April 2023 – Monthly Talk

Speaker: Ken Witherly, President, Condor Consulting Inc.

Title: What Lies Beneath? A Reflection on the Porphyry Copper Exploration Model

Date: Thursday, April 20, 2023

Time: 4:30pm to 5:30pm PDT

Location: Room 111 – 409 Granville Street, Vancouver, BC, V6C 1T2


Electrical methods have been applied to the search for porphyry copper and IOCG deposits since the early 1950s. While there  is a generally accepted model of disseminated sulfides giving rise to a chargeability response, no clear association has been attached to what EM surveys may be responding to. Work in the early 1990s (Nickson 1993) showed the well-developed supergene blankets over a porphyry copper could be conductive; this observation was however, never applied formally to generally accepted porphyry targeting models. The presence of other conductive zones associated with porphyry copper deposits is even less well studied. On the geological side, while there is a vast body of literature describing porphyry copper deposits and how to discover them, in very few cases do these studies even speculate if anomalous concentrations of sulfides could be conductive. On the geophysical side, observations of unexpected conductivity associated with porphyry systems is sometimes noted but these observations typically stop short of suggesting that there could be a more general observation made that a new class of geophysical feature should be defined. The present study is felt to have gathered a sufficient number of case studies which show that a significant number of porphyry copper deposits posse a mineralogical character which can be identified with EM techniques. This thesis can have significant implications as to how porphyry copper are explored for, especially those at depths >500 m, a generally accepted cut-off for IP techniques.

This presentation is based on a similar talk given in AEGC 2019 in Australia. The talk has been updated several times since. The abstract from the 2019 talk can be downloaded below and forms a good summary.



Ken Witherly graduated from UBC (Vancouver Canada) with a BSc in geophysics and physics in 1971. He then spent 27 years with the Utah/BHP Minerals company during which time as Chief Geophysicist, he championed BHP’s programs in airborne geophysics which resulted in the development of the MegaTEM and Falcon technologies. In 1999, Ken helped form a technology-focused service company that specializes in the application of innovative processing and data analysis to help drive the discovery of new mineral deposits. In 2017, he helped establish the Women Geoscientists of Canada, a group dedicated to support early career women in the minerals industry.


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