Details
| Original language | English |
|---|---|
| Pages (from-to) | 63-77 |
| Number of pages | 15 |
| Journal | Chemical geology |
| Volume | 306-307 |
| Publication status | Published - 4 May 2012 |
Abstract
Studying diffusive transport in porous rocks is of fundamental importance in understanding a variety of geochemical processes including: element transfer, primary mineral dissolution kinetics and precipitation of secondary phases. Here we report new findings on the relationship between diffusive transport and textural characteristics of the pore systems on the example of mid-oceanic ridge basalts having different degree of alteration but very similar bulk pore volume. Diffusion processes in porous basalts were studied in situ using H 2O→D 2O exchange experiments. The effective diffusion coefficients of water molecules increase systematically from 5.05.10 -11 to 1.19.10 -10m 2/s for fresh and moderately altered basalts and from 2.40.10 -11 to 6.72.10 -11m 2/s for completely altered basalt as temperature increases from 5 to 50°C. The activation energy of the diffusion process increases from 12.29±0.71kJ/mol for fresh and moderately altered basalts to 14.3±1.33kJ/mol for completely altered basalt. The results indicate that neither the bulk porosity nor the degree of alteration can be used as proxies for the efficiency of element transport during MORB-water interaction. The formation of secondary phases that replace primary minerals and fill the pore space in the rock leads to the formation of tiny pores and phases with large specific surface area. These factors might have a dominant control on the transport properties of altered basaltic rocks.
Keywords
- Activation energy, Alteration, Diffusion coefficients, Diffusive transport, Mid-ocean ridge basalts, Porosity
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Chemical geology, Vol. 306-307, 04.05.2012, p. 63-77.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Diffusive transport of water in porous fresh to altered mid-ocean ridge basalts
AU - Simonyan, Anna V.
AU - Dultz, Stefan
AU - Behrens, Harald
N1 - Funding information: The assistance of O. Diedrich for the preparation of the samples and R. M. Klatt for the analyses of the samples by SEM is gratefully acknowledged. We thank A. Bell for correction of English and helpful comments. Two anonymous reviewers are acknowledged for their comments. This study was supported by the German Science Foundation (DFG) under the contract numbers Du 271/3-1, 2 and Be 1720/17-1, 2 .
PY - 2012/5/4
Y1 - 2012/5/4
N2 - Studying diffusive transport in porous rocks is of fundamental importance in understanding a variety of geochemical processes including: element transfer, primary mineral dissolution kinetics and precipitation of secondary phases. Here we report new findings on the relationship between diffusive transport and textural characteristics of the pore systems on the example of mid-oceanic ridge basalts having different degree of alteration but very similar bulk pore volume. Diffusion processes in porous basalts were studied in situ using H 2O→D 2O exchange experiments. The effective diffusion coefficients of water molecules increase systematically from 5.05.10 -11 to 1.19.10 -10m 2/s for fresh and moderately altered basalts and from 2.40.10 -11 to 6.72.10 -11m 2/s for completely altered basalt as temperature increases from 5 to 50°C. The activation energy of the diffusion process increases from 12.29±0.71kJ/mol for fresh and moderately altered basalts to 14.3±1.33kJ/mol for completely altered basalt. The results indicate that neither the bulk porosity nor the degree of alteration can be used as proxies for the efficiency of element transport during MORB-water interaction. The formation of secondary phases that replace primary minerals and fill the pore space in the rock leads to the formation of tiny pores and phases with large specific surface area. These factors might have a dominant control on the transport properties of altered basaltic rocks.
AB - Studying diffusive transport in porous rocks is of fundamental importance in understanding a variety of geochemical processes including: element transfer, primary mineral dissolution kinetics and precipitation of secondary phases. Here we report new findings on the relationship between diffusive transport and textural characteristics of the pore systems on the example of mid-oceanic ridge basalts having different degree of alteration but very similar bulk pore volume. Diffusion processes in porous basalts were studied in situ using H 2O→D 2O exchange experiments. The effective diffusion coefficients of water molecules increase systematically from 5.05.10 -11 to 1.19.10 -10m 2/s for fresh and moderately altered basalts and from 2.40.10 -11 to 6.72.10 -11m 2/s for completely altered basalt as temperature increases from 5 to 50°C. The activation energy of the diffusion process increases from 12.29±0.71kJ/mol for fresh and moderately altered basalts to 14.3±1.33kJ/mol for completely altered basalt. The results indicate that neither the bulk porosity nor the degree of alteration can be used as proxies for the efficiency of element transport during MORB-water interaction. The formation of secondary phases that replace primary minerals and fill the pore space in the rock leads to the formation of tiny pores and phases with large specific surface area. These factors might have a dominant control on the transport properties of altered basaltic rocks.
KW - Activation energy
KW - Alteration
KW - Diffusion coefficients
KW - Diffusive transport
KW - Mid-ocean ridge basalts
KW - Porosity
UR - http://www.scopus.com/inward/record.url?scp=84858719691&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2012.02.017
DO - 10.1016/j.chemgeo.2012.02.017
M3 - Article
AN - SCOPUS:84858719691
VL - 306-307
SP - 63
EP - 77
JO - Chemical geology
JF - Chemical geology
SN - 0009-2541
ER -