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  Subjects -> EARTH SCIENCES (Total: 603 journals)
    - EARTH SCIENCES (447 journals)
    - GEOLOGY (67 journals)
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    - HYDROLOGY (17 journals)
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EARTH SCIENCES (447 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Hybrid Journal   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 8)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 2)
Advances in High Energy Physics     Open Access   (Followers: 11)
Advances In Physics     Hybrid Journal   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 2)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 4)
AMBIO     Hybrid Journal   (Followers: 12)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 1)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 1)
Annals of Geophysics     Full-text available via subscription   (Followers: 9)
Annals of GIS     Hybrid Journal   (Followers: 16)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene Review     Hybrid Journal   (Followers: 1)
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 7)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 9)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 21)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 15)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 17)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 3)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 5)
Atmospheric and Climate Sciences     Open Access   (Followers: 15)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 9)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of Marine Science     Full-text available via subscription   (Followers: 13)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 17)
Bulletin of Volcanology     Hybrid Journal   (Followers: 13)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 11)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 11)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 5)
Contemporary Trends in Geoscience     Open Access  
Continental Journal of Earth Sciences     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 7)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 18)
Cretaceous Research     Hybrid Journal   (Followers: 4)
Cybergeo : European Journal of Geography     Open Access   (Followers: 4)
Developments in Geotectonics     Full-text available via subscription   (Followers: 2)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 195)
Earth Interactions     Full-text available via subscription   (Followers: 8)
Earth Science Research     Open Access   (Followers: 7)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 1)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 11)
Earth System Dynamics     Open Access   (Followers: 5)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 1)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Science     Hybrid Journal   (Followers: 9)
Earthquake Spectra     Full-text available via subscription   (Followers: 12)
Ecohydrology     Hybrid Journal   (Followers: 11)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 10)
Environmental Geology     Hybrid Journal   (Followers: 11)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access  

        1 2 3 4 5 | Last

Journal Cover 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  [2575 journals]   [SJR: 0.612]   [H-I: 23]
  • The geochemistry of platinum group elements in marine oil shale—A
           case study from the Bilong Co oil shale, northern Tibet, China
    • Abstract: Publication date: Available online 4 November 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Xiugen Fu , Jian Wang , Yuhong Zeng , Fuwen Tan , Chen Wenbing , Xinglei Feng
      The Bilong Co oil shale zone is located in the South Qiangtang depression. This zone, together with the Shengli River-Changshe Mountain oil shale zone in the North Qiangtang depression, northern Tibet plateau, represents the potentially largest marine oil shale resource in China. Seventeen samples including oil shale and micritic limestone were collected from the Bilong Co oil shale area to determine the concentrations, distribution patterns, occurrences and origins of platinum group elements (PGEs) in marine oil shale. The oil shale samples from the Bilong Co area exhibit very low total PGE contents ranging from 1.04 to 2.96ng/g with a weighted mean value of 1.686ng/g, while the micritic limestone samples from the Bilong Co area exhibit a little lower PGE value ranging from 0.413 to 1.11ng/g. PGEs in oil shale samples are characterized by high contents in Pd (average 0.79ng/g), Os (average 0.123ng/g) and Pt (average 0.644ng/g) compared with Ru (average 0.068ng/g), Rh (average 0.033ng/g) and Ir (average 0.026ng/g). The highest values for individual PGEs are not uniformly distributed in the section. Clearly, the PGEs are generally enriched in the oil shale samples near the boundary between micritic limestone and oil shale. The individual PGEs in oil shale samples from the Bilong Co area exhibit various modes of occurrence. Ruthenium and Pt occur mainly in pyrite, while Pd is associated mainly with organic matter and Mg-minerals. Rhodium and Os are controlled mainly by pyrite and organic matter. Iridium is present mainly in other Fe-bearing minerals, rather than pyrite. The PGEs in the Bilong Co oil shale are mainly of seawater origin and possibly influenced by terrigenous supply.


      PubDate: 2014-12-17T16:15:58Z
       
  • Stable isotopic signatures of the modern land snail Eremina desertorum
           from a low-latitude (hot) dry desert—A study from the Petrified
           Forest, New Cairo, Egypt
    • Abstract: Publication date: Available online 6 November 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Kamaleldin M. Hassan
      This study was conducted on recent desert samples—including (1) soils, (2) plants, (3) the shell, and (4) organic matter from modern specimens of the land snail Eremina desertorum—which were collected at several altitudes (316–360m above sea level) from a site in the New Cairo Petrified Forest. The soils and shell E. desertorum were analyzed for carbonate composition and isotopic composition (δ18O, δ13C). The plants and organic matter E. desertorum were analyzed for organic carbon content and δ13C. The soil carbonate, consisting of calcite plus minor dolomite, has δ18O values from −3.19 to −1.78‰ and δ13C values −1.79 to −0.27‰; covariance between the two values accords with arid climatic conditions. The local plants include C3 and C4 types, with the latter being dominant. Each type has distinctive bulk organic carbon δ13C values: −26.51 to −25.36‰ for C3-type, and −13.74 to −12.43‰ for C4-type plants. The carbonate of the shell E. desertorum is composed of aragonite plus minor calcite, with relatively homogenous isotopic compositions (δ18Omean =−0.28±0.22‰; δ13Cmean =−4.46±0.58‰). Most of the δ18O values (based on a model for oxygen isotope fractionation in an aragonite-water system) are consistent with evaporated water signatures. The organic matter E. desertorum varies only slightly in bulk organic carbon δ13C values (−21.78±1.20‰) and these values suggest that the snail consumed more of C3-type than C4-type plants. The overall offset in δ13C values (−17.32‰) observed between shell E. desertorum carbonate and organic matter E. desertorum exceeds the value expected for vegetation input, and implies that 30% of carbon in the shell E. desertorum carbonate comes from the consumption of limestone material.


      PubDate: 2014-12-17T16:15:58Z
       
  • Petrology, geochemistry and tectonic significance of serpentinized
           ultramafic rocks from the South Arm of Sulawesi, Indonesia
    • Abstract: Publication date: Available online 8 November 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Adi Maulana , Andrew G. Christy , David J. Ellis
      Serpentinized ultramafic rocks occur in two separate basement complexes in the South Arm of Sulawesi, the Bantimala and Barru Blocks. We present petrographic, mineral chemical and geochemical data for these rocks, and interpret them in terms of petrogenesis and tectonic setting. The rocks of both blocks show strong serpentinization of original anhydrous silicates. The Bantimala ultramafics consist mainly of peridotite (harzburgite and dunite) and clinopyroxenite, with lenses of podiform chromitite. Metamorphism is evidenced by the occurrence of amphibolite-facies tremolite schist. In contrast, the Barru ultramafics consist of harzburgite peridotite and podiform chromitite, which also show an amphibolite-facies overprint that in this case may be related to intrusion by a large dacite/granodiorite body. Whole-rock trace element analyses and spinel compositions show that the Barru harzburgite is depleted relative to primitive mantle, and has had some melt extracted. In contrast, the Bantimala dunite, harzburgite and clinopyroxenite are cumulates. Both are derived from a supra-subduction zone environment, and were obducted during the closure of small back-arc basins. If there has been no rotation of the blocks, then the Bantimala ultramafics were emplaced from an ENE direction, while the Barru ultramafics were emplaced from the WNW. The ultramafic suites from these two blocks are juxtaposed with metamorphic assemblages, which were later intruded by younger volcanics, particularly in the Barru Block.


      PubDate: 2014-12-17T16:15:58Z
       
  • Asteroid (4) Vesta: I. The howardite-eucrite-diogenite (HED) clan of
           meteorites
    • Abstract: Publication date: Available online 18 November 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): David W. Mittlefehldt
      The howardite, eucrite and diogenite (HED) clan of meteorites are ultramafic and mafic igneous rocks and impact-engendered fragmental debris derived from a thoroughly differentiated asteroid. Earth-based telescopic observation and data returned from vestan orbit by the Dawn spacecraft make a compelling case that the asteroid (4) Vesta is the parent asteroid of HEDs, although this is not universally accepted. Diogenites are petrologically diverse and include dunitic, harzburgitic and noritic lithologic types in addition to the traditional orthopyroxenites. Diogenites form the lower crust of Vesta. Cumulate eucrites are gabbroic rocks formed by accumulation of pigeonite and plagioclase from a mafic magma at depth within the crust, while basaltic eucrites are melt compositions that likely represent shallow-level dikes and sills, and flows. Some basaltic eucrites are richer in incompatible trace elements compared to most eucrites, and these may represent mixed melts contaminated by partial melts of the mafic crust. Differentiation occurred within a few Myr of formation of the earliest solids in the Solar System. Evidence from oxygen isotope compositions and siderophile element contents favor a model of extensive melting of Vesta forming a global magma ocean that rapidly (period of a few Myr) segregated and crystallized to yield a metallic core, olivine-rich mantle, orthopyroxene-rich lower crust and basaltic upper crust. The igneous lithologies were subjected to post-crystallization thermal processing, and most eucrites show textural and mineral-compositional evidence for metamorphism. The cause of this common metamorphism is unclear, but may have resulted from rapid burial of early basalts by later flows caused by high effusion rates on Vesta. The observed surface of Vesta is covered by fragmental debris resulting from impacts, and most HEDs are brecciated. Many eucrites and diogenites are monomict breccias indicating a lack of mixing. However, many HEDs are polymict breccias. Howardites are the most thoroughly mixed polymict breccias, yet only some of them contain evidence for residence in the true regolith. Based on the numbers of meteorites, compositions of howardites, and models of magma ocean solidification, cumulate eucrites and their residual ferroan mafic melts are minor components of the vestan crust.


      PubDate: 2014-12-17T16:15:58Z
       
  • Geochemical constraints on the genesis of the Pb–Zn deposit of Jalta
           (northern Tunisia): Implications for timing of mineralization, sources of
           metals and relationship to the Neogene volcanism
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4
      Author(s): Nejib Jemmali , Fouad Souissi , Emmanuel John M. Carranza , Torsten W. Vennemann , Kamen Bogdanov
      The occurrence of Pb–Zn deposits of Jalta district (northern Tunisia) as open space fillings and cements and breccia in the contact zones between Triassic dolostones and Miocene conglomerates along or near major faults provides evidence of the relationship between the mineralization and tectonic processes. Pb isotopes in galena from the deposits yielded average 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 18.821, 15.676 and 38.837, respectively, implying a well-mixed multi-source upper crustal reservoir of metals. Magmatism and compressional tectonism during the Alpine orogeny favored Pb–Zn mineralization in the Jalta district. The enrichment in Pb, Zn, Cd and Co of the Triassic carbonates and enrichments in Pb, Zn and Cd in Triassic clayey shales is associated with hydrothermal alteration around faults. Alunite in the deposit has δ34S values (−2.5 to −1.5‰ VCDT), which could have been formed at and above the water table in a kind of steam-heated environment, where fluids containing H2S mixed with fluids containing K and Al. The H2S could have been produced by TSR of sulfates at high temperature at depth and then leaked upward through deep-seated faults, whereas the K and Al could have been acid-leached from Miocene volcanic rocks.


      PubDate: 2014-12-17T16:15:58Z
       
  • Mineral chemical constraints on the petrogenesis of mafic and intermediate
           volcanic rocks from the Erciyes and Hasandağ volcanoes, Central
           Turkey
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4
      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: 2014-12-17T16:15:58Z
       
  • Genetic classification of magmatic rocks from the Alvand plutonic complex,
           Hamedan, western Iran, based on zircon crystal morphology
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4
      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: 2014-12-17T16:15:58Z
       
  • Holocene climate variation determined from rubidium and strontium contents
           and ratios of sediments collected from the BadainJaran Desert, Inner
           Mongolia, China
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4
      Author(s): Yuanjun Guo , Baosheng Li , Xiaohao Wen , Fengnian Wang , Dongfeng Niu , Yuejun Shi , 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: 2014-12-17T16:15:58Z
       
  • Geochemical features of the Matomb alluvial rutile from the Neoproterozoic
           Pan-African belt, Southern Cameroon
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4
      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 ∼5–25.72) 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 (1–9ppm) in spite of the LREE-abundance (LREE/HREE ∼4–40). 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: 2014-12-17T16:15:58Z
       
  • Geochemistry and behavior of REE in stream sediments close to an old Sn-W
           mine, Ribeira, Northeast Portugal
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4
      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: 2014-12-17T16:15:58Z
       
  • Stable isotope characterization of pedogenic and lacustrine carbonates
           from the Chinese Tian Shan: Constraints on the Mesozoic–Lower
           Cenozoic palaeoenvironmental evolution
    • Abstract: Publication date: Available online 16 December 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): G. Heilbronn , P. Boulvais , E. Marchand , C. Robin , S. Bourquin , L. Barrier , Y. Jia , B. Fu , M. Jolivet
      In the Mesozoic–Cenozoic continental deposits of the Tian Shan area, two main levels containing pedogenic carbonates have been identified on both the southern and northern foothills of the range: one in the Upper Jurassic series and one in the Upper Cretaceous–Lower Palaeocene series. In order to reconstruct the palaeoenvironmental and palaeotopographic characteristics of the Tian Shan area during these two periods, we measured the oxygen and carbon isotope composition of these pedogenic carbonates (calcrete and nodules). The stable isotope compositions are homogeneous: most δ18O values are between 21 and 25‰ and most δ13C values are between −4 and −6‰. No distinction can be made between the calcrete and nodule isotopic compositions. The constancy of isotopic values across the Tian Shan is evidence of a development of these calcification features in similar palaeoenvironmental conditions. The main inference is that no significant relief existed in that area at the Cretaceous−Palaeogene boundary, implying that most of the present relief developed later, during the Cenozoic. In addition to the pedogenic carbonates, few beds of limestones interstratified in the Jurassic series of the southern foothills display oxygen and carbon isotope compositions typical of lacustrine carbonates, ruling out brackish water incursion at that period in the region.


      PubDate: 2014-12-17T16:15:58Z
       
  • Editorial board members
    • Abstract: Publication date: December 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 4




      PubDate: 2014-12-17T16:15:58Z
       
  • Impact features of enstatite-rich meteorites
    • Abstract: Publication date: Available online 11 December 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Alan E. Rubin
      Enstatite-rich meteorites include EH and EL chondrites, rare ungrouped enstatite chondrites, aubrites, a few metal-rich meteorites (possibly derived from the mantle of the aubrite parent body), various impact-melt breccias and impact-melt rocks, and a few samples that may be partial-melt residues ultimately derived from enstatite chondrites. Members of these sets of rocks exhibit a wide range of impact features including mineral-lattice deformation, whole-rock brecciation, petrofabrics, opaque veins, rare high-pressure phases, silicate darkening, silicate-rich melt veins and melt pockets, shock-produced diamonds, euhedral enstatite grains, nucleation of enstatite on relict grains and chondrules, low MnO in enstatite, high Mn in troilite and oldhamite, grains of keilite, abundant silica, euhedral graphite, euhedral sinoite, F-rich amphibole and mica, and impact-melt globules and spherules. No single meteorite possesses all of these features, although many possess several. Impacts can also cause bulk REE fractionations due to melting and loss of oldhamite (CaS) – the main REE carrier in enstatite meteorites. The Shallowater aubrite can be modeled as an impact-melt rock derived from a large cratering event on a porous enstatite chondritic asteroid; it may have been shock melted at depth, slowly cooled and then excavated and quenched. Mount Egerton may share a broadly similar shock and thermal history; it could be from the same parent body as Shallowater. Many aubrites contain large pyroxene grains that exhibit weak mosaic extinction, consistent with shock-stage S4; in contrast, small olivine grains in some of these same aubrites have sharp or undulose extinction, consistent with shock stage S1 to S2. Because elemental diffusion is much faster in olivine than pyroxene, it seems likely that these aubrites experienced mild post-shock annealing, perhaps due to relatively shallow burial after an energetic impact event. There are correlations among EH and EL chondrites between petrologic type and the degree of shock, consistent with the hypothesis that collisional heating is mainly responsible for enstatite-chondrite thermal metamorphism. Nevertheless, the apparent shock stages of EL6 and EH6 chondrites tend to be lower than EL3-5 and EH3-5 chondrites, suggesting that the type-6 enstatite chondrites (many of which possess impact-produced features) were shocked and annealed. The relatively young Ar–Ar ages of enstatite chondrites record heating events that occurred long after any 26Al that may have been present initially had decayed away. Impacts remain the only plausible heat source at these late dates. Some enstatite meteorites accreted to other celestial bodies: Hadley Rille (EH) was partly melted when it struck the Moon; Galim (b), also an EH chondrite, was shocked and partly oxidized when it accreted to the LL parent asteroid. EH, EL and aubrite-like clasts also occur in the polymict breccias Kaidun (a carbonaceous chondrite) and Almahata Sitta (an anomalous ureilite). The EH and EL clasts in Kaidun appear unshocked; some clasts in Almahata Sitta may have been extensively shocked on their parent bodies prior to being incorporated into the Almahata Sitta host.


      PubDate: 2014-12-17T16:15:58Z
       
  • Geochemistry of the Eocene Jijuntun Formation oil shale in the Fushun
           Basin, northeast China: Implications for source-area weathering,
           provenance and tectonic setting
    • Abstract: Publication date: Available online 24 September 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Rong Liu , Zhaojun Liu , Pingchang Sun , Yinbo Xu , Dongqing Liu , Xiaohong Yang , Chao Zhang
      Within the fault-bound Fushun Basin of northeastern China, the Eocene Jijuntun Formation hosts extensive deposits of thick lacustrine oil shale. Systematic sampling and geochemical analysis of these deposits has revealed that the parent rocks of the oil shale underwent moderate chemical weathering; and that its mineralogy and trace and rare earth element geochemistry were mainly controlled by parent rock composition, with no synsedimentary changes in the source terrain. Based on source rock and tectonic setting discrimination diagrams, we concluded that the parent rocks of the oil shale were mostly basalts of the Paleogene Laohutai Formation. These basalts originated in a continental back arc environment and contain abundant nutrient elements such as Fe, P, Ni, Cu and Zn, all of which are essential for the growth of aquatic photoautotrophs in lakes. Continuous, high primary productivity in the Jinjuntun lacustrine depocentre, combined with a stable tectonic setting and underfilled sedimentary environment, were key factors in the genesis of its oil shale.


      PubDate: 2014-09-25T12:44:16Z
       
  • Chondrule size and related physical properties: A compilation and
           evaluation of current data across all meteorite groups
    • Abstract: Publication date: Available online 20 September 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Jon M. Friedrich , Michael K. Weisberg , Denton S. Ebel , Alison E. Biltz , Bernadette M. Corbett , Ivan V. Iotzov , Wajiha S. Khan , Matthew D. Wolman
      The examination of the physical properties of chondrules has generally received less emphasis than other properties of meteorites such as their mineralogy, petrology, and chemical and isotopic compositions. Among the various physical properties of chondrules, chondrule size is especially important for the classification of chondrites into chemical groups, since each chemical group possesses a distinct size-frequency distribution of chondrules. Knowledge of the physical properties of chondrules is also vital for the development of astrophysical models for chondrule formation, and for understanding how to utilize asteroidal resources in space exploration. To examine our current knowledge of chondrule sizes, we have compiled and provide commentary on available chondrule dimension literature data. We include all chondrite chemical groups as well as the acapulcoite primitive achondrites, some of which contain relict chondrules. We also compile and review current literature data for other astrophysically-relevant physical properties (chondrule mass and density). Finally, we briefly examine some additional physical aspects of chondrules such as the frequencies of compound and “cratered” chondrules. A purpose of this compilation is to provide a useful resource for meteoriticists and astrophysicists alike.


      PubDate: 2014-09-21T11:05:46Z
       
  • The use of water-extractable Cu, Mo, Zn, As, Pb concentrations and
           automated mineral analysis of flue dust particles as tools for impact
           studies in topsoils exposed to past emissions of a Cu-smelter
    • Abstract: Publication date: October 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 3
      Author(s): Ursula Kelm , Mario Avendaño , Eduardo Balladares , Sonia Helle , Teemu Karlsson , Marcos Pincheira
      An exploratory study has been conducted to test the utility of automated mineral analysis observations to identify flue dust particles in topsoils exposed for several decades to emissions of a copper smelter. The methods used are readily available in mining countries. To identify the most impacted sites, the Cu, Zn, Pb, Mo and As levels in water and diluted sulphuric acid extractions of four topsoil size fractions (833–495μm, 246–148μm; 74–38μm; <38μm) were analysed. X-ray diffraction analyses were used to demonstrate the mineralogical degradation of smectite phases when approaching the smelter. Flue dust particles in different states of conservation in topsoils were directly observed by scanning electron microscopy (SEM) aided by energy dispersive detection of X-rays. Qemscan® scanning of dispersed topsoil preparations (10,000 particles) pinpoints smelter particles by their density; flue dust pearls can be tracked by sorting particles according to their sphericity, clearly identifying them as pyrometallurgical products. When sorting soil particles by mineral groups (e.g. sulphides), an increase in this phase group can be observed when approaching the smelter. SEM resolution limits observations to particles larger than 2–3μm. Smaller particles can be observed by transmission electron microscopy, although observer experience and the availability of equipment time are essential as is the case for SEM.


      PubDate: 2014-09-04T06:52:46Z
       
  • Historical mercury trends recorded in sediments from the Laguna del Plata,
           Córdoba, Argentina
    • Abstract: Publication date: October 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 3
      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: 2014-09-04T06:52:46Z
       
  • Formation of solid bituminous matter in pegmatites: Constraints from
           experimentally formed organic matter on microporous silicate minerals
    • Abstract: Publication date: October 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 3
      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: 2014-09-04T06:52:46Z
       
  • Editorial board members
    • Abstract: Publication date: October 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 3




      PubDate: 2014-09-04T06:52:46Z
       
  • Geochemical and Sr–Nd isotopic characteristics of Murgul (Artvin)
           volcanic rocks in the Eastern Black Sea Region (Northeast Turkey)
    • Abstract: Publication date: October 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 3
      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: 2014-09-04T06:52:46Z
       
  • 100 Jahre Chemie der Erde 1914–2014 SEMPER BONIS ARTIBUS
    • Abstract: Publication date: Available online 14 August 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Klaus Heide



      PubDate: 2014-08-15T05:23:24Z
       
  • The effect of valence state and site geometry on Cr L3,2 electron
           energy-loss spectra of Cr-bearing oxidic compounds
    • Abstract: Publication date: Available online 10 August 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Emil Stoyanov , Falko Langenhorst
      Chromium L 3,2 energy loss near-edge structures (ELNES) of nine chromium compounds were measured in a transmission electron microscope to study the effect of valence state and site geometry of chromium on spectral features. The compounds studied represent a set of standards with given valence state and coordination. The chromium coordination is either octahedral or tetrahedral with different degree of distortion. The distortion of polyhedra results in a loss of the fine detail of spectral features in Cr L 3,2 ELNES spectra. The effect of valence state manifests in a systematic chemical shift of the ELNES spectra by about 2eV per oxidation state for octahedrally coordinated Cr and 0.4–1.4eV per oxidation state for tetrahedrally coordinated Cr. On the basis of collected Cr L 3,2 ELNES spectra we propose a simple quantification technique for the determination of chromium oxidation state in oxidic compounds which is independent of the coordination.


      PubDate: 2014-08-11T04:56:32Z
       
  • Celebrating the centennial birthday of Chemie der Erde –
           Geochemistry
    • Abstract: Publication date: Available online 30 July 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Falko Langenhorst



      PubDate: 2014-08-01T03:53:20Z
       
  • Relationships between major and trace elements during weathering processes
           in a sedimentary context: Implications for the nature of source rocks in
           Douala, Littoral Cameroon
    • Abstract: Publication date: Available online 21 June 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Estelle Ndome Effoudou-Priso , Vincent Laurent Onana , Likiby Boubakar , Véronique Kamgang Kabeyene Beyala , Georges Emmanuel Ekodeck
      In Douala (Littoral Cameroon), the Cretaceous to Quaternary formation composed of marine to continental sediments are covered by ferrallitic soils. These sediments and soils have high contents of SiO2 (≥70.0wt%), intermediate contents of Al2O3 (11.6–28.4wt%), Fe2O3 (0.00–20.5wt%) and TiO2 (0.04–4.08wt%), while K2O (≤0.18wt%), Na2O (≤0.04wt%), MgO (≤0.14wt%) and CaO (≤0.02wt%) are very low to extremely low. Apart from silica, major oxides and trace elements (REE included) are more concentrated in the fine fraction (<62.5μm) whose proportions of phyllosilicates and heavy minerals are significant. The close co-associations between Zr, Hf, Th and ∑REE in this fraction suggest that REE distribution is controlled by monazite and zircon. CIA values indicate intense weathering. Weathering products are characterized by the association Al2O3 and Ga in kaolinite; the strong correlation between Fe2O3 and V in hematite and goethite; the affinity of TiO2 with HFSE (Hf, Nb, Th, Y and Zr) in heavy minerals. The ICV values suggest mature sediments. The PCI indicates a well-drained environment whereas U/Th and V/Cr ratios imply oxic conditions. La/Sc, La/Co, Th/Cr, Th/Sc and Eu/Eu* elemental ratios suggest a source with felsic components. Discrimination diagrams are consistent with the felsic source. The REE patterns of some High-K granite and granodiorite of the Congo Craton resemble those of the samples, indicating that they derive from similar source rocks.


      PubDate: 2014-07-28T03:38:29Z
       
  • Compositional signatures of SSZ-type peridotites from the northern
           Vourinos ultra-depleted upper mantle suite, NW Greece
    • Abstract: Publication date: Available online 25 June 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Argyrios N. Kapsiotis
      The northern Vourinos massif, located in the Dinarides-Hellenides mountain belt in the Balkan Peninsula, forms a section of the so-called Neotethyan ophiolitic belt in the Alpine-Himalayan orogenic system. It is comprised mainly of a well-preserved mantle sequence, dominated by voluminous massive harzburgite with variable clinopyroxene and olivine modal abundances, accompanied by subordinate coarse- and fine-grained dunite. The harzburgite rock varieties are characterized by high Cr# [Cr/(Cr+Al)] values in Cr-spinel (0.47–0.74), elevated Mg# [Mg/(Mg+Fe2+)] in olivine (0.90–0.93), low Al2O3 content in clinopyroxene (≤1.82wt.%) and low average bulk-rock concentrations of CaO (0.52wt.%) and Al2O3 (0.40wt.%), which are indicative of their refractory nature. In addition, dunite-type rocks display even more depleted compositions, containing Cr-spinel and olivine with higher Cr# (0.76–0.84) and Mg# (0.91–0.94), respectively. They also display extremely low average abundances of CaO (0.13wt.%) and Al2O3 (0.15wt.%). The vast majority of the studied peridotites are also strongly depleted in REE. Simple batch and fractional melting models are not sufficient to explain their ultra-depleted composition. Whole-rock trace element abundances of the northern Vourinos mantle rocks can be modeled by up to 22–31% closed-system non-modal dynamic melting of an assumed primitive mantle (PM) source having spinel lherzolite composition. The highly depleted compositional signatures of the investigated peridotites indicate that they have experienced hydrous melting in the fore-arc mantle region above a SSZ. This intense melting event was responsible for the release of arc-related melts from the mantle. These melts reacted with the studied peridotites causing incongruent melting of pyroxenes followed by considerable olivine and Cr-spinel addition in terms of cryptic metasomatism. This later metasomatic episode has obscured any geochemical fingerprints indicative of an early mantle melting event in a MOR setting. The lack of any MOR-type peridotites in the northern Vourinos depleted mantle suite is quite uncommon for SSZ-type Neotethyan ophiolites.


      PubDate: 2014-07-28T03:38:29Z
       
  • 40Ar/39Ar dating of ignimbrites and plinian air-fall layers from
           Cappadocia, Central Turkey: Implications to chronostratigraphic and
           Eastern Mediterranean palaeoenvironmental record
    • Abstract: Publication date: Available online 30 June 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Petra Lepetit , Lothar Viereck , John D.A. Piper , Masafumi Sudo , Ali Gürel , Ibrahim Çopuroğlu , Manuela Gruber , Bernhard Mayer , Michael Koch , Orhan Tatar , Halil Gürsoy
      Magmatism forming the Central Anatolian Volcanic Province of Cappadocia, central Turkey, records the last phase of Neotethyan subduction after ∼11Ma. Thirteen large calc-alkaline ignimbrite sheets form marker bands within the volcano-sedimentary succession (the Ürgüp Formation) and provide a robust chronostratigraphy for paleoecologic evaluation of the interleaved paleosols. This paper evaluates the chronologic record in the context of the radiometric, magnetostratigraphic and lithostratigraphic controls. Previous inconsistencies relating primarily to K/Ar evidence were reason for the initiation of an integrated study which includes 40Ar/39Ar dating, palaeomagnetic and stratigraphic evidence. The newly determined 40Ar/39Ar-ages (Lepetit, 2010) are in agreement with Ar/Ar and U/Pb data meanwhile published by Pauquette and Le Pennec (2012) and Aydar et al. (2012). The 40Ar/39Ar-ages restrict the end of the Ürgüp Formation to the late Miocene. The paleosol sequence enclosed by the ignimbrites is thus restricted to the late Miocene, the most intense formation of pedogene calcretes correlating with the Messinian Salinity Crisis.


      PubDate: 2014-07-28T03:38:29Z
       
  • Stability and crystal chemistry of iron-bearing dense hydrous magnesium
           silicates
    • Abstract: Publication date: Available online 17 July 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Geertje Ganskow , Falko Langenhorst
      Dense hydrous magnesium silicates (DHMS) are supposed to be key phases in planetary water cycles because of their ability to carry water to deep mantle regions in subduction slab environments. In order to understand water cycles in iron-enriched planetary systems such as Mars knowledge of the water content and stability of iron-bearing DHMS is required. Iron-bearing DHMS were synthesized based on two starting compositions, MgFeSiO4 +9.5wt% H2O system and a simple hydrous Martian mantle composition containing Fe, Mg, Al and Si+12.35wt% H2O (hydrous FMAS system). Compared to literature data on phase D, iron-bearing phase D shows analogous variations in water contents as Mg-phase D but appears to be stable at higher temperatures than Mg-phase D for both starting compositions used in this study. Iron-bearing superhydrous phase B contains up to 7wt% H2O and shows an extended thermal stability in the hydrous FMAS system. The high-temperature stability of iron-bearing DHMS with a Mars-like bulk composition indicates that these hydrous phases could host significant amounts of water at core-mantle boundary conditions (1500°C and 23GPa) in a hydrous Martian mantle.


      PubDate: 2014-07-28T03:38:29Z
       
  • Siderophile elements in chondrules of CV chondrites
    • Abstract: Publication date: Available online 18 July 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Herbert Palme , Bernhard Spettel , Dominik Hezel
      New bulk compositional data for 34 Allende chondrules are presented. Whole chondrules were analyzed by instrumental neutron activation analysis (INAA). The new data set is evaluated together with older INAA data on Allende chondrules and recent INAA data on Mokoia chondrules. The Ni/Co ratios of 200 chondrules are close to the CI- or solar ratio. The chondritic Ni/Co ratios require an unfractionated chondritic metal source and set a limit to the fraction of metal lost from molten chondrules. The bulk chondrule Fe/Ni and Fe/Co ratios are more variable but on average chondritic. Iridium and other refractory metals have extremely variable concentrations in chondrules. High Ir chondrules have chondritic Ir/Sc ratios. They are dominated by CAI (Ca,Al-rich inclusion) components. Low Ir chondrules have approximately chondritic Ir/Ni ratios reflecting mixing with chondritic metal. In low Ir chondrules Ir correlates and in high Ir chondrules Ir does not correlate with Ni or Co. A large fraction of Ir may have entered chondrules in variable amounts as tiny grains of refractory metal alloys. Most Allende chondrules have Ir/Sc ratios below bulk meteorite ratios. Matrix must have a complementary high Ir/Sc ratio, as bulk Allende has approximately chondritic Ir/Sc ratio. Similarly, the high average Ir/Ni ratios of Allende chondrules must be balanced by low Ir/Ni ratios in matrix to obtain the bulk Allende Ir/Ni ratio, which is close to the average solar system ratio. More recent data on single chondrules from Allende by ICP-MS (Inductively Coupled Plasma Mass Spectrometry) and ICP-OES (Inductively Coupled Optical Emission Spectrometry) show the same trends as the INAA data discussed here.


      PubDate: 2014-07-28T03:38:29Z
       
  • Isotope geochemistry of Swan Lake Basin in the Nebraska Sandhills, USA:
           Large 13C enrichment in sediment-calcite records
    • Abstract: Publication date: Available online 1 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Kamaleldin M. Hassan
      This study presents isotope geochemical analyses conducted on water column samples and core sediments collected from the Swan Lake Basin. Water analyses include the dissolved methane (CH4) content and the ratio of carbon-13 to carbon-12 (δ 13C) in dissolved inorganic carbon (DIC). The core sediments – sandy muds containing inorganic calcite, organic matter, and opal phases±ostracods – were examined by X-ray diffraction, dated by radiocarbon (14C), analyzed for wt% organic carbon, wt% organic nitrogen, wt% organic matter, wt% calcite, δ 13C of bulk-sediment insoluble organic matter (kerogen), 18O:16O ratio (δ 18O) and δ 13C of bulk and ostracod calcite. Of particular significance is the large enrichment in carbon-13 (δ 13C=+4.5 to +20.4‰ V-PDB) in the calcite of these sediments. The 13C-enriched calcite is primarily formed from DIC in the water column of the lake as a result of the following combined processes: (i) the incorporation of 13C enriched residual carbon dioxide (CO2) after partial reduction to CH4 in the sediments and its migration into the water column-DIC pool; (ii) the preferential assimilation of 12C by phytoplankton during photosynthesis; (iii) the removal of 13C-depleted CH4 by ebullition and of organic matter by sedimentation and burial. The 13C enrichment was low between 3624 and 2470yr BP; high between 2470 and 1299yr BP; and moderate since 1299yr BP. Low 13C enrichment was formed under low water-column carbon levels while higher ones were formed under elevated rates of biomass and calcite deposition. These associations seem to imply that biological productivity is the main reason for carbon-13 enrichments.


      PubDate: 2014-06-14T19:10:38Z
       
  • Spherulitic omphacite in pseudotachylytes: Microstructures related to fast
           crystal growth from seismic melt at eclogite-facies conditions
    • Abstract: Publication date: Available online 2 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Kilian Pollok , Florian Heidelbach , Timm John , Falko Langenhorst
      The microstructures and microtexture of omphacite spherulites from an eclogite-facies pseudotachylyte from central Zambia was studied by electron backscattered diffraction and transmission electron microscopy. The spherulitic growth is characteristic for fast growth rates at high undercoolings resulting from quenching a melt of seismic origin to the eclogite-facies conditions. Its preservation constrains that no significant deformation was present after the seismic event and during uplift. The analysis of grain misorientations in spherulites indicates – in addition to the overall radial alignment of grains – that crystallization took place in a highly viscous medium, which does not allow grain reorientation during growth. The microstructure of omphacite is diverse and ambiguous: Grain contacts appear both curved and with 120° triple junctions with few recrystallized grains. Dislocations are frequent, but heterogeneously distributed and occur in dislocations networks, subgrain boundaries and as free dislocations with locally high densities. Planar defects (chain multiplicity faults parallel (010) ending at partial dislocations) are abundant, while twinning parallel to (100) is rare. Anti-phase domains with variable domain sizes within a single grain and the disappearance of domain walls around the planar defects constrain that most of the microstructure must be formed during or shortly after crystallization. Omphacite microstructures are commonly discussed as result of deformational stresses due to a tectonic forcing. Here, we hypothesize that thermal stress during growth also can provide a feasible explanation for this melt-grown omphacite followed with partial recovery under static conditions. The observation does not exclude repeated stress loading of the shear veins in general, but suggest that only the latest seismic event is preserved in the studied samples as fine-grained texture of the spherulites. Moreover, anti-phase domain sizes constrain that the rock must be uplifted rather shortly after the seismic event.


      PubDate: 2014-06-14T19:10:38Z
       
  • Photoluminescence of synthetic titanite-group pigments: A rare quenching
           effect
    • Abstract: Publication date: Available online 9 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Lutz Nasdala , Teodora Stoyanova Lyubenova , Michael Gaft , Manfred Wildner , Wilfredo Diegor , Christian Petautschnig , Dominik Talla , Christoph Lenz
      Chromium-doped titanite and malayaite samples, which were synthesised to evaluate their performance as ceramic pigments, show remarkable photoluminescence behaviour. Emissions of centres related to traces of trivalent rare-earth elements (REE) are observed exclusively from chromium-free samples. Their Cr-doped analogues (containing the same REEs on the same concentration levels), in contrast, only show broad-band Cr3+ emission whereas all REE emissions are suppressed. This behaviour is assigned to quenching of REE emissions by chromium centres (i.e., REE3+ →Cr3+ energy transfer).


      PubDate: 2014-06-14T19:10:38Z
       
  • Lithium elemental and isotopic variations in rock-melt interaction
    • Abstract: Publication date: Available online 13 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Ben-Xun Su , Hong-Fu Zhang , Etienne Deloule , Nathalie Vigier , Patrick Asamoah Sakyi
      Despite the occurrence of highly variable lithium (Li) elemental distribution and isotopic fractionation in mantle mineral, the mechanism of Li heterogeneity and fractionation remains a controversial issue. We measured Li contents and isotopic compositions of olivine and clinopyroxene xenocrysts and phenocrysts from kamafugite host lavas, as well as minerals in melt pockets occurring as metasomatic products in peridotite xenoliths from the Western Qinling, central China. The olivine xenocrysts in the kamafugites show compositional zonation. The cores have high Mg# (100×Mg/(Mg+Fe); 91.0–92.2) and Li abundances (5.63–21.7ppm), low CaO contents (≤0.12wt%) and low δ 7Li values (−39.6 to −6.76‰), which overlap with the compositional ranges of the olivines in the melt pockets as well as those in peridotite xenoliths. The rims of the olivine xenocrysts display relatively low Mg# (85.9–88.2), high CaO contents (0.19–0.38wt%) and high δ 7Li values (18.3–26.9‰), which are comparable to the olivine phenocrysts (Mg#: 86.4–87.1; CaO: 0.20–0.28wt%; Li: 12.4–36.8ppm; δ 7Li: 18.1–26.0‰) and the silicate-melt metasomatized olivines. The clinopyroxene phenocrysts and clinopyroxenes in the melt pockets have no distinct characteristics with respect to the Li abundances and δ 7Li values, but show higher and lower CaO contents, respectively, than the clinopyroxenes from silicate and carbonatite metasomatized samples. These features indicate that Li concentration and isotopic signatures of the cores of the xenocrysts recorded carbonatite melt-peridotite reaction (carbonatite metasomatism) at mantle depth, and the variations in the rims probably resulted from xenocryst–host magma interaction during ascent. Our results reveal that the interaction with carbonatite and silicate melts gave rise to an increase in Li abundance in minerals of peridotite xenoliths at mantle depth or during transportation. In terms of δ 7Li, the carbonatite and silicate melts produced remarkably contrasting δ 7Li variations in olivine. Based on the systematic variations of Li abundances and Li isotopes in olivines, we suggest that the δ 7Li value of olivine is a more important indicator than that of clinopyroxene in discriminating carbonatite and silicate melt interaction agents with peridotites.


      PubDate: 2014-06-14T19:10:38Z
       
  • Geogenic versus anthropogenic geochemical influence on trace elements
           contents in soils from the Milazzo Peninsula
    • Abstract: Publication date: Available online 14 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Joëlle Duplay , Khadija Semhi , Morgane Mey , Antonia Messina , Gaetana Quaranta , Fabienne Huber , Amélie Aubert
      Milazzo Peninsula soils and substrates are extremely variable, composed of acidic, mafic and ultramafic metamorphic rocks, carbonatic sedimentary rocks, and sometimes volcanic rocks, thus contributing to a mixed influence on their chemical composition. Moreover, the region is highly polluted due to atmospheric releases from anthropogenic activities, such as refinery industry. In addition, emissions of airborne particles from volcanic eruptions are also likely to fall to the ground and provide trace elements to the soils. The purpose of this study is to distinguish between anthropogenic and geogenic sources contributing to the concentrations of metals in soils by studying their distribution in major and trace elements in relation to substrates. As regards geogenic sources, the major elements composition of soils comes firstly from metamorphic rocks, secondly from carbonates, and to a minor extent from volcanic rocks. Enrichment factors calculations relative to substrate rocks, and using Th as reference element, show that the soils are enriched in As, Pb, Zn, and Ni. Rare earth elements (REEs) patterns normalized to substrate rocks exhibit enrichment in light REEs and a positive anomaly in Gd, indicating anthropogenic contributions in the soil composition. REE ratios and trace elements were plotted to investigate the relationships between anthropogenic sources and substrates in soils compositions. The graphs of La/Ni vs La/Gd and La/Ce vs La/Nd show that soils plot on a line toward substrate rocks on one side, and toward an end member which is represented by a spent catalyst and atmospheric particles emitted by refinery activities. Plots of La vs Cr, and V vs La show similar trends, whereas plots of Zn vs Ni and Pb vs V suggest that another end member, which is unidentified, contributes to soil enrichment in Zn and Pb. A binary mixing model applied to the most Zn enriched soil suggests that anthropogenic inputs from refinery emissions may have contributed to 16% of the anomalies in La/Gd. These results suggest that the trace element composition of Milazzo's peninsula soils partly bears the signature of atmospheric emissions of the refinery.


      PubDate: 2014-06-14T19:10:38Z
       
  • Thermal waters in the Lower Yarmouk Gorge and their relation to
           surrounding aquifers
    • Abstract: Publication date: Available online 14 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): C. Siebert , P. Möller , S. Geyer , S. Kraushaar , P. Dulski , J. Guttman , A. Subah , T. Rödiger
      Sources and mineralization of groundwaters from Cretaceous A7/B2 and B4 limestone aquifers in the Golan and Ajloun Heights are derived from conjoint discussion of stable isotopes of water and sulphate, major ion chemistry, rare earth distribution patterns and the (hydro)geological setting. Isotope fractionation of precipitation was used to derive elevation and continental influence of recharge areas. Positive shift of δ 18O and δ 2H occur due to evaporation before replenishment and the interaction with basalts. Major infiltration areas for Golan Heights are the limy foothills of the Mt. Hermon and for the Ajloun Heights the Plateau itself. To a less degree, precipitation infiltrates also the basaltic catchments. Groundwaters are mineralized by water/rock (i) variably altered limestones by diagenesis, (ii) evaporates and seawater brines enclosed in limestone matrix and (iii) locally occurring basaltic intrusiva. In the Yarmouk Gorge, a deep-seated brine of the Ha’on type ascends and mixes with the fresh shallow groundwater. Contrasting the macro chemical composition, REY distribution patterns indicate the lithology of the recharge areas. Infiltration over basalts results in REY patterns distinctly different to those derived from limy catchments. REY and isotope fingerprints prove that water from the Syrian Hauran Plateau is recharging springs and wells in the lowermost Yamouk gorge. The basaltic cover of the Golan Heights is of minor importance for recharge of the underlying A7/B2 aquifer, which becomes recharged at the foothills of Mt. Hermon and gets confined southwards. Even the wells in the basaltic cover receive water from the underlying limestone aquifer. Anomalous heat flux near the Yarmouk gorge and locally in the western escarpment of the Ajloun may be produced by ascending fluids from greater depth and/or by basaltic intrusions.


      PubDate: 2014-06-14T19:10:38Z
       
  • Constrains from magmatic and hydrothermal epidotes on crystallization of
           granitic magma and sulfide mineralization in Paleoproterozoic Malanjkhand
           Granitoid, Central India
    • Abstract: Publication date: Available online 16 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Dinesh Pandit , Mruganka K. Panigrahi , Takeru Moriyama
      The Paleoproterozoic Malanjkhand Granitoid (MG) pluton in the Central India was studied to constrain the depth of emplacement, upward magma transport rate, and quantification of physicochemical condition of sulfide deposition. In this study, the magmatic and hydrothermal epidotes are of two varieties, reported from a mineralized granitoid. In the MG, composition of magmatic epidotes (pistachite – Ps: 21.6–31.1mole%) and hydrothermal epidotes (Ps: 22.6–31.1mole%) are overlapping in terms of mole percent of pistachite component. It does not provide any significant discrimination between the two varieties. Presence of oscillatory zoning in magmatic epidotes indicates that there was cyclic change in the oxygen fugacity or bulk composition of granitic magma during crystallization. Al-in-hornblende barometry indicates that the MG crystallized under 2–5.6kbar pressure and high oxidation state (FMQ-HM) conditions, inferred from Fe/(Fe+Mg) ratio in hornblende (0.36–0.51) over wide range of temperature (800–650°C). Partial dissolution of epidote indicates an average 6 years time that corresponds to upward transport rates 0.45km/year for magma migration in the crust. Rapid upward magma migration in most cases was probably through dyke mechanism, which is also the most appropriate model to understand the emplacement of granitic magma responsible for the formation of Malanjkhand pluton. In the Malanjkhand ore deposit, hydrothermal epidotes associated with major sulfide phases (chalcopyrite and pyrite) suggest that they equilibrated with the mineralizing ore fluid. Hydrothermal epidotes were formed over a wide range of temperature (147–424°C). From mineral–fluid equilibria modeling it was inferred that low to moderate temperature, moderate to high f O 2 (>HM buffer) and low f S 2 conditions were favorable for formation of hydrothermal epidotes. Interaction between hydrothermal epidote with mineralizing ore fluid in the wall rock would raise the log ( a Ca 2 + / a H + 2 ) ratio that brings a fall in pH values, followed by potassic alteration, which promotes the deposition of sulfide ores at Malanjkhand. Sulfide mineralization in the MG represents a unique Paleoproterozoic granite ore system.


      PubDate: 2014-06-14T19:10:38Z
       
  • Formation of helictite in the cave Dragon Belly (Sardinia,
           Italy)—Microstructure and incorporation of Mg, Sr, and Ba
    • Abstract: Publication date: Available online 17 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Peter Onuk , Martin Dietzel , Christoph Anton Hauzenberger
      In the Dragon Belly cave helictites, a special type of irregular speleothem, are found, which grew on stalactites in all vertical and horizontal directions without any affinity to gravity. Microstructural and mineralogical analyses of this stalactite–helictite system indicate that its evolution is initiated by clogging of the central stalactite channel at its tip, probably when the cave was flooded by muddy water. Clogging caused the formation of secondary channels (≈0.2mm in diameter) for water passage through the outer surface of the stalactite, where helictites start to grow. The secondary channel passes into the central channel of the helictite. The helictites consist of stacked idiomorphic calcite crystals with uniform orientation. Growth of calcite is essentially controlled by water transfer through the central channel and via canalicules (narrow channels of ≈0.05mm in diameter) following the crystal boundaries of the calcite mesocrystal induced by capillary hydrostatic forces. At straight parts of the helictites calcite crystals are almost uniform in size, but at bended parts crystals are significantly smaller inside (≤0.1mm in length) than outside of the bend (≤0.5mm). It is proposed that the difference in calcite volume (larger crystals) vs. the inside of the bend leads to a helix form, which explains the origin of the term helictite. The Sr and Ba concentrations measured by laser ablation along helictites can be explained by cation incorporation during calcite precipitation close to equilibrium. Dilution effects caused by seasonality control the elemental distribution in the helictite, which result in a positive correlation between Sr and Ba. Variability of Mg is unrelated with Sr and Ba, and is probably due to the incongruent dissolution of Mg–calcite from the host rock.


      PubDate: 2014-06-14T19:10:38Z
       
  • Natural salinity sources in the groundwaters of Jordan—Importance of
           sustainable aquifer management
    • Abstract: Publication date: Available online 17 May 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Elias Salameh , Marwan Alraggad , Arwa Tarawneh
      In recent years, voices in Jordan became lauder to exploit the fresh to brackish deep groundwater overlain by fresh groundwater bodies. In this article the implications of such a policy on the existing fresh water bodies are worked out through studying the sources of salinity in the different aquifer systems and the potentials of salinity mobilization by artificial changes in the hydrodynamic regimes. It is concluded that extracting the groundwater of deep aquifers overlain by fresh water bodies, whether the deep groundwater is fresh to brackish, brackish or salty, is equivalent to extracting groundwater from the overlying fresh groundwater bodies because of the hydraulic connections of the deep and the shallow aquifers’ groundwaters. The consequences are even more complicated and severe because exploiting the deep groundwater containing brackish or salty water will lead to refilling by fresh groundwater leaking from the overlying aquifers. The leaking water becomes salinized as soon as it enters the pore spaces of the emptied deep aquifer matrix and by mixing with the deep aquifer brackish or saline groundwater. Therefore, the move to exploit the deep groundwater is misleading and damaging the aquifers and is unjust to future generation's rights in the natural wealth of Jordan or any other country with similar aquifers’ set-up. In addition, desalination produces brines with high salinity which cannot easily be discharged in the highlands of Jordan (with only very limited access to the open sea) because they will on the long term percolate down into fresh water aquifers.


      PubDate: 2014-06-14T19:10:38Z
       
  • Distribution of 238U, 232Th and 40K in plutonic rocks of Greece
    • Abstract: Publication date: Available online 3 June 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Argyrios Papadopoulos , Georgios Christofides , Antonios Koroneos , Constantinos Papastefanou , Stylianos Stoulos
      One hundred and twenty one samples from every major plutonic body (mainly granitic) of Greece have been analyzed by γ-ray spectrometry to determine the specific activities of 238U, 232Th and 40K (Bq/kg). The range of the activity concentrations of these radionuclides was 2.3–266.4, 1.8–375.5 and 55.0–1632.0Bq/kg and their average values were 79.2, 85.3 and 881.4Bq/kg respectively. Any possible connection between the specific activities of 238U, 232Th and 40K and some characteristics of the studied samples (age, rock-type, colour, grain-size, occurrence and chemical composition) is investigated. Samples of particular colour, rock-type, occurrence and chemical composition have been identified for their distinctive levels of natural radioactivity, while age and grain-size do not affect the concentrations of 238U, 232Th and 40K. The range of the Th/U ratio was 0.7–12.69. This great variation in the Th/U ratios, especially when it is found among the samples of the same pluton, is also discussed and explained by alteration and tectonic–metamorphic processes.


      PubDate: 2014-06-14T19:10:38Z
       
  • Meteoritic zircon – Occurrence and chemical characteristics
    • Abstract: Publication date: Available online 8 June 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Julia Roszjar , Martin J. Whitehouse , Addi Bischoff
      In common with the remarkable variation in the bulk rock Zr content of distinct meteorite groups, ranging from <1ppm to >800ppm, the occurrence and abundance of accessory zircon is also highly diverse and limited to certain meteorite classes. A detailed literature study on the occurrence of meteoritic zircon, along with other Zr-bearing phases reveals that lunar rocks, eucrites and mesosiderites are the prime sources of meteoritic zircon. Rare zircon grains occur in chondrites, silicate-bearing iron meteorites and Martian meteorites, with grain sizes of >5μm allowing chemical and chronological studies at high spatial resolution using secondary ion mass spectrometry (SIMS) technique. Grain sizes, crystal habits, structural and chemical characteristics of zircon grains derived from various meteorite types, including their REE abundances, minor element concentrations, and Zr/Hf values is diverse. Superchondritic Zr/Hf values (47±8; s.d. with n =97), i.e., typical for zircon in eucrites and mesosiderites, indicate crystallization from a fractionated, incompatible-element-rich (residual) melt. Differences in REE abundances, occurrence or absence of Ce- and Eu-anomalies, and overall REE patterns that are often fractionated with a depletion in LREE, might be primarily controlled by variable formation conditions of individual grains and/or differences in the residual melt compositions on a small, local scale within single samples. Subsequent fractionation/modification of the chemical fingerprint of meteoritic zircon can involve high-temperature annealing processes during thermal metamorphic reactions and/or impact events along with mixing of lithic fragments since many samples are breccias.


      PubDate: 2014-06-14T19:10:38Z
       
  • New insights on mobility and bioavailability of heavy metals in soils of
           the Padanian alluvial plain (Ferrara Province, northern Italy)
    • Abstract: Publication date: Available online 7 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Dario Di Giuseppe , Livia Vittori Antisari , Chiara Ferronato , Gianluca Bianchini
      Heavy metals having both natural and anthropogenic origin are common contaminants in soils and sediments, and can be transferred and bioaccumulated at all levels of the food chain, posing serious environmental concern to the local population. In this paper, agricultural soils from the Province of Ferrara (easternmost part of the Padanian Plain, northern Italy) were investigated to assess the levels of potentially toxic metals in relation to their phytoavailability. Agricultural soils have been sampled in order to identify the origin, mobility and bioavailability of heavy metals, collecting superficial and deeper (depths of 20–30 and 100–120cm, respectively) horizons. The “total” XRF analyses properly elaborated with a statistical approach reveal that soils evolved from two distinct types of alluvial sediments, in turn related to the Po and Reno rivers; the former type is distinctively enriched in heavy metals (particularly Cr and Ni), reflecting the presence of femic and ultrafemic rocks in the hydrological basin of River Po. The absence of Top Enrichment Factors for Ni, Co, Cr, V, and Pb suggests that the content of these elements is natural and unaffected by contamination, whereas superficial enrichments of Cu (and Zn) is ascribed to anthropogenic inputs related to agricultural activities. Multiple extraction tests using variously aggressive reactants (aqua regia, DTPA, EDTA, NH4NO3, and H2O) analyzed by ICP gave insights on the specific mobility of the distinct elements, which decreases in the following order: Pb>Cu>Cd>Co>>Ni>Cr. Taking into consideration the elements that are inducing the main concerns, Cr appears scarcely mobile, whereas Ni could be more phytoavailable and has to be monitored in the local agricultural products. Cd although scarcely abundant has to be monitored for its mobility and toxicity, whereas Cu although abundant and extremely mobile doesn’t induce concerns as it is not hazardous for the living receptors.


      PubDate: 2014-04-29T12:55:46Z
       
  • Evolution of groundwater chemistry in and around Vaniyambadi Industrial
           Area: Differentiating the natural and anthropogenic sources of
           contamination
    • Abstract: Publication date: Available online 11 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): P.J. Sajil Kumar
      Groundwaters in the crystalline aquifers are the major source of drinking water in Vaniyambadi area of Vellore district. Geochemical methods in collaboration with statistical methods were applied in this industrial area to understand the natural and anthropogenic influences on groundwater quality. To accomplish this objective, groundwater samples were collected and analyzed for physicochemical parameters and the results showed a dominance in the order of Na+ >Mg2+ >Ca2+ >K+ and HCO3 − >Cl− >SO4 2− >NO3 − for anions and cations, respectively. In contrast to this anion dominance were changed to Cl− >HCO3 − >SO4 2− >NO3 − in samples collected near the tannery industries. Groundwater quality evaluation using TDS and TH suggested that 57% of the total samples are hard-brackish type, indicating its unsuitability for drinking purpose. Generally the water type is Na+ Cl− to Ca2+ Mg2+ HCO3 − type with an intermediate Ca2+ Mg2+ Cl−, suggesting the mixing of fresh groundwater with tannery effluent and cation exchange. Factor analysis and bivariate plots of major ions suggests that both natural and anthropogenic inputs are equally influencing the groundwater quality. Further investigations proved that silicate weathering is the dominant geogenic source of groundwater solute content, whereas tannery effluent is the anthropogenic source. Saline water mixing index (SWMI) and Cl− vs NO3 − bivariate plot were employed to differentiate the tannery contamination from the other anthropogenic inputs such as agricultural fertilizers, municipal sewages, etc. This analysis shows that samples 2, 4, 8 and 9 (located within the tannery cluster) have a SWMI value greater than 1, representing the groundwater–tannery effluent mixing. This study infers that groundwater in the Vaniyambadi area is under serious threat from both natural and anthropogenic contamination. However, the controlling discharge of untreated tannery effluents must be regulated to reduce the further deterioration of this vital resource in this part of the country.


      PubDate: 2014-04-29T12:55:46Z
       
  • Mineralogy and speciation of Zn and As in Fe-oxide-clay aggregates in the
           mining waste at the MVT Zn–Pb deposits near Olkusz, Poland
    • Abstract: Publication date: Available online 18 April 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Irena Jerzykowska , Juraj Majzlan , Marek Michalik , Jörg Göttlicher , Ralph Steininger , Artur Błachowski , Krzysztof Ruebenbauer
      Oxidation zones of ore deposits offer valuable insights into the long-term fate of many metals and metalloids. In this work, we have studied a paleo-acid rock drainage (ARD) system – the oxidation zone of Mississippi-valley type Zn–Pb deposits near Olkusz in southern Poland. The ARD systems exhausted their acid-generating capacity and have come almost to the conclusion of the mineral and geochemical transformations. Primary pyrite, marcasite, galena and sphalerite have been decomposed but the acidity was neutralized by the abundant carbonate host rocks. Zinc is stored in smithsonite, hemimorphite, and Zn-rich sheet aluminosilicates. Some of these minerals formed simultaneously with the oxidation zone but some precipitated in the soils in situ, thus documenting the mobility of Zn, Al, and Si in the soils. Iron oxides are represented mostly by goethite, either well-crystalline or nanocrystalline, as determined by a combination of powder X-ray diffraction, micro-X-ray diffraction, and Mössbauer spectroscopy. Iron oxides bind a substantial amount of arsenic, to a lesser extent also zinc, lead, and cadmium, as shown by electron microprobe analyses and sequential extractions. The X-ray absorption spectroscopy data of the local environment of arsenic in goethite suggest the existence of bidentate mononuclear complex, in addition to the more common bidentate binuclear complex. These results suggest that arsenic is incorporated in the crystal structure of goethite, in addition to adsorbed to the surface of the particles or occluded in the voids and pores. Zinc is bound in goethite as a mixture of tetrahedrally and octahedrally coordinated cations. This study shows that the mature system binds the metals from the primary sulfides relatively strongly. Yet, some release of the metals was observed in this study, either in the laboratory (by sequential extractions) and in nature (e.g., neoformed Zn phyllosilicates). The physical conditions in the oxidation zone and on the surface are largely similar but the metals, to a certain extent, are still mobile in the soils. We may speculate that their mobility near the surface, in the mining waste, may be enhanced by a higher water/rock ratio than in the oxidation zone. This result implies that although the studied material is relatively benign, it still has a potential to cause local environmental problems.


      PubDate: 2014-04-29T12:55:46Z
       
  • Long-lived magmatic systems and implications on the recognition of
           granite–pegmatite genetic relations: Characterization of the Pavia
           granitic pegmatites (Ossa-Morena Zone, Portugal)
    • Abstract: Publication date: Available online 11 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Selma M. Lima , Ana M.R. Neiva , João M.F. Ramos , Andrés Cuesta
      It is generally accepted that pegmatites are derived from large masses of granite but, even in areas where complete mineralogical, chemical and isotopic datasets are available, the relation between pegmatites and host granitic rocks or nearby plutons is usually not simple to address. The Pavia pluton, located in the Ossa-Morena Zone (Iberian Massif), is a multiphase intrusive body constructed over ∼11m.y. by the amalgamation of several batches of magma. At the first glance, pegmatites seem to constitute a very homogeneous pegmatite field. They are mainly “intragranitic” thin tabular dikes, unzoned, layered, or with simple internal structure and are composed by the ordinary minerals that constitute the different classes of igneous rocks. They also present identical whole rock major and trace elements geochemistry and isotopic signature [(87Sr/86Sr) i =0.70434–0.70581, ɛNd t =−1.3 to −3.7 and δ 18O=8.2–9.6‰] but, based on previously published geochronological data, three generations of pegmatites were identified. Two of these are coeval with the emplacement of the host granites (s.l.) at 328Ma and ca. 324Ma. The other is related to a later magmatic event at 319–317Ma. A similar and rather juvenile source is suggested for host granites (s.l.) and pegmatites but a simple and continuous process of intra-chamber magmatic differentiation is not supported by our data. It is suggested that pegmatites derived from slightly evolved batches of magma that interacted with fresh, newly emplaced, batches (from the same or from a similar source) with limited interaction with the crust. Therefore, the Pavia pegmatites do not represent the final products of magmatism at this level of the crust but slightly differentiated products of different batches of magma. This study demonstrates how long-lived magmatic systems can potentially affect the recognition of granite–pegmatite genetic relationships.


      PubDate: 2014-04-29T12:55:46Z
       
  • Homogeneity testing of microanalytical reference materials by electron
           probe microanalysis (EPMA)
    • Abstract: Publication date: Available online 19 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Dennis Harries
      Homogeneity testing of candidate reference materials requires distinguishing the effects of measurement uncertainty of the analytical method from true compositional variations within the material. Many in situ microanalytical techniques do not allow classical ANOVA homogeneity testing due to the infeasibility of truly replicated analyses on the same analysis volume. This also applies to the analysis of beam-sensitive and light element-bearing materials by electron probe microanalysis (EPMA). This reality has led me to reconsider the homogeneity index approach used in the testing of microanalytical reference materials by EPMA. Based on statistical considerations, I show that the homogeneity index is suitable for statistical significance testing using F and chi-squared statistics and allows estimating the contribution of compositional heterogeneity to the total uncertainty budget of the referenced values. However, there are problems of bias and masking of small compositional variations by measurement uncertainty. This contribution shows the strong impact of the total number of measurements on the resolution of a microanalytical homogeneity study and discusses how to quantify the relative contribution of heterogeneity to the total uncertainty budget. I present an example of EPMA to illustrate this approach and show some pitfalls and limitations in its application.


      PubDate: 2014-04-29T12:55:46Z
       
  • Planetary and pre-solar noble gases in meteorites
    • Abstract: Publication date: Available online 19 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Ulrich Ott
      Noble gases are not rare in the Universe, but they are rare in rocks. As a consequence, it has been possible to identify in detailed analyses a variety of components whose existence is barely visible in other elements: radiogenic and cosmogenic gases produced in situ, as well as a variety of “trapped” components – both of solar (solar wind) origin and the “planetary” noble gases. The latter are most abundant in the most primitive chondritic meteorites and are distinct in elemental and isotopic abundance patterns from planetary noble gases sensu strictu, e.g., those in the atmospheres of Earth and Mars, having in common only the strong relative depletion of light relative to heavy elements when compared to the solar abundance pattern. In themselves, the “planetary” noble gases in meteorites constitute again a complex mixture of components including such hosted by pre-solar stardust grains. The pre-solar components bear witness of the processes of nucleosynthesis in stars. In particular, krypton and xenon isotopes in pre-solar silicon carbide and graphite grains keep a record of physical conditions of the slow-neutron capture process (s-process) in asymptotic giant branch (AGB) stars. The more abundant Kr and Xe in the nanodiamonds, on the other hand, show a more enigmatic pattern, which, however, may be related to variants of the other two processes of heavy element nucleosynthesis, the rapid neutron capture process (r-process) and the p-process producing the proton-rich isotopes. “Q-type” noble gases of probably “local” origin dominate the inventory of the heavy noble gases (Ar, Kr, Xe). They are hosted by “phase Q”, a still ill-characterized carbonaceous phase that is concentrated in the acid-insoluble residue left after digestion of the main meteorite minerals in HF and HCl acids. While negligible in planetary-gas-rich primitive meteorites, the fraction carried by “solubles” becomes more important in chondrites of higher petrologic type. While apparently isotopically similar to Q gas, the elemental abundances are somewhat less fractionated relative to the solar pattern, and they deserve further study. Similar “planetary” gases occur in high abundance in the ureilite achondrites, while small amounts of Q-type noble gases may be present in some other achondrites. A “subsolar” component, possibly a mixture of Q and solar noble gases, is found in enstatite chondrites. While no definite mechanism has been identified for the introduction of the planetary noble gases into their meteoritic host phases, there are strong indications that ion implantation has played a major role. The planetary noble gases are concentrated in the meteorite matrix. Ca-Al-rich inclusions (CAIs) are largely planetary-gas-free, however, some trapped gases have been found in chondrules. Micrometeorites (MMs) and interplanetary dust particles (IDPs) often contain abundant solar wind He and Ne, but they are challenging objects for the analysis of the heavier noble gases that are characteristic for the planetary component. The few existing data for Xe point to a Q-like isotopic composition. Isotopically Q-Kr and Q-Xe show a mass dependent fractionation relative to solar wind, with small radiogenic/nuclear additions. They may be closer to “bulk solar” Kr and Xe than Kr and Xe in the solar wind, but for a firm conclusion it is necessary to gain a better understanding of mass fractionation during solar wind acceleration.


      PubDate: 2014-04-29T12:55:46Z
       
  • Physical-chemical and electrochemical characterization of Fe-exchanged
           natural zeolite applied for obtaining of hydrogen peroxide amperometric
           sensors
    • Abstract: Publication date: Available online 20 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Andrada Maicaneanu , Codruta Varodi , Horea Bedelean , Delia Gligor
      This work demonstrates that a Fe-exchanged zeolitic volcanic tuff from Cepari (Fe/CV) (Bistrita-Nasaud County, Romania) is suitable for the amperometric detection of H2O2, using new modified carbon paste electrodes based on this material (Fe/CV-CPEs). The physical-chemical characterization of natural (CV) and modified (Fe/CV) forms was realized using chemical analysis, optical microscopy, scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The resulting electrodes (Fe/CV-CPEs) were investigated using cyclic voltammetry and chronoamperometry measurements. The new electrodes showed good electrocatalytic activity toward H2O2 reduction. The calibration curve for H2O2 determination was linear up to 0.1mM, with a detection limit (signal to noise ratio of 3) of 20μM.


      PubDate: 2014-04-29T12:55:46Z
       
  • Element contents in shoots of sunflower (Helianthus annuus): Prediction
           versus measuring
    • Abstract: Publication date: Available online 22 March 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): A. Kötschau , G. Büchel , J.W. Einax , D. Mirgorodsky , R. Meißner , W. von Tümpling , D. Merten
      Sunflower (Helianthus annuus) is cultivated as food and feed crop as well as for bioenergy production. It is also investigated towards its ability to remove contaminants from soil and accumulate them in the shoots (phytoextraction). So the reliable prediction of element contents in shoots based on soil contents would be advantageous to easily decide whether plants grown on a certain area could be either used as food and feed or for phytoremediation in combination with bioenergy production. However, it is desirable to predict element contents in plants based on only a few numbers of predictors. This would mean on the one hand a reduced effort in time and costs for analysis and on the other hand existing data on soil quality could be than used for estimations of the element uptake of plants on larger scales. Samples of sunflowers were used, that were grown in plots situated at two different sites in Germany and treated with different amendments (NPK-fertilizer, Streptomyces+Mycorrhiza, Rendzina). One site (heavy metal polluted) was the test field “Gessenwiese”, which is situated on the area of the former uranium leaching heap “Gessenhalde”. The other site (non-contaminated) was the lysimeter station Falkenberg. Shoot contents of Ca, Cd, Co, Cu, K, Ni, Pb, and Zn were correctly predicted by the mobile soil fraction extracted with 1M NH4NO3 solution (simple regression), whereas for Mg, S, and U the specifically adsorbed soil fraction (extraction with 1M NH4OAc solution) needs to be added as predictor (PLS regression). Mn was the only element in the data set for which simple regression based on total soil contents (digestion with HF, HClO4, and HNO3) had to be used be used for correct prediction in the studied data set.


      PubDate: 2014-04-29T12:55:46Z
       
  • Uranium distribution in the sediment of the Mianyuan River near a
           phosphate mining region in China and the related uranium speciation in
           water
    • Abstract: Publication date: Available online 1 April 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Xinyu Wang , Shijun Ni , Zeming Shi
      To clarify the mechanisms of uranium distribution in river sediment and its speciation in river water near a phosphate mining region, the sediment and river water in the Mianyuan River in China were investigated. Using linear correlation analysis, it was determined that uranium distribution in upstream sediment is mainly controlled by the adsorption of organic compounds ( R TOC-U 2 = 0.848 ), whereas distribution is controlled by physical deposition of albite ( R Na-U 2 = 0.773 ) in downstream sediment. In addition, it was determined that Se and As had strong and positive linear correlations with uranium in sediment, regardless of whether it was upstream or downstream sediment. This type of relationship was also found in phosphate ores, which suggests that the ore is the common source of U, Se and As in the sediment. The results of speciation-solubility modelling suggest that no precipitation of uranium minerals occurred in river water and the dominant uranium species in river water included: UO2(HPO4)2 2−, Ca2UO2(CO3)3 and UO2(CO3)3 4−. In addition, our modelling indicated the relative species distribution was mainly affected by the pH and the total phosphate concentration.


      PubDate: 2014-04-29T12:55:46Z
       
  • Hydrogeochemical characterization of major factors affecting the quality
           of groundwater in southern Iran, Janah Plain
    • Abstract: Publication date: Available online 28 April 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Mehdi Zarei , Fuzieh Sedehi , Ezzat Raeisi
      The Janah alluvial aquifer is located in southern Iran with an arid climate. The type of groundwater in this aquifer is dominantly of sodium chloride and total dissolved solid of groundwater samples range from 1.63 to 335g/L which confirms that groundwater quality has been severely degraded by salinization. Hydrogeochemical and isotopic investigations were conducted to identify the source of salinity. Total dissolved solids and major ion concentrations were measured at 51 selected sampling sites including springs, wells and surface waters. In addition stable isotopic composition (oxygen-18 and deuterium) was measured in 6 sampling points. The study indicates that the sources of salinity of the Janah aquifer include dissolution of salt diapir and evaporite rocks, a geothermal spring and intrusion of the river water which function individually or together in different parts of the aquifer. Based on the hydrogeochemical and geological studies conceptual flow models were prepared for different parts of the aquifer which illustrate how each source of salinity deteriorates the quality of the alluvial aquifer. We proposed few remediation methods including construction of cemented channel and sealed basins to improve groundwater quality. These methods would prevent infiltration of low quality water into the alluvial aquifer.


      PubDate: 2014-04-29T12:55:46Z
       
  • Brachinite meteorites: Partial melt residues from an FeO-rich asteroid
    • Abstract: Publication date: Available online 19 April 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Klaus Keil
      Brachinites are ultramafic, dunitic to wherlitic, unbrecciated and essentially unshocked rocks that are low in SiO2 (∼36–39wt.%), high in MgO (∼27–30wt.%) and notably high in FeO (∼26–37wt.%), and low in Al2O3 (∼0.2–2.5wt.%) and combined alkalis Na2O and K2O (∼0–0.7wt.%). They consist mostly of olivine (∼71–96vol.%; ∼Fo64–73), major clinopyroxene (minor to ∼15vol.%; ∼En40–63Wo36–48), with variable small amounts of plagioclase (0 to ∼10vol.%; ∼An15–33), and minor to trace amounts of orthopyroxene (none to ∼20vol.%; En69–73Wo2–4), Fe-sulfides (trace to ∼7vol.%), chromite (none to ∼5vol.%), phosphates (none to ∼3vol.%) and metallic Fe,Ni (trace to ∼2vol.%). Minerals tend to be homogeneous, and textures are medium to coarse-grained (∼0.1–1.5mm), with olivine commonly displaying triple junctions. Brachina has near-chondritic lithophile element abundances, whereas other brachinites show variable depletions in Al, Ca, Rb, K, Na, and LREE. Siderophile element abundance patterns vary and range from ∼0.01 to ∼0.9 CI. Oxygen isotope composition (Δ17O) ranges from ∼−0.09 to −0.39‰, with the mean=−0.23±0.14‰. Brachinites are ancient rocks, as was recognized early by the detection, in some brachinites, of excess 129Xe from the decay of short-lived 129I (half-life 17Ma) and of fission tracks from the decay of 244Pu (half-life 82Ma) in phosphate, high-Ca clinopyroxene and olivine. The first precise crystallization age was determined for Brachina using 53Mn–53Cr systematics, relative to the Pb–Pb age of the angrite LEW 86010, and yielded an age of 4563.7±0.9Ma. Thus, Brachina is at most ∼4Ma younger that the CAIs whose age is 4567.2±0.6Ma. There is no consensus on the origin of brachinites, but they most likely are primitive achondrites, i.e., ultra-mafic residues from various low degrees of partial melting. Partial melting experiments suggest that they possibly formed from a parent lithology chemically similar but not identical to the Rumuruti (R) chondrites, although the different oxygen isotopic compositions of the R chondrites and the brachinites put a serious constraint on this hypothesis. The apparent lack of abundant rocks representing the partial melts suggests that brachinites may have formed on a parent body <∼100km in radius, where early partial melts were removed from the parent body by explosive pyroclastic volcanism. Graves Nunataks 06128 and 06129 are felsic, andesitic basalts which have properties that suggest a relationship to brachinites and thus, may be samples of the elusive partial melts.


      PubDate: 2014-04-29T12:55:46Z
       
 
 
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