Complex cementation textures and authigenic mineral assemblages in Recent concretions from the Lincolnshire Wash (east coast, UK) driven by Fe(0) to Fe(II) oxidation

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doi: 10.1144/gsjgs.152.1.0157
Authors:Al-Agha, M. R.; Burley, S. D.; Curtis, C. D.; Esson, J.
Author Affiliations:Primary:
University of Manchester, Diagenesis Research Group, Manchester, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, Vol.152 (Part 1), p.157-171. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1995
Note:In English. 57 refs.; illus., incl. sects., 1 table, geol. sketch maps
Summary:Petrographic observations indicate that cements within concretions in these modern intertidal sediments were precipitated in a distinct sequence around a metallic nucleus (relict military armaments and shrapnel fragments), arranged from core to periphery: a) a ferrous hydroxy chloride (similar in bulk to akaganeite) together with iron monosulphide (amorphous and mackinawite), pyrite and possibly native sulphur, b) ferroan carbonate cements (including siderite, ankerite and calcite, c) mixed ferrous and ferric minerals ('green rust', magnetite and possibly greigite), d) fully oxidized minerals, including akaganeite, goethite, hematite, gypsum and a complex basic sulphate of Fe, Ca, Mg, Si and Al. The initiating reaction for precipitation of these cements is anaerobic corrosion of iron at zero valence state with sulphate as an oxidant: 4Fe° + SO 2- 4 + 4H2O ->> 3Fe(OH)2 + 2OH- + FeS. Further away from the metallic nucleus, carbonates cement the host clastic sediment. The cementation process in these concretions is driven by the extreme instability of metallic iron in contact with saline, anaerobic water and is indicative more of cathodic corrosion than the growth of ancient carbonate-sulphide concretions. [R.A.H.]
Subjects:Authigenic minerals; Cementation; Coastal environment; Concretions; Diagenesis; Ferrous iron; Intertidal environment; Iron; Metals; Oxidation; Secondary structures; Sedimentary structures; Textures; England; Europe; Great Britain; Lincolnshire England; United Kingdom; Western Europe
Abstract Numbers:95M/3132
Record ID:1995036980
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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