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  Subjects -> EARTH SCIENCES (Total: 586 journals)
    - EARTH SCIENCES (433 journals)
    - GEOLOGY (65 journals)
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EARTH SCIENCES (433 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: 12)
Advances In Physics     Hybrid Journal   (Followers: 6)
Aeolian Research     Hybrid Journal   (Followers: 1)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 2)
AMBIO     Hybrid Journal   (Followers: 13)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 2)
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: 14)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene Review     Hybrid Journal  
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 6)
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: 8)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 20)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 13)
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: 3)
Atmospheric and Climate Sciences     Open Access   (Followers: 14)
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: 8)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 9)
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: 15)
Bulletin of Volcanology     Hybrid Journal   (Followers: 11)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 17)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
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: 9)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 10)
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: 7)
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: 135)
Earth Interactions     Full-text available via subscription   (Followers: 8)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 1)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 11)
Earth System Dynamics     Open Access   (Followers: 4)
Earth System Dynamics Discussions     Open Access   (Followers: 3)
Earth's Future     Open Access   (Followers: 1)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Spectra     Full-text available via subscription   (Followers: 11)
Ecohydrology     Hybrid Journal   (Followers: 11)
Ecological Questions     Open Access   (Followers: 6)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 9)
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  
Erwerbs-Obstbau     Hybrid Journal  

        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  [2563 journals]   [SJR: 0.612]   [H-I: 23]
  • Geochemistry of an ENE–WSW to NE–SW trending ∼2.37Ga
           mafic dyke swarm of the eastern Dharwar craton, India: Does it represent a
           single magmatic event'
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Rajesh K. Srivastava , M. Jayananda , Gulab C. Gautam , V. Gireesh , Amiya K. Samal
      A vast tract of ENE–WSW to NE–SW trending mafic dyke swarm transects Archaean basement rocks within the eastern Dharwar craton. Petrographic data reveal their dolerite/olivine dolerite or gabbro/olivine gabbro composition. Geochemical characteristics, particularly HFSEs, indicate that not all these dykes are co-genetic but are probably derived from more than one magma batch and different crystallization trends. In most samples the LaN/LuN ratio is at ∼2, whereas others have a LaN/LuN ratio >2 and show higher concentrations of high-field strength elements (HFSEs) than the former group. As a consequence, we assume that the ENE–WSW to NE–SE trending mafic dykes of the eastern Dharwar craton do not represent one single magmatic event but were emplaced in two different episodes; one of them dated at about 2.37Ga and another probably at about 1.89Ga. Trace element modelling also supports this inferen older mafic dykes are derived from a melt generated through ∼25% melting of a depleted mantle, whereas the younger set of dykes shows its derivation through a lower degree of melting (∼15%) of a comparatively enriched mantle source.


      PubDate: 2014-06-14T19:10:38Z
       
  • Fossil fuel compounds from fly dust in recent organic matter of southern
           Poland peats
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Monika J. Fabiańska , Artur Szymczyk , Magdalena Chłapik
      Several samples of peat from 6 bogs located in southern Poland were investigated for occurrence and distribution types of biomarkers present in their extractable organic matter fraction. It was found that there are inputs from two different sources of organic compounds differing in their characteristics and origin: (1) recent immature peat organic matter deposited in situ which is the source of all polar functionalized compounds, most of n-alkanes, and acyclic isoprenoids, and (2) mature fossil fuels, most probably bituminous coals from the Upper Silesia Coal Basin of vitrinite reflectance equivalent values of 0.9–1.1%. The latter compounds were most probably transported with fly ash to bogs from nearby settlements utilizing such fuel in domestic ovens. This group includes pentacyclic triterpenoids (hopanes and moretanes), minor amounts of n-alkanes, and numerous alkyl naphthalenes and alkyl phenanthrenes. All these compounds show distributions and values of geochemical ratios characteristic for mature organic matter confirming there ex situ origin.


      PubDate: 2014-06-14T19:10:38Z
       
  • 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
       
  • Geochronology and geochemistry of Middle Devonian mafic dykes in the East
           Kunlun orogenic belt, Northern Tibet Plateau: Implications for the
           transition from Prototethys to Paleotethys orogeny
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Fuhao Xiong , Changqian Ma , Hong’an Jiang , Bin Liu , Jian Huang
      The tectonic transition from Prototethys to Paleotethys orogeny in the East Kunlun orogenic belt is not completely clear, and is a major unresolved geologic issue in Northern Tibet Plateau. Here, we present zircon geochronology, whole-rock elemental and zircon Hf isotopic geochemistry for newly discovered mafic dykes in the East Kunlun orogenic belt, to provide constraints on this issue. The studied mafic dykes are hornblende gabbros, consisting of hornblende (60–65vol.%), plagioclase (15–25vol.%) and augite and biotite (0–5vol.%). LA–ICP–MS zircon U–Pb dating shows that these mafic dykes were emplaced at about 393Ma. All the mafic dykes are characterized by high contents of CaO (8.82–11.48wt.%), MgO (9.07–11.39wt.%), V (275–336ppm), Cr (370–467ppm) and Ni (78.3–120ppm), with high Mg# (63–67), flat CI-normalized REE distribution and depleted ɛHf(t) values (2.03–5.35), showing tholeiitic affinities and geochemical characteristics similar to those of mid-ocean ridge basalts. They were derived from low degree (about 5–15%) partial melting of a fertile spinel lherzolite source, which have been metasomatized by fluids introduced to the mantle by former subducted slab. The geologic–petrologic evidence suggests that the mafic dykes were emplaced in a shift tectonic setting related to continental rifting, which was caused by the extensional collapse related to the lithospheric thinning after the Prototethys orogeny. The delamination-induced thermal disturbance and extensional decompression triggered partial melting of the mantle and the emplacement of the mafic dykes. Combined with previous work, we propose that the Middle Devonian mafic dykes may be the early magmatic response to the transition from Prototethys to Paleotethys marking the opening of the Paleotethys in the East Kunlun orogenic belt.


      PubDate: 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
       
  • Note on the isotopic geochemistry of fossil-lacustrine tufas in carbonate
           plateau—A study from Dungul region (SW Egypt)
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Kamaleldin M. Hassan
      Lithological, chemical, and stable isotope data are used to characterize lacustrine tufas dating back to pre-late Miocene and later unknown times, capping different surfaces of a Tertiary carbonate (Sinn el-Kedab) plateau in Dungul region in the currently hyperarid south-western Egypt. These deposits are composed mostly of calcium carbonate, some magnesium carbonate and clastic particles plus minor amounts of organic matter. They have a wide range of (Mg/Ca)molar ratios, from 0.03 to 0.3. The bulk-tufa carbonate has characteristic isotope compositions: (δ 13Cmean =−2.49±0.99‰; δ 18Omean =−9.43±1.40‰). The δ 13C values are consistent with a small input from C4 vegetation or thinner soils in the recharge area of the tufa-depositing systems. The δ 18O values are typical of fresh water carbonates. Covariation between δ 13C and δ 18O values probably is a reflection of climatic conditions such as aridity. The tufas studied are isotopically similar to the underlying diagenetic marine chalks, marls and limestones (δ 13Cmean =−2.06±0.84‰; δ 18Omean =−10.06±1.39‰). The similarity has been attributed to common meteoric water signatures. This raises large uncertainties in using tufas (Mg/Ca)molar, δ 13C and δ 18O records as proxies of paleoclimatic change and suggests that intrinsic compositional differences in material sources within the plateau may mask climatic changes in the records.


      PubDate: 2014-06-14T19:10:38Z
       
  • Geochemistry, provenance and tectonic setting of the Late
           Cambrian–Early Ordovician Seydişehir Formation in the
           Çaltepe and Fele areas, SE Turkey
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Mehmet Muzaffer Karadağ
      The major, trace and rare earth element (REE) contents of metapelite (MPL), metapsammite (MPS) and metamarl (MM) samples from the Cambro-Ordovician Seydişehir Formation were analyzed to investigate their provenance and tectonic setting. The MPS, MPL, and MM samples have variable SiO2 concentrations, with average values of 72.36, 55.54, and 20.95wt%, moderate SiO2/Al2O3 ratios (means of 6.88, 3.23, and 3.80), moderate to high Fe2O3 +MgO contents (means of 5.14, 9.55, 3.56wt%), and high K2O/Na2O ratios (means of 3.26, 3.64, 2.90), respectively. On average, the chemical index of alteration (CIA) values of the MPS and the MPL are 65.87 and 71.96, respectively, while the chemical index of weathering (CIW) values are 74.54 and 85.09, respectively. These data record an intermediate to high degree of alteration (weathering) of plagioclase to illite/kaolinite in the samples’ provenance. The chondrite-normalized REE patterns of all the sample groups are similar and are characterized by subparallel light rare earth elements (LREE)-enriched, relatively flat heavy rare earth elements (HREE) patterns with pronounced Eu anomalies (mean of 0.69) and moderate fractionation [average (La/Yb) N =8.7]. Plots of sediments in ternary diagrams of La, Th, Sc and elemental ratios (La/Sc, Th/Sc, Cr/Th, Eu/Eu*, La/Lu, Co/Th, La/Sc and Sc/Th), which are critical for determining provenance, and REE patterns indicate that the metaclastic units of the Seydişehir Formation were derived dominantly from felsic to intermediate magmatic rocks and not from a mafic source. The La–Sc–Th and Th–Sc–Zr/10 ternary diagrams of the Seydişehir Formation are typical of continental island arc/active continental margin tectonic settings. The geologic location and geochemistry of the Seydişehir Formation suggest that it was deposited in an Andean-type retroarc foreland basin during the Late Cambrian–Early Ordovician period. The Neoproterozoic intermediate to felsic magmatic rocks and metaclastic sediments with felsic origins of the Sandıklı–Afyon Basement Complex (SBC) and their equivalent units, which are thought to be overlain by the younger units in the study area, may be the dominant source rocks for the Seydişehir Formation.


      PubDate: 2014-06-14T19:10:38Z
       
  • Geochemistry and origin of the Cretaceous sedimentary kaolin deposits, Red
           Sea, Egypt
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Hassan M. Baioumy
      This work reports, for the first time, the mineralogical and geochemical characteristics of the Cretaceous sedimentary kaolin deposits in the Red Sea area, Egypt and sheds the light on their source. Mineralogical and geochemical analyses of both bulk deposits and the sand and clay fractions of these deposits indicated that they are composed of kaolinite (average of 75wt.%) and quartz (average of 22wt.%). Traces of anatase (average of 1wt.%) were identified in all kaolin samples, while traces of halite (average of 2wt.%) and hematite (average of 1wt.%) were reported in the majority of the analyzed samples. The clay fractions show relatively high contents of TiO2 (average of 2.1%), Ni (average of 103ppm), Nb (average of 98ppm), Y (average of 67ppm), and Zr (average of 630ppm). Sum of the rare earth elements (ΣREE) in the clay fractions varies between 193 and 352ppm. Chondrite-normalized REE patterns show enrichment of the light REE relative to the heavy REE ((La/Yb) N =9) and negative Eu anomaly (Eu*/Eu=0.67). Major, trace, and rare earth elements geochemistry of the clay fractions from the studied kaolin deposits suggested that these deposits were derived from a mixture of more than source rocks probably a mixture of mafic, granitic, and alkaline rocks. The contribution of granitic rocks was proposed based on the REE pattern and negative Eu anomaly as well as the high Zr and Y contents, while the contribution of mafic rocks to the source was suggested based on the relatively high TiO2 and Ni contents. The abnormally high Nb contents in the clay fractions of the Red Sea kaolin deposits indicated a contribution of alkaline rocks to the source of these deposits. Igneous and metamorphic rocks of different composition belonging to the Arabian-Nubian Shield are located very close to the studied deposits. The monomineralic nature of the Red Sea kaolin deposits as kaolinite, abundance of organic matter, and absence of any marine fossils suggested a non-marine depositional environment of these deposits. Occurrence of halite in the studied deposit is probably due to sea breezes since the studied deposits are located close to the Gulf of Suez.


      PubDate: 2014-06-14T19:10:38Z
       
  • Mineralogy and geochemical behaviour during weathering of greenstone belt
           under tropical dry conditions in the extreme North Cameroon (Central
           Africa)
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Jean Pierre Nguetnkam , Fredéric Villiéras , Richard Kamga , Georges Emmanuel Ekodeck , Jacques Yvon
      Mineralogy, major, trace and rare earth elements of a weathering profile developed on tertiary greenstone belt in the extreme North Cameroon are reported. The aim of which was to investigate mineralogical evolution and element mobilization and redistribution during weathering under dry tropical climate. The weathering profile consists of four main horizons: (1) a spheroidal weathering zone constituted by a corestone–shell complex, (2) a C horizon, (3) a Bw horizon and an Ah horizon. The results indicate that nontronite, a Fe-rich smectite, is the exclusive clay mineral formed in the exfoliated shells and the C horizon. It is associated with kaolinite in the upper horizons. The coexistence of these two clay minerals induced a decrease of CEC and pH which becomes neutral. The weathering index (WI) values reveal that weathering becomes more and more intensive from the corestone up to Bw horizon, which is the most weathered horizon in the weathering profile. Mass balance calculations, using Th as immobile element, indicate that Ti is quite mobile and that Al and Fe are relatively enriched at the bottom and strongly leached at the top of the profile. Alkalis and alkaline earth elements are strong leached through out the profile, except Ca which displays similar trend as Al and Fe. The same goes for LILE (Cs, Sr), TTE (Cr, Co, Ni) and HSFE (Y, Nb, Hf). In opposite, REE are depleted at the bottom and enriched in the upper horizons, with more enrichment for LREE than for HREE. It appears that weathering of greenstone belt causes a fractionation of HREE and induces a concentration of LREEs. Ce and Eu anomalies display opposite behaviour.


      PubDate: 2014-06-14T19:10:38Z
       
  • Editorial board members
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2




      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
       
  • Geochemical comparison of waters and stream sediments close to abandoned
           Sb-Au and As-Au mining areas, northern Portugal
    • Abstract: Publication date: June 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 2
      Author(s): Paula C.S. Carvalho , Ana M.R. Neiva , Maria M.V.G. Silva , Eduardo A. Ferreira da Silva
      Waters from abandoned Sb-Au mining areas have higher Sb (up to 2138μgL−1), As (up to 1252μgL−1) and lower Al, Zn, Li, Ni and Co concentrations than those of waters from the As-Au mining area of Banjas, which only contain up to 64μgL−1 As. In general, Sb occurs mainly as SbO3 − and As H2AsO4 −. In general, waters from old Sb-Au mining areas are contaminated in Sb, As, Al, Fe, Cd, Mn, Ni and NO2 −, whereas those from the abandoned As-Au mining area are contaminated in Al, Fe, Mn, Ni, Cd and rarely in NO2 −. Waters from the latter area, immediately downstream of mine dumps are also contaminated in As. In stream sediments from Sb-Au and As-Au mining areas, Sb (up to 5488mgkg−1) and As (up to 235mgkg−1) show a similar behaviour and are mainly associated with the residual fraction. In most stream sediments, the As and Sb are not associated with the oxidizable fraction, while Fe is associated with organic matter, indicating that sulphides (mainly arsenopyrite and pyrite) and sulphosalts containing those metalloids and metal are weathered. Arsenic and Sb are mainly associated with clay minerals (chlorite and mica; vermiculite in stream sediments from old Sb-Au mining areas) and probably also with insoluble Sb phases of stream sediments. In the most contaminated stream sediments, metalloids are also associated with Fe phases (hematite and goethite, and also lepidocrocite in stream sediments from Banjas). Moreover, the most contaminated stream sediments correspond to the most contaminated waters, reflecting the limited capacity of stream sediments to retain metals and metalloids.


      PubDate: 2014-06-14T19:10:38Z
       
  • The Almahata Sitta polymict breccia and the late accretion of asteroid
           2008 TC3
    • Abstract: Publication date: Available online 13 April 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Marian Horstmann , Addi Bischoff
      On October 7, 2008, a small asteroid named 2008 TC3 was detected in space about 19h prior to its impact on Earth. Numerous world-wide observations of the object while still in space allowed a very precise determination of its impact area: the Nubian Desert of northern Sudan, Africa. The asteroid had a pre-atmospheric diameter of ∼4m; its weight is reported with values between ∼8 and 83t, and the bulk density with ∼2–3g/cm3, translating into a bulk porosity in the range of ∼20–50%. Several dedicated field campaigns in the predicted strewn field resulted in the recovery of more than 700 (monolithological) meteorite fragments with a total weight of ∼10.5kg. These meteorites were collectively named “Almahata Sitta”, after the nearby train station 6, and initially classified as an anomalous polymict ureilite. Further work, however, showed that Almahata Sitta is not only a ureilite but a complex polymict breccia containing chemically and texturally highly variable meteorite fragments, including different ureilites, a ureilite-related andesite, metal-sulfide assemblages related to ureilites, and various chondrite classes (enstatite, ordinary, carbonaceous, Rumuruti-like). It was shown that that chondrites and ureilites derive from one parent body, i.e., asteroid 2008 TC3, making this object, in combination with the remotely sensed physical parameters, a loosely aggregated, rubble-pile-like object. Detailed examinations have been conducted and mineral-chemical data for 110 samples have been collected, but more work on the remaining samples is mandatory. Detailed study of Almahata Sitta allows insights into the formation and evolution of ureilites and their parent body. These results support the catastrophic impact disruption of the ureilite parent body and re-accretion of the dispersed ureilitic material into second generation ureilite asteroids. Almahata Sitta shows that different chondritic materials were present in the region of re-accretion and mixed into the newly formed rubble-pile-like asteroid. Asteroid 2008 TC3 was part of a late-formed ureilitic second generation body in the main belt and was liberated ∼20Ma ago, finally moving into Earth-crossing orbits that ultimately led to its impact on Earth. The abundant samples of Almahata Sitta, fragments of Asteroid 2008 TC3, allow study of not only different types of meteorites, but offer the unique opportunity to gain further insights into processes in the asteroid belt of our Solar System such as migration, collision, mixing, and (re-)accretion of asteroidal bodies. Beyond that, this event has the potential to further the understanding of the meteorite–asteroid links, which is a major goal of meteorite science.


      PubDate: 2014-04-29T12:55:46Z
       
  • 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: Available online 20 February 2014
      Source:Chemie der Erde - Geochemistry
      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: 2014-04-29T12:55:46Z
       
  • Geochemistry of Neogene sedimentary rocks from Borneo Basin, East
           Malaysia: Paleo-weathering, provenance and tectonic setting
    • Abstract: Publication date: March 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 1
      Author(s): R. Nagarajan , Priyadarsi D. Roy , M.P. Jonathan , Rufino Lozano , Franz L. Kessler , M.V. Prasanna
      Multi-element geochemistry and mineralogy are used to characterize the chemical composition, degree of paleo-weathering, provenance and tectonic settings of the Neogene sedimentary rocks of Borneo Basin of east Malaysia. Sedimentary rocks are classified as extremely weathered sandstones (i.e. wacke, arkose, litharenite, Fe-sandstone and quartz arenite). Wacke, arkose, litharenite and Fe-sandstone are characterized by post-depositional K-metasomatism and zircon enrichment through sediment recycling. Geochemical characteristics suggest a mixed-nature provenance for the sandstones and the variable tectonic settings possibly mirror the complexity of the basin. Enriched Cr in quartz arenite and Fe-sandstone are related to the contribution from ophiolite or fractionation of Cr-bearing minerals.


      PubDate: 2014-04-29T12:55:46Z
       
  • 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: Available online 26 February 2014
      Source:Chemie der Erde - Geochemistry
      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: 2014-04-29T12:55:46Z
       
  • Permian volcanic rocks from the Apuseni Mountains (Romania): Geochemistry
           and tectonic constraints
    • Abstract: Publication date: March 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 1
      Author(s): Ionel Nicolae , Ioan Seghedi , Iuliu Boboş , Maria do Rosário Azevedo , Sara Ribeiro , Mihai Tatu
      An Early Permian volcanic assemblage is well exposed in the central-western part of the Apuseni Mountains (Romania). The rocks are represented by rhyolites, basalts and subordinate andesites suggesting a bimodal volcanic activity that is intimately associated with a post-orogenic (Variscan) syn-sedimentary intra-basinal continental molasse sequences. The mafic and mafic-intermediate rocks belong to sub-alkaline tholeiitic series were separated in three groups (I–III) showing a high Th and Pb abundances, depletion in Nb, Ta and Sr, and slightly enriched in LREE patterns (LaN/YbN =1.4–4.4). Isotopically, the rocks of Group I have the initial ratios 87Sr/86Sr(i) =0.709351–0.707112, 143Nd/144Nd(i) =0.512490–0.512588 and high positive ɛ Nd270 values from 3.9 to 5.80; the rocks of Group II present for the initial ratios values 87Sr/86Sr(i) =0.709434–0.710092, 143Nd/144Nd(i) =0.512231–0.512210 and for ɛ Nd270 the negative values from −1.17 to −1.56; the rocks of Group III display for the initial ratios the values 87Sr/86Sr(i) =0.710751–0.709448, 143Nd/144Nd(i) =0.512347–0.512411 and for ɛ Nd270 the positive values from 1.64 to 2.35. The rocks resembling continental tholeiites, suggest a mantle origin and were further affected by fractionation and crustal contamination. In addition, the REE geochemistry (1>SmN/YbN <2.5; 0.9>LaN/SmN <2.5) suggests that these rocks were generated by high percentage partial melting of a metasomatized mantle in the garnet peridotite facies. The felsic rocks are enriched in Cs, Rb Th and U and depleted in Nb, Ta, Sr, Eu, and Ti. The REE fractionation patterns show a strong negative Eu anomaly (Eu/Eu*=0.23–0.40). The felsic rocks show the initial ratios the values: 87Sr/86Sr(i) =0.704096–0.707805, 143Nd/144Nd(i) =0.512012–0.512021 and for ɛ Nd270 the negative values from −5.27 to −5.44. They suggest to be generated within the lower crust during the emplacement of mantle-derived magmas that provided necessary heat to crustal partial melting. The mafic-intermediate and felsic rocks from Apuseni Mts represent a specific example of an association of bimodal volcanic rocks within a post-collisional extensional setting.


      PubDate: 2014-04-29T12:55:46Z
       
  • Editorial board members
    • Abstract: Publication date: March 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 1




      PubDate: 2014-04-29T12:55:46Z
       
  • Chemie der Erde/Geochemistry - farewell to the retired and welcome to the
           incoming of Editor-in-Chief
    • Abstract: Publication date: March 2014
      Source:Chemie der Erde - Geochemistry, Volume 74, Issue 1




      PubDate: 2014-04-29T12:55:46Z
       
  • 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
       
  • Silicate-bearing iron meteorites and their implications for the evolution
           of asteroidal parent bodies
    • Abstract: Publication date: Available online 14 January 2014
      Source:Chemie der Erde - Geochemistry
      Author(s): Alex Ruzicka
      Silicate-bearing iron meteorites differ from other iron meteorites in containing variable amounts of silicates, ranging from minor to stony-iron proportions (∼50%). These irons provide important constraints on the evolution of planetesimals and asteroids, especially with regard to the nature of metal–silicate separation and mixing. I present a review and synthesis of available data, including a compilation and interpretation of host metal trace-element compositions, oxygen-isotope compositions, textures, mineralogy, phase chemistries, and bulk compositions of silicate portions, ages of silicate and metal portions, and thermal histories. Case studies for the petrogeneses of igneous silicate lithologies from different groups are provided. Silicate-bearing irons were formed on multiple parent bodies under different conditions. The IAB/IIICD irons have silicates that are mainly chondritic in composition, but include some igneous lithologies, and were derived from a volatile-rich asteroid that underwent small amounts of silicate partial melting but larger amounts of metallic melting. A large proportion of IIE irons contain fractionated alkali-silica-rich inclusions formed as partial melts of chondrite, although other IIE irons have silicates of chondritic composition. The IIEs were derived from an H-chondrite-like asteroid that experienced more significant melting than the IAB asteroid. The two stony-iron IVAs were derived from an extensively melted and apparently chemically processed L or LL-like asteroid that also produced a metallic core. Ungrouped silicate-bearing irons were derived from seven additional asteroids. Hf–W age data imply that metal–silicate separation occurred within 0–10Ma of CAI formation for these irons, suggesting internal heating by 26Al. Chronometers were partly re-set at later times, mainly earlier for the IABs and later for the IIEs, including one late (3.60±0.15Ga) strong impact that affected the “young silicate” IIEs Watson (unfractionated silicate, and probable impact melt), Netschaëvo (unfractionated, and metamorphosed), and Kodaikanal (fractionated). Kodaikanal probably did not undergo differentiation in this late impact, but the similar ages of the “young silicate” IIEs imply that relatively undifferentiated and differentiated materials co-existed on the same asteroid. The thermal histories and petrogeneses of fractionated IIE irons and IVA stony irons are best accommodated by a model of disruption and reassembly of partly molten asteroids.


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


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


      PubDate: 2013-12-19T00:06:15Z
       
  • Editorial Board
    • Abstract: Publication date: December 2013
      Source:Chemie der Erde - Geochemistry, Volume 73, Issue 4




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


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


      PubDate: 2013-11-17T00:06:10Z
       
  • Chemical fluid transport (CFT) A window into Earth and its development
    • Abstract: Publication date: Available online 29 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): Werner Schrön
      Gas phase transport according to chemical fluid transport (CFT) in Earth's crust as well as in the solar nebula is characterized by very high transport efficiency. Systematic investigations of mobilization, transport and deposition of gaseous MeX (Me=metal, X=F or Cl) compounds by solid gas equilibrium reactions are suitable to explain numerous extensive accumulations of minerals and ores. More than 40 of the considered chemical elements form volatile MeX compounds. Some elements tend to form MeF compounds, whereas others are more likely to form MeCl compounds. Silicon reacts with HF to form SiF4 and replaces other elements to form MeF compounds at low temperature ranges. Accumulations caused by SiF4 transport explain the formation of numerous quartz varieties and silicate minerals in Earth's crust. Iron most likely reacts with HCl to form FeCl2 as well as FeCl3 and explain the formation of iron or iron compounds. Thermodynamically directed transport from cool to hot areas in connection with cyclic processes increases the transport efficiency of MeX-species. Such species are SiF4, Al2F6, POF3, Cu3Cl3, SnCl4, BF3, GeF4, GeCl4, Ga2Cl6, ZrF4, NbF5 and TiF4. The transport gases SiF4 and POF3 often react with environmental compounds forming pneumatolytic and metasomatical mineral accumulations. CFT is the “motor” of pneumatolytic and metasomatical processes. MeX compounds moving from hot to cool areas are FeCl2, FeCl3, MnCl2, NiCl2, CoCl2, WO2Cl2, MoO2Cl2, GeCl2, GaCl3, SnCl2. Their most spectacular products could be the Fe,Ni iron bodies (taenite/kamacite) known as iron meteorites. They were formed by cyclic processes as well. Thus taenite/kamacite formation by CFT could be an important argument for heterogeneous accretion. For MeX transport processes only halogen compounds HX and temperature gradients are necessary. All examples described here show that mobilization, transport and deposition of MeX compounds follow the same simple principles. In this way CFT can explain global mineral accumulations caused by gas phase transport. Therefore, all products of CFT should be named fluidic rocks (resp. fluidic minerals and ores) in contrast to igneous, sedimentary and metamorphic rocks. The concept “magmatic residual liquid” will be replaced by CFT. The CFT, described here, is possibly operative in interstellar clouds as well, as soon as F, Cl, Fe, Si and other chemical elements are present and the preconditions for CFT are fulfilled.


      PubDate: 2013-11-01T00:06:12Z
       
  • The Bizielle vein (valle de Gistain): a case of iron oxide transformations
           at the Pyrenees of Spain
    • Abstract: Publication date: Available online 15 October 2013
      Source:Chemie der Erde - Geochemistry
      Author(s): I. DeFelipe , I. Fanlo , E. Mateo , I. Subías
      The Bizielle vein has some unique features among the Pyrenean alpine veins that allow us to address the question of the nature of iron oxides transformations under low temperature hydrothermal conditions, which is well known to prevailed over wide areas of western Europe between early Triassic to early Cretaceous times. Isotopic studies indicate a deep-seated origin of the ore-forming fluids and suggest that the metals were leached from the Variscan basement (mainly from granites). Isotopic geothermometry and regional evidences point to a 250°C and reducing fluid, being SH2 the predominant S specie. Under such conditions, the proposed in situ deposition of hematite is a consequence of Fe carbonates dissolution and oxidation involving dissolution/precipitation processes in the sense of Putnis. Non-redox model is a quite plausible origin for subsequent hematite to magnetite conversion.


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


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


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


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


      PubDate: 2013-10-07T23:06:35Z
       
 
 
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