The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

An alternative approach using integrated gamma-ray and geochemical data to estimate the inputs to subduction zones from ODP Leg 185, Site 801

An alternative approach using integrated gamma-ray and geochemical data to estimate the inputs to subduction zones from ODP Leg 185, Site 801
An alternative approach using integrated gamma-ray and geochemical data to estimate the inputs to subduction zones from ODP Leg 185, Site 801
The goal of the subduction factory project is to obtain a better understanding of processes occurring at convergent margins and performs mass balance calculations for tracer elements. As part of this project, a major objective of ODP Leg 185 is to determine the chemical composition of the inputs to the West Pacific Subduction Factory for use in calculations of elemental mass balance across the subduction zone. To understand such elemental budgets, it is critical to know the lithological diversity and chemical characteristics of the down going oceanic plate. Hole 801C, located ocean-ward of the Mariana island arc system, is the most complete section of old oceanic crust sampled to date but, core recovery in basement holes is often poor (e.g., <30%) resulting in a bias such that the less altered material is preferentially recovered. Integration of drilled cores and downhole wire line logging data was performed to reconstruct a complete section of the drilled basement. Furthermore we integrate gamma ray logging data with the geochemical analyses of recovered cores to estimate the average composition, in terms of potassium and uranium, of the volcanic section in Hole 801C. We used FMS (Formation MicroScanner) images to relocate the samples with respect to the logging depth and to directly compare the logging data and the geochemical data. We demonstrate that the logging tool is well calibrated for K and U in the basement and that differences observed between K2O and U contents measured by the tool and by geochemistry are strongly dependent on the nature of the samples. The average K2O concentration of Hole 801C basement section is 0.34 wt.% using core-derived proportions, 0.51 wt.% using log-derived proportions and 0.47 wt.% using the gamma ray data. In the same manner the average U concentrations are respectively 0.34 ppm, 0.39 ppm and 0.42–0.5 ppm. This implies that K and U budgets recycled in the Mariana subduction zone are 20–50% higher than previously reported. These results demonstrate that a careful core-log-geochemical integration is essential to accurately estimate the composition of a drilled section and in order to better constraint chemical fluxes into subduction zones.
Subduction Factory, ODP Leg 185, core-log integration, geochemistry, K, U budgets.
1525-2027
Art. 08902
Revillon, S.
58bd2948-077d-436b-ba95-76ff59186db3
Barr, S.
2b0a6a50-0251-40d2-adfa-4c3001b1b1ca
Brewer, T.S.
c0b281f4-744a-4a10-ac12-0a7a6afd59fa
Harvey, P.K.
9399f469-3709-41d8-83df-5d08bb1a3eee
Tarney, J.
87a93f6d-95f2-44c4-9479-0f1047481e83
Revillon, S.
58bd2948-077d-436b-ba95-76ff59186db3
Barr, S.
2b0a6a50-0251-40d2-adfa-4c3001b1b1ca
Brewer, T.S.
c0b281f4-744a-4a10-ac12-0a7a6afd59fa
Harvey, P.K.
9399f469-3709-41d8-83df-5d08bb1a3eee
Tarney, J.
87a93f6d-95f2-44c4-9479-0f1047481e83

Revillon, S., Barr, S., Brewer, T.S., Harvey, P.K. and Tarney, J. (2002) An alternative approach using integrated gamma-ray and geochemical data to estimate the inputs to subduction zones from ODP Leg 185, Site 801. Geochemistry, Geophysics, Geosystems, 3 (12), Art. 08902. (doi:10.1029/2002GC000344).

Record type: Article

Abstract

The goal of the subduction factory project is to obtain a better understanding of processes occurring at convergent margins and performs mass balance calculations for tracer elements. As part of this project, a major objective of ODP Leg 185 is to determine the chemical composition of the inputs to the West Pacific Subduction Factory for use in calculations of elemental mass balance across the subduction zone. To understand such elemental budgets, it is critical to know the lithological diversity and chemical characteristics of the down going oceanic plate. Hole 801C, located ocean-ward of the Mariana island arc system, is the most complete section of old oceanic crust sampled to date but, core recovery in basement holes is often poor (e.g., <30%) resulting in a bias such that the less altered material is preferentially recovered. Integration of drilled cores and downhole wire line logging data was performed to reconstruct a complete section of the drilled basement. Furthermore we integrate gamma ray logging data with the geochemical analyses of recovered cores to estimate the average composition, in terms of potassium and uranium, of the volcanic section in Hole 801C. We used FMS (Formation MicroScanner) images to relocate the samples with respect to the logging depth and to directly compare the logging data and the geochemical data. We demonstrate that the logging tool is well calibrated for K and U in the basement and that differences observed between K2O and U contents measured by the tool and by geochemistry are strongly dependent on the nature of the samples. The average K2O concentration of Hole 801C basement section is 0.34 wt.% using core-derived proportions, 0.51 wt.% using log-derived proportions and 0.47 wt.% using the gamma ray data. In the same manner the average U concentrations are respectively 0.34 ppm, 0.39 ppm and 0.42–0.5 ppm. This implies that K and U budgets recycled in the Mariana subduction zone are 20–50% higher than previously reported. These results demonstrate that a careful core-log-geochemical integration is essential to accurately estimate the composition of a drilled section and in order to better constraint chemical fluxes into subduction zones.

This record has no associated files available for download.

More information

Published date: 2002
Keywords: Subduction Factory, ODP Leg 185, core-log integration, geochemistry, K, U budgets.

Identifiers

Local EPrints ID: 1262
URI: http://eprints.soton.ac.uk/id/eprint/1262
ISSN: 1525-2027
PURE UUID: c9fce7a5-c0c8-44d2-b984-45ce67812072

Catalogue record

Date deposited: 07 Apr 2004
Last modified: 09 Nov 2021 06:04

Export record

Altmetrics

Contributors

Author: S. Revillon
Author: S. Barr
Author: T.S. Brewer
Author: P.K. Harvey
Author: J. Tarney

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.

×