Geophysics, petrophysics and field data integration for porphyry delineation in the Canadian Cordillera – Some caveats

This contribution presents an integrated interpretation of airborne geophysical and remote sensing data over the Central Cordillera in British Columbia, Canada. Data comes from the Search II survey, commissioned by the British Columbia Geological Survey in 2016. The study area is part of the Mesozoic volcanic arcs preserved as the Quesnel and Stikane terranes in Western Canada. Sedimentary and volcanic cover as well rugged terrain and difficult access make field mapping in this area quite challenging. The first part of the work consisted on interpreting the geophysical data to determine structures that could have a role on porphyry emplacement, and the extension of these under sedimentary cover, as well as zones of potassic alteration. Subsequent field mapping was focused on obtaining structural information as well as petrophysical and alteration data over exposed faults and intrusives. Field observations did not locate faults with similar strike to the ones interpreted from the airborne data but did find numerous secondary structures with different strikes that are however consistent with the main stress regime for the area. Magnetic susceptibility traverses indicate that not all alteration features create a decrease in magnetic susceptibility. These are important findings for field structural follow-up of airborne data interpretation.