The University of Southampton
University of Southampton Institutional Repository

Authigenic or detrital origin of pyrrhotite in sediments?: resolving a paleomagnetic conundrum

Authigenic or detrital origin of pyrrhotite in sediments?: resolving a paleomagnetic conundrum
Authigenic or detrital origin of pyrrhotite in sediments?: resolving a paleomagnetic conundrum
Monoclinic pyrrhotite (Fe7S8) is widely claimed to carry magnetizations acquired during early diagenesis in anoxic sedimentary environments. In contrast, geochemical literature indicates that pyrrhotite formation is extremely slow below 180 °C, which makes it a highly unlikely carrier of early diagenetic remanences in sediments. This view is confirmed by the occurrence of late diagenetic Fe7S8 in ancient sediments and the general lack of Fe7S8 in modern sediments. Horng et al. [C.S. Horng, M. Torii, K.S. Shea, S.J. Kao, Inconsistent magnetic polarities between greigite- and pyrrhotite/magnetite-bearing marine sediments from the Tsailiao-chi section, southwestern Taiwan, Earth Planet. Sci. Lett. 164 (1998) 467–481.] documented the presence of Fe7S8 that carries a magnetic signal indistinguishable from that of detrital magnetite in Pleistocene marine sediments from Taiwan. We tested the possibility that the Fe7S8 could have a detrital origin by conducting a source-to-sink study and found Fe7S8 in metamorphic rocks of the Taiwan Central Range and in material eroded from these rocks in the transportation pathway and in the depositional sink. This confirms that the Fe7S8 has a detrital origin. Rapid transportation from source to sink (e.g., by typhoon-associated flood events) probably assists preservation of the Fe7S8, which might otherwise oxidize during transportation. The widespread occurrence of exhumed metamorphic rocks in orogenic belts around the world makes them a likely source of Fe7S8 in marginal sedimentary basins. Detrital Fe7S8 should therefore be more routinely considered to be responsible for paleomagnetic records when it is present in sediments with partial metamorphic provenance.
pyrrhotite, monoclinic, hexagonal, iron sulphide, authigenic, detrital, diagenesis
0012-821X
750-762
Horng, C-S.
2961ce90-a6c3-4b7f-b464-a2a9fb507ea9
Roberts, A.P.
4497b436-ef02-428d-a46e-65a22094ba52
Horng, C-S.
2961ce90-a6c3-4b7f-b464-a2a9fb507ea9
Roberts, A.P.
4497b436-ef02-428d-a46e-65a22094ba52

Horng, C-S. and Roberts, A.P. (2006) Authigenic or detrital origin of pyrrhotite in sediments?: resolving a paleomagnetic conundrum. Earth and Planetary Science Letters, 241 (3-4), 750-762. (doi:10.1016/j.epsl.2005.11.008).

Record type: Article

Abstract

Monoclinic pyrrhotite (Fe7S8) is widely claimed to carry magnetizations acquired during early diagenesis in anoxic sedimentary environments. In contrast, geochemical literature indicates that pyrrhotite formation is extremely slow below 180 °C, which makes it a highly unlikely carrier of early diagenetic remanences in sediments. This view is confirmed by the occurrence of late diagenetic Fe7S8 in ancient sediments and the general lack of Fe7S8 in modern sediments. Horng et al. [C.S. Horng, M. Torii, K.S. Shea, S.J. Kao, Inconsistent magnetic polarities between greigite- and pyrrhotite/magnetite-bearing marine sediments from the Tsailiao-chi section, southwestern Taiwan, Earth Planet. Sci. Lett. 164 (1998) 467–481.] documented the presence of Fe7S8 that carries a magnetic signal indistinguishable from that of detrital magnetite in Pleistocene marine sediments from Taiwan. We tested the possibility that the Fe7S8 could have a detrital origin by conducting a source-to-sink study and found Fe7S8 in metamorphic rocks of the Taiwan Central Range and in material eroded from these rocks in the transportation pathway and in the depositional sink. This confirms that the Fe7S8 has a detrital origin. Rapid transportation from source to sink (e.g., by typhoon-associated flood events) probably assists preservation of the Fe7S8, which might otherwise oxidize during transportation. The widespread occurrence of exhumed metamorphic rocks in orogenic belts around the world makes them a likely source of Fe7S8 in marginal sedimentary basins. Detrital Fe7S8 should therefore be more routinely considered to be responsible for paleomagnetic records when it is present in sediments with partial metamorphic provenance.

This record has no associated files available for download.

More information

Published date: 2006
Keywords: pyrrhotite, monoclinic, hexagonal, iron sulphide, authigenic, detrital, diagenesis

Identifiers

Local EPrints ID: 44794
URI: http://eprints.soton.ac.uk/id/eprint/44794
ISSN: 0012-821X
PURE UUID: 08fe1fc1-ede2-41a8-b68e-63b34a73a5dc

Catalogue record

Date deposited: 15 Mar 2007
Last modified: 15 Mar 2024 09:08

Export record

Altmetrics

Contributors

Author: C-S. Horng
Author: A.P. Roberts

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.

×