The University of Southampton
University of Southampton Institutional Repository

Magnetite dissolution in siliceous sediments

Florindo, F., Roberts, A.P. and Palmer, M.R. (2003) Magnetite dissolution in siliceous sediments Geochemistry, Geophysics, Geosystems, 4, (7), Art.1053-[13]. (doi:10.1029/2003GC000516).

Record type: Article

Abstract

Magnetite dissolution, and consequent loss of magnetization, is widely observed in reducing sedimentary environments, where the decrease in Eh-pH values with depth is driven by bacterially mediated degradation of organic carbon. We have observed low magnetizations in sediments with elevated pore water silica concentrations that arise from diagenesis of biogenic silica and/or silicic volcanic ash. These depletions in magnetization are greater than can be accounted for by dilution with magnetite-poor sediments and suggest that postdepositional destruction of magnetite has occurred. Biosiliceous sediments usually also contain elevated concentrations of organic carbon, which makes it difficult to separate organic-carbon-related magnetite dissolution from other possible mechanisms for magnetite dissolution. However, the extent of magnetite dissolution in the sedimentary sequences that we have studied is not obviously related to the redox-state of the environment. This suggests that other mechanisms might have given rise to magnetite dissolution in these siliceous sediments. Thermodynamic calculations indicate that magnetite is unstable under conditions of elevated dissolved silica concentrations (and appropriate Eh-pH conditions) and predict that magnetite will break down to produce iron-bearing smectite. A survey of magnetic susceptibility and pore water geochemical data from widely distributed Ocean Drilling Program sites supports this observed link between high dissolved silica concentrations and low magnetic susceptibilities. This observed link also holds for environments with low biogenic silica productivity (and low organic carbon content) but with high interstitial silica concentrations due to dissolution of silicic volcanic ashes. Dissolution of magnetite is therefore predicted to be a common feature of siliceous sedimentary environments.

Full text not available from this repository.

More information

Published date: 2003
Keywords: magnetite, dissolution, silica, siliceous sediments, diagenesis, smectite

Identifiers

Local EPrints ID: 1287
URI: http://eprints.soton.ac.uk/id/eprint/1287
ISSN: 1525-2027
PURE UUID: 1d910c84-455d-40b3-a192-c8b94ef31ff2

Catalogue record

Date deposited: 27 Apr 2004
Last modified: 17 Jul 2017 17:17

Export record

Altmetrics

Contributors

Author: F. Florindo
Author: A.P. Roberts
Author: M.R. Palmer

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×