Reconciling airborne and ground geophysical outcomes in the Athabasca Basin, Saskatchewan, Canada

Summary

The Athabasca Basin, Saskatchewan Canada is the world’s premier location of high grade uranium deposits. Most occurrences show a close spatial association with graphite shear-fault zones in the basement rocks (overlain by resistive sandstone) and EM techniques have been used for over 30 years to help map these conductive features. While exploration initially focused on shallower parts of the Basin, current exploration is requiring investigation through thicknesses of sandstone well in excess of 500 m depth. With drilling costs typically now approaching CAN$0.5 million per hole in the deeper parts of the Basin, considerable efforts are being expended to define basement targets with as much spatial resolution as possible. Consequently, most companies are employing some form of ground geophysical surveys to try and sharpen the target focus prior to drilling. We have had the opportunity to compare airborne and ground surveys in a number of locations and have found that there can be considerable disagreement between the conductivity models derived from airborne surveys and those produced from ground EM (active and natural field) or DC resistivity surveys. A number of these examples are presented and discussed so as to better understand what are the likely sources of error and how best to manage the risk of multiple but non-conforming outcomes.

Key words::

• Athabasca Basin
• uranium
• EM
• airborne EM
• ground EM