 2013-08-23T08:07:59Z
  • Hydrochemical characteristics and controlling factors for waters’
           chemical composition in the Tarim Basin, Western China
    • Abstract: Publication date: Available online 31 July 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Ying Bo , Chenglin Liu , Pengcheng Jiao , Yongzhi Chen , Yangtong Cao
      This paper covers the chemical and isotopic composition of river water, groundwater from wells (15–25m), saline spring water and stagnant surface water providing evidence for controlling factors of water composition and water evolution process in the Tarim Basin, Xinjiang, western China. Analytical data for major and minor ions of totaling 537 water samples were obtained from both years of teamwork and old reference materials. It is found that the ion background value ratio SO4/Cl for river water (2.75) of the Tarim Basin is two times higher than that of the Qaidam Basin (0.88) and 18 times higher than seawater (0.14); K/Cl of these two basins (0.06 and 0.07) are all two times higher than seawater (0.02). This reveals that material sources of Lop Nur are relatively richer in potassium and sulfate, while poorer in chloride. Gradual changes of stable isotopic compositions in waters clearly indicate the effect of evaporation on water evolution of the basin. Besides evaporation and weathering of surrounding rocks, wide distribution of chloride type water, which commonly exist in saline springs/brines and seldom exist in other waters, indicates that hydrothermal Ca–Cl brines discharged from deep within the earth join water evolution of the basin.

      PubDate: 2013-08-03T00:32:06Z
  • Geochemistry, provenance and tectonic setting of the Late
           Cambrian–Early Ordovician Seydişehir Formation in the
           Çaltepe and Fele areas, SE Turkey
    • Abstract: Publication date: Available online 2 August 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Mehmet Muzaffer Karadağ
      The major, trace and rare earth element (REE) contents of metapelite (MPL), metapsammite (MPS) and metamarl (MM) samples from the Cambro-Ordovician Seydişehir Formation were analyzed to investigate their provenance and tectonic setting. The MPS, MPL, and MM samples have variable SiO2 concentrations, with average values of 72.36, 55.54, and 20.95wt%, moderate SiO2/Al2O3 ratios (means of 6.88, 3.23, and 3.80), moderate to high Fe2O3 +MgO contents (means of 5.14, 9.55, 3.56wt%), and high K2O/Na2O ratios (means of 3.26, 3.64, 2.90), respectively. On average, the chemical index of alteration (CIA) values of the MPS and the MPL are 65.87 and 71.96, respectively, while the chemical index of weathering (CIW) values are 74.54 and 85.09, respectively. These data record an intermediate to high degree of alteration (weathering) of plagioclase to illite/kaolinite in the samples’ provenance. The chondrite-normalized REE patterns of all the sample groups are similar and are characterized by subparallel light rare earth elements (LREE)-enriched, relatively flat heavy rare earth elements (HREE) patterns with pronounced Eu anomalies (mean of 0.69) and moderate fractionation [average (La/Yb) N =8.7]. Plots of sediments in ternary diagrams of La, Th, Sc and elemental ratios (La/Sc, Th/Sc, Cr/Th, Eu/Eu*, La/Lu, Co/Th, La/Sc and Sc/Th), which are critical for determining provenance, and REE patterns indicate that the metaclastic units of the Seydişehir Formation were derived dominantly from felsic to intermediate magmatic rocks and not from a mafic source. The La–Sc–Th and Th–Sc–Zr/10 ternary diagrams of the Seydişehir Formation are typical of continental island arc/active continental margin tectonic settings. The geologic location and geochemistry of the Seydişehir Formation suggest that it was deposited in an Andean-type retroarc foreland basin during the Late Cambrian–Early Ordovician period. The Neoproterozoic intermediate to felsic magmatic rocks and metaclastic sediments with felsic origins of the Sandıklı–Afyon Basement Complex (SBC) and their equivalent units, which are thought to be overlain by the younger units in the study area, may be the dominant source rocks for the Seydişehir Formation.

      PubDate: 2013-08-03T00:32:06Z
  • Hydrogeochemical zonation for groundwater management in the area with
           diversified geological and land-use setup
    • Abstract: Publication date: Available online 22 July 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Manish Kumar , Roger Herbert Jr. , AL. Ramanathan , M. Someshwar Rao , Kangjoo Kim , Jyoti Prakash Deka , Bhishm Kumar
      Despite its limited aerial extent, the National Capital Territory (NCT) Delhi, India, has diversified geological and topographical setup. A geochemical assessment of prevailing conditions of aquifer underlying the NCT was attempted and further classified into different hydrogeochemical zones on the basis of statistical and analyses and its correlation with land use, geological and climatic setting. Mineral phase study and isotopic analyses were used for the verification of performed clustering. Saturation indices (SI) calculated using the geochemical modelling code PHREEQC were used to distinguish the characteristics of four zones, as saturation states of the water does not change abruptly. Four different hydrogeochemical zones were statistically identified in the area: (1) intermediate (land-use-change-impacted) recharge zone, (2) discharge (agriculture-impacted) zone, (3) recharge (ridge) zone, and (4) recharge floodplain (untreated-discharge-impacted) zone. The distinctiveness of hydro-geochemical zones was further verified using stable isotopic (2H and 18O) signature of these waters. GIS-based flow regime in association with long-term geochemical evidences implied that these zones are being affected by different problems; thus, it necessitates separate environmental measures for their management and conservation. The study suggested that in a diversified urban setup where the complex interactions between anthropogenic activities and normal geochemical processes are functioning, hydrogeochmical zoning based on the integration of various techniques could be the first step towards sketching out the groundwater management plan.

      PubDate: 2013-07-25T23:07:05Z
  • Geochemistry and origin of the Cretaceous sedimentary kaolin deposits, Red
           Sea, Egypt
    • Abstract: Publication date: Available online 18 July 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Hassan M. Baioumy
      This work reports, for the first time, the mineralogical and geochemical characteristics of the Cretaceous sedimentary kaolin deposits in the Red Sea area, Egypt and sheds the light on their source. Mineralogical and geochemical analyses of both bulk deposits and the sand and clay fractions of these deposits indicated that they are composed of kaolinite (average of 75wt.%) and quartz (average of 22wt.%). Traces of anatase (average of 1wt.%) were identified in all kaolin samples, while traces of halite (average of 2wt.%) and hematite (average of 1wt.%) were reported in the majority of the analyzed samples. The clay fractions show relatively high contents of TiO2 (average of 2.1%), Ni (average of 103ppm), Nb (average of 98ppm), Y (average of 67ppm), and Zr (average of 630ppm). Sum of the rare earth elements (ΣREE) in the clay fractions varies between 193 and 352ppm. Chondrite-normalized REE patterns show enrichment of the light REE relative to the heavy REE ((La/Yb) N =9) and negative Eu anomaly (Eu*/Eu=0.67). Major, trace, and rare earth elements geochemistry of the clay fractions from the studied kaolin deposits suggested that these deposits were derived from a mixture of more than source rocks probably a mixture of mafic, granitic, and alkaline rocks. The contribution of granitic rocks was proposed based on the REE pattern and negative Eu anomaly as well as the high Zr and Y contents, while the contribution of mafic rocks to the source was suggested based on the relatively high TiO2 and Ni contents. The abnormally high Nb contents in the clay fractions of the Red Sea kaolin deposits indicated a contribution of alkaline rocks to the source of these deposits. Igneous and metamorphic rocks of different composition belonging to the Arabian-Nubian Shield are located very close to the studied deposits. The monomineralic nature of the Red Sea kaolin deposits as kaolinite, abundance of organic matter, and absence of any marine fossils suggested a non-marine depositional environment of these deposits. Occurrence of halite in the studied deposit is probably due to sea breezes since the studied deposits are located close to the Gulf of Suez.

      PubDate: 2013-07-21T23:06:26Z
  • Note on the isotopic geochemistry of fossil-lacustrine tufas in carbonate
           plateau—A study from Dungul region (SW Egypt)
    • Abstract: Publication date: Available online 17 July 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Kamaleldin M. Hassan
      Lithological, chemical, and stable isotope data are used to characterize lacustrine tufas dating back to pre-late Miocene and later unknown times, capping different surfaces of a Tertiary carbonate (Sinn el-Kedab) plateau in Dungul region in the currently hyperarid south-western Egypt. These deposits are composed mostly of calcium carbonate, some magnesium carbonate and clastic particles plus minor amounts of organic matter. They have a wide range of (Mg/Ca)molar ratios, from 0.03 to 0.3. The bulk-tufa carbonate has characteristic isotope compositions: (δ 13Cmean =−2.49±0.99‰; δ 18Omean =−9.43±1.40‰). The δ 13C values are consistent with a small input from C4 vegetation or thinner soils in the recharge area of the tufa-depositing systems. The δ 18O values are typical of fresh water carbonates. Covariation between δ 13C and δ 18O values probably is a reflection of climatic conditions such as aridity. The tufas studied are isotopically similar to the underlying diagenetic marine chalks, marls and limestones (δ 13Cmean =−2.06±0.84‰; δ 18Omean =−10.06±1.39‰). The similarity has been attributed to common meteoric water signatures. This raises large uncertainties in using tufas (Mg/Ca)molar, δ 13C and δ 18O records as proxies of paleoclimatic change and suggests that intrinsic compositional differences in material sources within the plateau may mask climatic changes in the records.

      PubDate: 2013-07-17T23:19:12Z
  • Soil baseline geochemistry and plant response in areas of complex geology.
           Application to NW Euboea, Greece
    • Abstract: Publication date: Available online 11 July 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Christos Kanellopoulos , Ariadne Argyraki
      A soil and vegetation survey was undertaken in NW Euboea Island, Greece. The objectives of the study were to establish the geochemical baseline of soil and identify the impact of local geology on threshold values of potentially harmful elements. The studied area is characterized by complex geology comprising metamorphic and ultramafic rocks as well as active hot springs. A total of 117 soil samples were collected from 89 sites at depths of 0–25cm and 25–50cm. Eighteen vegetation samples were also collected representing prevalent indigenous perennial species in the region. Soil samples from the present study were enriched in As, Ca, Cu, Mg, Ni with concentrations reaching 233mg/kg, 38%, 336mg/kg, 10.8%, 1560mg/kg respectively. Factor analysis revealed three main factors controlling the chemical composition of soil reflecting the influence of ultramafic rocks (Cr, Ca, Mg, Ni), hot spring deposits (Ca, S, Sr, As) and paedogenesis processes (Fe, Co, V, Mn, Al). The first two of these factors showed significant spatial correlation with the geological features within the study area. Subsequently, baseline concentrations based on statistical and spatial data were estimated within sub-areas reflecting the influence of local geology in soil composition. Concentrations of potentially harmful elements in the plant tissues of indigenous perennial vegetation species showed a wide range of variation from below the detection limit up to 1700mg/kg for Ni in the hyperaccumulator Alyssum chalcidicum demonstrating that plant species have adapted to the stressful conditions caused by high elemental concentrations in soil. The results of this study can be utilized in future studies at areas of similar geology by providing an objective basis for setting realistic threshold values for pollution assessment and remediation.

      PubDate: 2013-07-14T00:36:15Z
  • Mercury in Baltic Sea sediments—Natural background and anthropogenic
    • Abstract: Publication date: Available online 9 July 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Thomas Leipe , Matthias Moros , Aarno Kotilainen , Henry Vallius , Karoline Kabel , Michael Endler , Nicole Kowalski
      In total 27 short and one long sediment core, and 278 surface sediment samples from the Baltic Sea were analyzed for mercury (Hg), and organic carbon contents. Thirteen short cores and the long core were dated by radionuclide methods (210Pb, 137Cs, AMS14C). The dataset allows discriminating between natural and human induced changes on the Hg levels in Baltic Sea sediments. Preindustrial Holocene background concentrations vary between 20 and 50μg Hg per kg dry sediment and are positively correlated with organic carbon changes. Strong human induced pollution is recorded for the second half of the past century and caused high Hg concentrations of up to several hundred μg Hg per kg dry sediment even in Baltic Sea basins. Maximum concentrations are found at industrial and war waste dumping sites (local hot spots). An Hg concentration decreasing trend toward the present day is observed at most coring sites, a result of environmental measures undertaken during the last two decades. At sites where it is possible to calculate Hg fluxes, the natural accumulation rates vary between 2.1 and 5.4μg Hg per m2 per year. Anthropogenically sourced Hg accumulation rates vary in a wide range of 30 and 300μg Hg per m2 per year for the time span of maximum pollution. In areas characterized by discontinuous sedimentation only “inventories” of human sourced Hg expressed as the total amount of deposited Hg (above the natural background) per m2 can be calculated. The inventories of the investigated cores vary in the range of 1 and 8mg Hg per m2. Additionally, influences of sediment dynamics on spatial distribution pattern of Hg concentrations in surface and subsurface sediments are discussed.

      PubDate: 2013-07-09T23:06:49Z
  • Winter and summer monsoonal evolution in northeastern Qinghai-Tibetan
           Plateau during the Holocene period
    • Abstract: Publication date: Available online 25 April 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Bing Liu , Heling Jin , Liangying Sun , Zhong Sun , Zhizhu Su
      Climate change especially moisture condition in the northeastern Qinghai-Tibetan in China are mainly controlled by the strength and variability of Asian winter and summer monsoon. In this paper, we presented the climate record and related winter and summer monsoonal history in Gonghe Basin, northeastern Qinghai-Tibetan Plateau, based on the geochemical indicators (geochemical elements content, i.e., Fe2O3, CaO, Zr and Sr content, and geochemical parameters, i.e., the chemical index of alteration (CIA), Zr/Rb, Rb/Sr, CaO/MgO, SiO2/TiO2 and SiO2/(Al2O3 +Fe2O3) ratio) of the peat deposits and 14C and OSL technologies. The regional temperature and humidity gradually increased in 10.0–8.5calkaBP, accompanied by enhanced summer monsoonal strength and decreased winter monsoonal strength. But climate became cold and dry between 8.5calkaBP and 7.6calkaBP owing to the stronger winter monsoon. During the 7.6–3.8calkaBP, stronger summer monsoon and weaker winter monsoon led to an optimal warm and humid condition, although it had several cold phases. From 3.8calkaBP to 0.5calkaBP, the regional climate tended to be cold and dry, with increasing winter monsoonal strength and decreasing summer monsoonal strength. Thereafter, the relatively warm and humid climate appeared again, due to the stronger summer monsoon. That is to say, the regional climate conditions are mainly related to the winter and summer monsoonal changes. These changes are consistent with palaeoclimatic records (monsoonal model) from the region influenced by the Asian monsoon in eastern China. In addition, nine cold events were recorded: 8.5–7.8calkaBP, 6.1–5.6calkaBP, 5.2–4.8calkaBP, 4.7–4.3calkaBP, 4.1–4.0calkaBP, 3.8–3.4calkaBP, 3.0–2.3calkaBP, 1.4–1.3calkaBP, and 1.0–0.5calkaBP, which are coincident with cold fluctuations in the high and low latitudes of the Northern Hemisphere on a millennial scale, as recorded by lakes, peat sediments, and ice cores in the Qinghai-Tibetan Plateau. In conclusion, Holocene millennial-scale climatic changes in Gonghe Basin were controlled by the dual function of Asian monsoonal changes and global cold fluctuations.

      PubDate: 2013-04-28T23:10:51Z
  • Geochemical and stable isotopic variability within two rivers rising under
           the same mountain, but belonging to two distant watersheds
    • Abstract: Publication date: Available online 9 April 2013
      Source:Chemie der Erde - Geochemistry

      Complementary geochemical and stable isotope investigations of the Gorski Kotar karst aquifer system in western Croatia were obtained for the first time, to answer the question whether both studied rivers drain the same aquifer system or not. The two main rivers, the Kupa and the Rječina, rise under the same mountain range, but belong to two different watersheds (Black Sea and Adriatic Sea). The karst aquifer of Gorski Kotar is a potentially important source of drinking water for two neighboring countries, Croatia and Slovenia (Central and South Europe), and is strongly influenced by both Mediterranean and continental weather conditions. It is a part of the Dinaric karst, which is “locus typicus” for karst worldwide and one of the most typical karst areas in the world. To answer the main question of our research, baseline data were thoroughly collected comprising stable isotopes, concentration of dissolved and total trace metals in water, and multi-elemental analyses of river sediments, together with other physical-chemical parameters (pH, dissolved oxygen, electric conductivity and temperature). Total dissolved solid (TDS) was not measured but estimated as (EC) 0.67. Such multi-technique approach was applied for the first time in the Dinaric karst systems. Multi-elemental analysis of fine sediment fraction (<63μm) of eight samples was performed by ICP-MS. Elemental composition of sediments is quite different in the two studied river valleys, which indicates different origin of their waters. Also, concentrations of selected metals were compared with existing sediment quality criteria and anthropogenic influence is evaluated and discussed. Analytical results of major ions determined in three springs (Kupa spring, Rječina spring, Zvir spring in the City of Rijeka) were used to construct a Piper diagram, which showed that they are of a Ca–Na–HCO3–Cl type. The highest concentration of Mg is present in the Kupa spring, while the highest concentrations of Na and Cl are present in the Zvir spring. Groundwaters are underlain by limestone, less by dolomite and are under a maritime influence. There is a big difference with the main groundwater types reported in North Africa, i.e. in the south Mediterranean Sea, where two main groundwater types are Na–Cl and Ca–SO4–Cl. Concentrations of total and dissolved fractions of trace metals in surface water samples were determined by voltammetry and compared to the European Water Framework Directive values. Concentrations of total Pb and Zn are significantly higher in the water of the Kupa spring than the Rječina spring, suggesting that the karst water bodies of the two springs are not of the same origin. In addition, stable isotope composition (deuterium and oxygen-18) was determined in the spring waters sampled during low and high water conditions. Due to the significant difference in oxygen isotope-ratios it was concluded that the karst reservoir for the Kupa and Rječina springs is not identical. The results obtained from the combination of physical–chemical, geochemical (water and sediment) and isotope multi-technique analyses pointed out that even though the springs of the Kupa and Rječina rivers originate from the same mountain range, they do not drain the same karst aquifer.

      PubDate: 2013-04-12T23:11:43Z
  • Hydrogeochemical characteristics of spring water in the Harz Mountains,
    • Abstract: Publication date: Available online 10 April 2013
      Source:Chemie der Erde - Geochemistry

      Spring water samples of the Harz Mountains were taken in several seasons of 2010, 2011, and 2012. The samples have been analysed for main components (Na+, K+, Ca2+, Mg2+, SO4 2−, Cl−, HCO3 − and NO3 −), trace elements (Fe, Cu, Pb, Zn, Y and REE), DOC, δ18O and δ2H of water. Meteoric water is indicated as the main source of the springs sampled. High precipitation rates lead to a dilution of the measured elemental concentrations. Furthermore, regional differences of rock and water interactions were found. REE concentrations and patterns of the spring waters vary between the distinct geological units and reflect the geochemical characteristics of the surrounding rocks. The actual data compared to measured data from the seventies and nineties of the last century indicate a decrease of the sulphate concentrations in the spring waters which is typical of many European mountain catchments.

      PubDate: 2013-04-12T23:11:43Z
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