Distribution and partitioning of major and trace elements in pyrite-bearing sediments of a Mediterranean coastal lagoon |
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| Institution: | 1. DiSPUTer, Università G. d''Annunzio, Campus Madonna delle Piane, Via dei Vestini, 66100 Chieti, Italy;2. Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada;3. British Columbia Geological Survey, PO Box 9333 Stn Prov Gov''t, 5th Floor 1810 Blanshard St., Victoria, British Columbia V8W9N3, Canada;4. MV Geologia, v. Macera 8, Tivoli, Italy;1. Departamento de Didáctica de las Ciencias Experimentales, Universidad de Granada, Facultad de Ciencias de la Educación, Campus de Cartuja, 18071 Granada, Spain;2. Instituto Andaluz de Ciencias de la Tierra (CSIC, Universidad de Granada), Avda. de las Palmeras 4, 18100 Armilla, Granada, Spain;3. Scottish Universities Environmental Research Centre (SUERC), East Kilbride, Glasgow G75 0QF, Scotland, United Kingdom;4. Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Avd. Fuentenueva s/n, 18002 Granada, Spain;5. Departamento de Geology, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile;6. Andean Geothermal Center of Excellence (CEGA-FONDAP), Universidad de Chile, Plaza Ercilla 803, Santiago, Chile;7. School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, European Way, SO14 3ZH, United Kingdom |
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| Abstract: | The formation of iron sulphide minerals exerts significant control on the behaviour of trace elements in sediments. In this study, three short sediment cores, retrieved from the remote Antinioti lagoon (N. Kerkyra Island, NW Greece), are investigated concerning the solid phase composition, distribution, and partitioning of major (Al, Fe) and trace elements (Cd, Cu, Mn, Pb, and Zn). According to 210Pb, the sediments sampled correspond to depositions of the last 120 years. The high amounts of organic carbon (4.1–27.5%) result in the formation of Fe sulphides, predominantly pyrite, already at the surface sediment layers. Pyrite morphologies include monocrystals, polyframboids, and complex FeS–FeS2 aggregates. According to synchrotron-generated micro X-ray fluorescence and X-ray absorption near-edge structure spectra, authigenically formed, Mn-containing, Fe(III) oxyhydroxides (goethite type) co-exist with pyrite in the sediments studied. Microscopic techniques evidence the formation of galena, sphalerite and CuS, whereas sequential extractions show that carbonates are important hosts for Mn, Cd, and Zn. However, significant percentages of non-lattice held elements are bound to Fe/Mn oxyhydroxides that resist reductive dissolution (on average 60% of Pb, 46% of Cd, 43% of Zn and 9% of Cu). The partitioning pattern changes drastically in the deeper part of the core that is influenced by freshwater inputs. In these sediments, the post-depositional pyritization mechanism, illustrated by overgrowths of Fe monosulphides on pre-existing pyrite grains, results in relatively high degree of pyritization that reaches 49% for Cd, 66% for Cu, 32% for Zn and 7% for Pb. |
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| Keywords: | Lagoon sediments Mediterranean sea Sequential extractions Diagenesis Framboidal pyrite Sulphides Degree of pyritization Synchrotron micro X-ray spectroscopy |
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