NON-DESTRUCTIVE CORE LOGGING SYSTEMS

Non-destructive core logging was a major topic of the meeting, being addressed both in curatorial-facility presentations and as separate reports. Major core repositories, especially in those with active drilling and coring programs (and commensurate funding) are increasingly employing non-destructive core-logging techniques. Systems include x-ray and color imaging, x-ray fluorescence and multisensor logging. Repository representatives provided overviews of their systems and discussed the problem of generating and placing vast amounts of actually or potentially inconsistent data in databases.

OVERVIEWS

Walter Hale (ODP Bremen) presented an overview of the x-ray fluorescence system in use at the University of Bremen. Dave Gunn (BOSCOR), Bobbi Conard and Nick Pisias (OSU), and Bill Mills (ODP) provided details of their respective ship and/or shore multisensor operations. Steve Carey (URI) and Brian Edwards (USGS) commented on their x-ray imaging/scanning systems.

MULTISENSOR LOGGING AND CORE IMAGING

The multisensor logging tools are attracting particular attention as many types of data (electrical resistivity, magnetic susceptibility, p-wave velocities, p-wave amplitudes, gamma ray attenuation porosity (bulk density), x-ray tomography, x-ray fluorescence, microwave (water-content) determinations, color-reflectance scanning, core-diameter measurements) may be efficiently logged with little or no disruption of the core surface. Both whole cores, "in the round," and split cores may be logged, and new sensors are being developed.

Various studies comparing the results of traditional analytical procedures against core-log interpretations demonstrated that the logs may serve as "proxies" for more time- and core-consuming analyses. Some examples are,

• The Split Core Analysis Track (SCAT), developed by Alan Mix and others at Oregon State, measures diffuse reflectance spectra. It offers high-resolution shape analyses and, owing to unique absorptional properties of mineral grains also indicates mineral composition. Color variation, thus component variation, has proven to be a very powerful correlation tool. Some examples from ODP coring include Leg 138, where hole to hole correlation was possible on the basis of carbonate content, Leg 154 where Neogene climatic variability was traced on the basis of core mineralogy, Leg 167, on the California margin where color reflectance served as a proxy for organic carbon.
  
  
• Ursula Roehl (University of Bremen) compared Leg 165 shipboard carbonate measurements against those obtained from the XRF core scanner. She found that the data were not significantly different, although the shipboard measurements required samples to be removed from the core, whereas the XRF scanner does not penetrate below the core surface.

GUNN EMPHASIZED THE NEED FOR DEVELOPING STANDARDS in logging-data collection and presentation. He noted that at present huge volumes of data are being generated from different systems, with different calibration procedures and data-processing techniques. Standards are needed now to ensure data is relative, comparable, and compatible. Gunn also demonstrated changes (especially color and water content) as cores aged; core color changes quite quickly. Ideally, only fresh cores are logged, but standards and calibration procedures are also needed to extend logging techniques to older cores.

Atomic-particle rays are hazardous. Users discussed safety apparatuses and precautions taken.

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