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Electrical resistivity, seismic velocity, and porosity of crustal rocks from the Oman ophiolite under brine-saturated ocean floor conditions.

Authors :
Tanimoto, Kazumasa
Akamatsu, Yuya
Katayama, Ikuo
Source :
Lithos. Apr2024, Vol. 470, pN.PAG-N.PAG. 1p.
Publication Year :
2024

Abstract

In order to examine the effects of crack properties on electrical resistivity and seismic velocity, we conducted simultaneous measurements of electrical resistivity, seismic velocity and porosity at brine-saturated hydrostatic pressures using mafic crustal rocks from the Oman ophiolite. The resistivity and velocity of the samples increase systematically with increasing confining pressure owing to the closure of cracks, as monitored by changes in porosity. Apparent formation factors of each sample are related to the porosity, but nonlinear relationships on logarithmic plots indicate that Archie's law cannot explain these experimental data. We evaluated the effect of crack porosity and aspect ratio for the measured velocity based on the effective medium theory, and the electrical resistivity was inferred from the crack porosity and connectivity according to the percolation model. The experimental velocity and resistivity results are consistent with the model calculations in terms of crack density, aspect ratio and connectivity. We applied a combined velocity-resistivity model to the geophysical logging and borehole data for the oceanic crust in Hole 504B. Our inversion results indicate that the seismic layer 2/3 transition is primarily caused by an alteration front controlled by interconnected cracks and fluid flow in the oceanic crust. • Electrical resistivity and seismic velocity of the Oman crustal sample were measured. • Joint model for electrical resistivity and seismic velocity was proposed. • Seismic layer 2/3 transition reflects a combination of crack and alterations. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00244937
Volume :
470
Database :
Academic Search Index
Journal :
Lithos
Publication Type :
Academic Journal
Accession number :
175960916
Full Text :
https://doi.org/10.1016/j.lithos.2024.107500