Seismic Velocities, Electrical Resistivities, Densities, and Porosities of Basalts from DSDP Leg 46

Christensen, N.I.; Hyndman, R.D.; Hull, J.M.; Salisbury, M.H.

doi:10.2973/dsdp.proc.46.129.1979

Cited by 7 publications

(11 citation statements)

References 8 publications

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“…The basalt's formation-porosity relationships agree fairly well with those for material collected on Legs 46 and 51, 52, 53, and, to a lesser degree, Leg 37, if the pertinent data are replotted and a comparison is made using only the F = Φ~m relationship: for Leg 37 (Hyndman and Drury, 1977), typical m is about 2.5; for Leg 46 (Christensen et al, 1979), typical m is about 1.9 (Kirkpatrick's 1979 logging data appear to be anomalous, perhaps because his density-porosity data are not quantitative enough); and for Legs 51, 52, 53 Hamano, 1980), typical m is about 1.9. Figure 14, because there is not necessarily a corresponding horizontal velocity for each vertical velocity.…”

Section: Scatter Diagramssupporting

confidence: 54%

“…Other possible reasons for the difference in Leg 37 data are that (1) the induction log measured resistivity in a direction parallel to bedding; (2) different techniques were used in measuring the resistivity-Leg 37 data were laboratory-determined; (3) logs were incorrect; or (4) Site 462 basalts have greater pore-water salinities than one would expect. In general, it appears that the resistivities meas- ured by well logs tend to be lower in absolute value than the laboratory-measured resistivities; this seems to result from the logs including cracks and fractures in their sampling, as suggested by Christensen et al (1979), Kirkpatrick (1979), and Salisbury et al (1980), but also, in part, from the induction log resistivity being measured parallel to bedding. In Figure 20, formation factor versus porosity, the Archie (1942) equations agree with the data.…”

Section: Scatter Diagramsmentioning

confidence: 94%

“…Most sediments or rocks are not accurately defined, however, by this simple model. Sediments or rocks generally have irregularly shaped grains, so that conducting ions must travel a longer average path than would be required between spherical particles, and sediments or rocks will therefore have greater resistivities and formation factors than those derived by Maxwell's (1904) equation . Among DSDP cruises, the following have resulted in published electrical resistivities of water-saturated basalt: Leg 26 (Hyndman and Ade-Hall, 1974); Leg 34 (Drury, 1976); Leg 37 (Hyndman and Drury, 1977;Katsube et al, 1977); Leg 46 (Christensen et al, 1979;Kirkpatrick, 1979); and Legs 51, 52, 53 Hamano, 1980;Salisbury et al, 1980). We will interpret the DSDP Hole 462 density and electrical logs by using a technique developed by the petroleum industry (Schlumberger, Ltd., 1972) called the "apparent electrical resistivity of the interstitial water" (R wa curve).…”

Section: Electrical Resistivitymentioning

confidence: 99%

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Electrical Resistivity, Sound Velocity, Thermal Conductivity, Density-Porosity, and Temperature, Obtained by Laboratory Techniques and Well Logs: Site 462 in the Nauru Basin of the Pacific Ocean

Boyce¹

1981

Initial Reports of the Deep Sea Drilling Project

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At Deep Sea Drilling Project (DSDP) Site 462, from mudline to 447 meters below the sea floor, Cenozoic nannofossil oozes and chalks have acoustic anisotropies such that horizontal sonic velocities are 0 to 2.5% faster than those in the vertical direction. In laminated chalk, anisotropy of 5% is typical, and in limestones, radiolarian oozes, porcellanites, and cherts, the anisotropies range from 4 to 13%. Middle Maestrichtian volcaniclastics from 447 meters to 560 meters below the sea floor have an acoustic anisotropy of 2 to 32%; 4 to 13% is typical. Basalt flows and sills occur between 560 meters and 1068 meters, and have no apparent anisotropy, but minor interbedded volcaniclastics have anisotropies from 0 to 20% (5% is typical). These volcaniclastics frequently have very small anisotropies, however, compared with the volcaniclastic sequence above the basalt section.Data in cross-plots of the laboratory-measured compressional sound velocity versus wet-bulk density, wet-water content, and porosity of sediments and sedimentary rock typically lie between the equations derived by Wyllie et al. (1956) and Wood (1941); the Wyllie et al. (1956) equation has a fair fit with similar basalt velocity cross-plots. Crossplots of thermal conductivity and sound velocity indicate only a fair correlation. Cross-plots of thermal conductivity versus porosity, wet-water content, and wet-bulk density correlate well with equations derived by Maxwell (1904), Ratcliff (1960), Parasnis (1960), and Bullard and Day (1961). Electrical formation factor versus porosity for sediments and sedimentary rock agrees with the Archie (1942) equation, with m values of 2.6; for basalt, an m of about 2.1 is typical. Basalt pore-water resistivities do not appear to be greatly different from sea water. Formation factors are greater than those derived from equations in Maxwell (1904), Winsauer et al. (1952), Boyce (1968), and Kermabon et al. (1969). An "apparent interstitial water resistivity" (i?J curve was derived from the density and induction logs. This R wa curve indicated an anomaly, at 393.5 to 396.5 meters, which could be interpreted as (1) 76% hydrocarbons, (2) relatively fresh pore water (1.8‰ salinity), or (3) low-grain-density (2.2 g/cm 3 ) semi-lithified porcellanite-chert. Porcellanite-chert is the most plausible interpretation.In situ temperatures measured by the Uyeda temperature probe were about 2 to 5°C (50%) higher than the equilibrium temperature (Lachenbruch and Brewer, 1959) extrapolated from two Gearhart-Owen continuous temperature logs; this discrepancy probably arises because the hole was washed out in this depth interval, so these extrapolated temperatures are probably not reliable. If one ignores all precautions as to temperature artifacts, then the equilibrium temperatures of the Gearhart-Owen temperature logs suggest that hydrothermal circulation is occurring in at least the upper 40 meters of the basalt section and heat is transferred by convection and not conduction. Hydrothermal circulation is probably not indica...

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Section: Scatter Diagramssupporting

confidence: 54%

Section: Scatter Diagramsmentioning

confidence: 94%

Section: Electrical Resistivitymentioning

confidence: 99%

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Electrical Resistivity, Sound Velocity, Thermal Conductivity, Density-Porosity, and Temperature, Obtained by Laboratory Techniques and Well Logs: Site 462 in the Nauru Basin of the Pacific Ocean

Boyce¹

1981

Initial Reports of the Deep Sea Drilling Project

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“…A third is a set of laboratory measurements of physical properties, including porosities, wet bulk densities, and P wave velocities measured at confining pressures of 20 and 600 MPa, in a suite of 188 basalt samples recovered by drilling at a variety of sites [Christensen et al, 1979[Christensen et al, , 1980[Christensen et al, , 1989Christensen and Lewis, 1983;Wilkens et al, 1983]. The fourth is a set of lab data for 84 diabase samples from Hole 504B [Christensen and Salisbury, 1985;Iturrino et al, 1995;Salisbury et al, 1996].…”

Section: Data Setsmentioning

confidence: 99%

The effects of alteration and porosity on seismic velocities in oceanic basalts and diabases

Carlson

2014

Geochem Geophys Geosyst

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Seismic velocities in the lavas that cap normal oceanic crust are affected by both crack porosity and alteration of the primary mineral phases, chiefly to clays. Porosity accounts for 75-80% of the velocity variation in sonic log velocities in the lava sections of Holes 504B and 1256D, but the effect of alteration on the properties of the basalts has not been assessed. In this analysis, the grain velocities in basalt and diabase samples are estimated from an empirical linear relationship between grain density and the P wave modulus. The theoretical velocity in fresh, zero-porosity basalt, or diabase is 6.96 6 0.07 km/s. Grain velocities in the diabase samples are statistically indistinguishable from the theoretical velocity, and show no variation with depth; alteration does not significantly affect the velocities in the diabase samples from Hole 504B. This result is consistent with previous analyses, which demonstrated that velocities in the dikes are controlled by crack porosity. In basalt lab samples, alteration reduces the average sample grain velocity to 6.74 6 0.02 km/s; cracks at the sample scale further reduce the velocity to 5.86 6 0.03 km/s, and large-scale cracks in the lavas reduce the average in situ velocity to 5.2 6 0.3 km/s. Cracks account for nearly 90% of the difference between seismic (in situ) velocities and the theoretical velocity in the unaltered solid material. Basalt grain velocities show a small, but significant systematic increase with depth; the influence of alteration decreases with depth in the lavas, reaching near zero at the base of the lavas in Holes 504B and 1256D.

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“…Deep-sea basalt core samples for which the porosity is largely vesicular and thus poorly connected give values of a = 1 and m = 2 or slightly greater (Hyndman et al, this volume;Christensen et al, 1979). There is, however, considerable uncertainty in these values because of the difficulties involved in sample porosity measurement and the difficulty of resaturating the samples if they were ever allowed to dry before the resistivity measurements were made.…”

Section: Formation Porosity From Resistivity Logmentioning

confidence: 99%

The Physical Nature of Young Upper Oceanic Crust on the Mid-Atlantic Ridge, Deep Sea Drilling Project Hole 395A

Hyndman¹,

Salisbury²

1984

Initial Reports of the Deep Sea Drilling Project

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The physical nature of the upper oceanic crust at DSDP Site 395 on the Mid-Atlantic Ridge was studied on Leg 78B using laboratory measurements on core and water samples; a suite of conventional downhole logs; and a series of special logs, downhole measurements and experiments, including a downhole magnetic log, temperature logs, a televiewer log, in situ permeability and aquifer pressure measurements with a downhole packer; and a seismic refraction experiment involving a downhole seismometer and ocean-bottom seismographs. Langseth et al. (this volume) provide a synthesis of the implications of the resulting data for the hydrogeology of the ocean crust at the site. This chapter provides a synthesis of the physical properties of the upper crust at the site over a range of physical scales. A marked change in porosity, electrical resistivity, compressional-and shear-wave velocity, thermal properties, and permeability at a subbasement depth of 400 m suggests that Hole 395A penetrated the Layer 2B/2C transition. An improved definition and interpretation of the crustal lithology penetrated by the hole, as determined by the downhole measurements, is also presented.

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Seismic Velocities, Electrical Resistivities, Densities, and Porosities of Basalts from DSDP Leg 46

Cited by 7 publications

References 8 publications

Electrical Resistivity, Sound Velocity, Thermal Conductivity, Density-Porosity, and Temperature, Obtained by Laboratory Techniques and Well Logs: Site 462 in the Nauru Basin of the Pacific Ocean

Electrical Resistivity, Sound Velocity, Thermal Conductivity, Density-Porosity, and Temperature, Obtained by Laboratory Techniques and Well Logs: Site 462 in the Nauru Basin of the Pacific Ocean

The effects of alteration and porosity on seismic velocities in oceanic basalts and diabases

The Physical Nature of Young Upper Oceanic Crust on the Mid-Atlantic Ridge, Deep Sea Drilling Project Hole 395A

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