Rates of carbonate cementation associated with sulphate reduction in DSDP/ODP sediments; implications for the formation of concretions

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doi: 10.1016/j.chemgeo.2004.06.020
Author(s): Raiswell, R.; Fisher, Q. J.
Author Affiliation(s): Primary:
University of Leeds, School of Earth Sciences, Leeds, United Kingdom
Volume Title: Chemical Geology
Source: Chemical Geology, 211(1-2), p.71-85. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541 CODEN: CHGEAD
Note: In English. 61 refs.; illus., incl. 2 tables
Summary: DSDP/ODP porewater profiles in organic carbon-bearing (<5% org. C) sediments commonly show decreases in Ca2+ concentrations and increases in alkalinity over depths where sulphate is being removed by microbial reduction. These Ca2+ depletion profiles represent the combined effect of diffusion, advection and reaction (addition by ion exchange and removal by precipitation mainly as CaCO3 and/or dolomite). A diagenetic model has been used to estimate the rate constant (k) for Ca2+ removal by precipitation during sulphate depletion over depths of 15-150 m, assuming first order kinetics. The rate constants for Ca2+ removal range from 10-14 to 10-11 s-1 in 19 DSDP/ODP sediments, which span a range of bottom water temperatures (0-10°C), lithologies (calcareous to clastic) and sedimentation rates (0.001-0.4 cm year-1). Values of k correlate with sedimentation rate (ω) such that log k = 1.16 log ω-10.3, indicating that faster rates of Ca2+ removal occur at higher sedimentation rates where there are also higher degrees of saturation with respect to CaCO3 and dolomite. Depth-integrated masses of Ca2+ removed (<100 µmol cm-2) during sulphate depletion over these depth ranges are equivalent to a dispersed phase of approximately 1.5 wt.% CaCO3 or 3 wt.% dolomite in a compacted sediment. The complete occlusion of sediment porosity observed in concretions with isotopic signatures suggesting carbonate sourced from sulphate reduction therefore requires more time (a depositional hiatus), more rapid sulphate reduction (possibly by anaerobic methane oxidation) and/or the continued transport of isotopically light carbonate to the concretion site after sulphate reduction has ceased. Abstract Copyright (2004) Elsevier, B.V.
Year of Publication: 2004
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 07 Marine Geology and Oceanography; Algae; Amazon Fan; Arabian Sea; Arctic Ocean; Atlantic Ocean; Blake-Bahama Outer Ridge; Carbonate sediments; Carbonates; Cementation; Cenozoic; Chemical reactions; Concretions; Coral Sea; Deep Sea Drilling Project; Diagenesis; Diatoms; Diffusion; East Pacific; Foraminifera; Genesis; Great Barrier Reef; Guaymas Basin; Gulf of California; Indian Ocean; Invertebrata; Japan Sea; Kinetics; Marine geology; Marine sediments; Mathematical methods; Microfossils; Middle America Trench; Nannofossils; Nodules; North Atlantic; North Pacific; Northeast Pacific; Northwest Pacific; Ocean Drilling Program; Oki Ridge; Pacific Ocean; Plantae; Porosity; Protista; Quaternary; Reduction; Secondary structures; Sedimentary structures; Sedimentation; Sedimentation rates; Sediments; South Pacific; Southwest Pacific; Sulfates; West Pacific; Yermak Plateau
Record ID: 2005028422
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

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