Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions

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doi: 10.1016/0016-7037(86)90085-2
Authors:Curtis, C. D.; Coleman, M. L.; Love, L. G.
Author Affiliations:Primary:
Univ. Sheffield, Dep. Geol., Sheffield, United Kingdom
BP Res. Cent., United Kingdom
Volume Title:Geochimica et Cosmochimica Acta
Source:Geochimica et Cosmochimica Acta, 50(10), p.2321-2334. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037
Publication Date:1986
Note:In English. 34 refs.; illus. incl. 1 table
Summary:Samples of 11 concretions were collected from the Lower Westphalian A at Bullhouse Quarry, near Penistone, Yorkshire, Cored, whole-rock sections were analysed by XRD, and for CO2, P2O5 and porosity, and the carbonate components were analysed for Fe, Mg, Ca, Mn, delta 13C and delta 18O. The concretions consist essentially of siderite, dolomite, ankerite, calcite and pyrite. For C- and O-isotopic analysis, samples were reacted with phosphoric acid in vacuum, to release CO2 from the carbonate, and the gas evolved was analysed by MS. The calcite/pyrite, dolomite/pyrite, and siderite samples vary in delta 13C (< +10.35 to > -21.49per mille) and in major Ca, Mg, Fe and Mn. Fe/Mg decreases systematically from centres to edges of the concretions. Calcite/pyrite and dolomite/pyrite concretions developed completely prior to significant burial, and have high Mn/Fe ratios but negative delta 13C values: calcite - 21.49per mille, dolomite -8.67 to -10.48per mille. On the basis of pore- water evolution in modern sediments, microbial processes of sulphate reduction and methanogenesis, with thermal decarboxylation, were responsible for the precipitation of these minerals. Mn(IV) and Fe(III) acted differently as oxidants producing CO2 and increasing alkalinity. Mineral type (Fe sulphide or carbonate), isotopic and mineral chemistry, were controlled by fresh or marine depositional waters, governing the presence or absence of sulphate reduction. [R.K.H.]
Subjects:Authigenic minerals; Biogenic processes; Burial diagenesis; C-13/C-12; Calcite; Carbon; Carbonates; Carboniferous; Clastic rocks; Coal seams; Concretions; Diagenesis; Dolomite; Effects; Geochemistry; Isotopes; Minerals; Organic compounds; Paleozoic; Pore water; Secondary structures; Sedimentary rocks; Sedimentary structures; Siderite; Stable isotopes; Upper Carboniferous; Westphalian; England; Europe; Great Britain; Pennines; United Kingdom; Western Europe; Organic materials
Abstract Numbers:87M/2774
Record ID:1987022080
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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