The Balboa ZTEM Cu-Mo-Au Porphyry Discovery at Cobre Panama

Abstract

This paper describes the ZTEM airborne EM and magnetic results over the porphyry copper-gold camp at Cobre Panama, with a focus on the discovery of the blind Balboa deposit in 2010, the first documented case attributed to the ZTEM system. Balboa is the westernmost of six porphyry copper-gold deposits that make up Cobre Panama and it escaped detection in 40 years of exploration that relied primarily on soil geochemistry, airborne magnetics and drilling. ZTEM was flown in summer 2010 to detect resistivity variations related to hidden porphyry systems in a region of dense jungle, difficult access and thick (20–30 m) conductive saprolite cover. The ZTEM survey detected all the known porphyry systems, including Balboa, based on anomalous conductive response. Our study presents the geophysical survey results at Cobre Panama and is supported by 2D-3D ZTEM and magnetic inversions that appear to validate the survey evidence. 2D synthetic modeling appears to confirm the detectability of the weakly conductive Balboa orebody below 30 m of saprolite cover.