Terraquest typically flies two or three Alpha Spectra crystal packs each consisting of four 256 cu. in. (total of 2032 cu. in.) downward looking crystals and one 256 cu. in. upwards looking crystal, in conjunction with the digital GRS 256/12 channel Gamma Ray Spectrometer by PicoEnvirotec Inc. The system utilizes individual signal processing from each crystal which provides a significant improvement in the instrumentation, data processing and interpretation. The enhanced capabilities over previous systems enables the acquisition of more reliable and high spectral resolutions that, when combined with the improved processing technology, provides new dimensions in the presentation and interpretation of airborne gamma ray surveys.

Features include:

  • Zero dead time and pulse pile up
  • Real time spectra non-linearity corrections
  • Automatic gain control and spectrum stabilization on each PMT / crystal
  • Dual 256/512 multichannel analyzer
  • Distributed acquisition of detector signal with and internal 1024 bit resolution
  • User defined detector volume of up to 18 crystals

Mid West Uranium Roll-Front Case Study

Total-Count-Terraquest Uranium-Terraquest Vertical-Gradient-Terraquest

Total Count                           Uranium                                  Vertical Gradient

The Vertical Magnetic Gradient image shows alternating magnetic horizons within the basement rocks along the western edge of the survey block and relatively quiet magnetic sedimentary rocks to the east; these sediments overlie the basement rocks and have a shallow dip to the northeast. Within the sedimentary suite, the Total Count image shows well defined radioactive horizons as successively higher strata are exposed in a northeasterly direction. The Uranium image further identifies which of these are uraniferous.