Scienc c \ , I/nir.c.r.,ity ofS[r~Xrrtc.he\r,[rn, Str.rXrrtoon, S~~J X ., ('rrnrrtla S7N QWO The effect of pore-water salinity on the elitstic wave velocities and electrical resistivities of frozen. saturated specimens of two sandstones and a limestone have heen s t~~d i e d in the temperature range -15 to +4"C. The specimens were saturated with solutions whose salinities varied from 0.0 M (distilled water) to 1.0 M NaCI.An increase in pore-water salinity reduces the effect of sharp increases in velocity as the temperature is reduced below P C . The ratio of compressional to shear-wave velocities shows a weak dependence on temperature and salinity. Calculations of the ice content showed that the pore spaces were not completely filled with ice, even at the lowest temperature (-15°C) reached.An increase in either temperature or salinity was found to lower the complex I-esistivity, and to extend the range of frequency over which the resistive behavior, rather than the dielectric, was dominant. The decrease in resistivity was observed to be most rapid when the pore water salinity was increased from 0.0-0.3 M. The ratio of the resistivity ofa rock when frozen (p,) to that when thawed (p,) can be shown to he related to the fraction (S,) of the water remaining unfrozen at subzero temperatures by p,/p, = (,S,+.)' ". By combining the results of the velocity and resistivity measur-ements. it was found that 1.1 = 0.9 logpf/pt + 2.3.On a Otudie I'effet de la salinite de I'eau interstitielle sur la vitesse des ondes dl:istiques et sur ia resistivite dlectrique d16chantillons geICs et satures de deux gres et d'un calcaire dans le domaine de temperatures de -15 +4"C. On a sature les echantillons avec des solutions dont la salinite variait de 0.0 M (eau distillee) jusqu'A 1.0 M d e NaCI.Une augmentation de la salinitk de l'eau interstitielle rkduit I'effet des augmentations nbruptes de vitesse lorsque la temperature descend en dessous de 0°C. I,e rapport de la vitessede I'onde de compression ;i celle de I'onde de cisaillement indique une bible dependance avec la temperature et la salinite. Lxs calculs de teneur en glace ont montre que les pores n'etaient pas complktement remplis par la glace meme lorsqu'on atteint la plus faible temperature (-15°C).Une augmentation de la temperature 011 de la salinite diminue la resistivite du complexe et etenct le domnine de frkquence dans lequel le comportement resistif, plutct que dielectrique, dsmine. On a observe yue la diminution la plus rapidede resistivite se produisait lorsque la salinite de l'eau des pores augmentait de 0.0-0.3 M . 1,e rapport de la resistivite de la roche A I'etat gele (p,) ~ la resistivite ii I'ktut degelk (p,) est lie B la fraction (S,) de l'eau non gelee h des temperatures sous zero selon la relation pf/pt = (S,,)'-". En combinant les resuttats des rnesures de vitesse et de resistivite, on a iruuve que: n = 0.9 logpllp, + 2.3. Traduit par le journal]Can.
Elastic wave velocities and the quality factor Q were measured on specimens of Berea Sandstone as their water vapor content was increased by exposure to an environment of increasing relative humidity (RH). At a maximum value of RH (= 0.98), the moisture absorbed was about 0.15% (vs. 9.62% for full saturation) of their dry mass.The bar velocities in the torsional and longitudinal vibrational modes were measured in the frequency range 1–20 kHz, while the pulse first-arrival compressional and shear-wave velocities were obtained at 820 kHz. Over the range of variation in relative humidity from 0.0 (vacuum ~1 Torr) to 0.98 the velocities showed a decrease of 20–30%, the bar velocities undergoing the greater change. Over the same range the Poisson's ratio fell from 0.2 to 0.1.The value of the quality factor Q fell sharply from ~200 to ~50 during the initial increase (about 0.01% by weight) in the moisture content. Further addition of water vapor produced no significant change in Q for either mode. Also, no systematic variation of Q with frequency was observed. However, when the amount of moisture in the specimens increased to about 0.15% by weight, not only did the Q values decrease but also began to show a frequency dependence. This change in the frequency variation of Q suggest that, while the water molecule layers initially absorbed by the specimens form a solid phase, a thickness is reached beyond which they depict bulk water behavior. A rough estimate of this thickness was found to be about 110 Å.On a mesuré la vitesse des ondes élastiques et le facteur de qualité Q sur des spécimens de grès de Berea lorsqu'on augmentait leur teneur en vapeur d'eau par exposition à un milieu d'humidité relative (HR) croissante. Pour la valeur maximale de HR (= 0.98), l'humidité absorbée était d'environ 0.15% (par rapport à 9.62% pour la saturation complète) de la masse à l'état sec.
A physical properties database of rock types from the Trans-Hudson Orogen provides information for interpretation of geophysical surveys over the Trans-Hudson Orogen. Measurements have been made on 320 samples (all reduced to core) representing metamorphosed Archaean and juvenile Proterozoic orogenic rocks. Water saturated densities were generally between 2600 and 3100 kg m3. In most cases, the porosity was < 1%. Except for a few samples, magnetic susceptibility ranged from 20 to 4000 × 106 SI units. P- and S-wave velocities were made under maximum uniaxial stress and triaxial stresses equivalent to depths of ca. 4 km. P- and S-wave velocities measured were 57 km s1 and 34 km s1, respectively. Electrical resistivity measurements were made at room temperature from 5 Hz to 10 kHz after samples were oven dried and after saturation in solutions with salinity between 0.0 and 1.0 mol/L. Increasing salinity caused a reduction in resistivity. The porosityresistivity data is in reasonable overall agreement with Archie's Law for all rock types. A minimum value of 50 Ω m was obtained from samples not containing significant sulphide minerals or graphite. For sulphide and graphite-bearing samples, resistivity was as low as 1 Ω m. The resistivity data are consistent with the hypothesis that North American Central Plains (NACP) conductivity anomaly could be due to the presence of graphite- and (or) sulphide-rich bodies or saline pore fluids in the crust. Thermal conductivity measurements made using a "divided-bar" apparatus yielded values between 1 and 5 W m1 K1.
A B S T R A C TThe primary economic uranium (U) mineralization indicators in the Athabasca Basin are the reactivated prominent basement deformation zones, basement alteration halos, and the overlying sandstone alteration halos enveloping the deposit. High-resolution seismic surveys, from the Shea Creek area, are investigated to assess the potential of the surface seismic reflection technique for detecting these key mineralization markers. Four seismic profiles identify ductile to highly brittle deformation features of the basement. One of the brittle deformation features is a southwest-dipping prominent reactivated shear zone comparable to basement structures hosting other known deposits in the basin. The Carswell meteor impact structure is also a conspicuous component of the Shea Creek regional structural regime. The seismic sections identify several features of the impact structure, including recognition that the dimensions of this structure are significantly larger than those estimated by previous geological studies. This larger area includes both the Cluff Lake mine and the Shea Creek U deposits, and it reveals that the basement was considerably disturbed by the impact and suggests the reactivation of the southwest-dipping shear zone. Complex trace analysis of the seismic sections provides detailed information about the lateral changes in the reflectivity properties of the unconformity interval, which is another key zone of interest for uranium exploration. Based mainly on velocity information, several sub-zones of clay alteration and silicification were identified within prominent fracture depth intervals: both in the sandstone and the basement. Thus, this study documents that these primary mineral indicators can be detected by the seismic method. Cross-plots of velocity versus density of well log data identify changes in lithological units such as unaltered basement, fractured/altered basement, unaltered sandstone, clay alterations in sandstone, and silicification in sandstone.
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