Phillip Hallof earned his status as one of the “fathers of modern geophysics” for his pioneering and innovative work in the field of frequency domain induced polarization (IP), which grew from an obscure research effort into an essential exploration tool. He contributed in many ways to the research and development of geophysical equipment, techniques and interpretation, and also provided technical expertise to the mineral exploration industry through his leadership of McPhar Geophysics Inc. and later Phoenix Geophysics. Another legacy of his 35-year career was aiding the discovery of mineral wealth for the benefit of Canada and the global economy.

Hallof was born in St. Louis, Missouri, and educated at the prestigious Massachusetts Institute of Technology (MIT), where he earned a bachelor’s degree in geology (geophysics option) in 1952. While still a graduate student, he undertook research into the then-novel, variable frequency IP method being developed by Newmont Exploration and demonstrated that it gave measurable responses over certain known sulphide deposits. The technology was further refined and successfully field-tested, resulting in a valuable new tool to help identify buried mineral deposits that were not conductive and which conventional electromagnetic (EM) surveys could not detect. He also created a new and useful mode of displaying multi-spaced IP and resistivity data in the now standard pseudosection format.

After earning his PhD from MIT in 1957, Hallof joined McPhar Geophysics as chief geophysicist in Toronto, and became president (and a Canadian citizen) in 1961. He led the company into the forefront of IP science and also spearheaded a range of innovations in electrical and EM geophysical techniques. Following the sale of McPhar Geophysics to CIL in 1975, Hallof founded Phoenix Geophysics, which achieved notable advances in both Complex Resistivity (Spectral IP) and Magnetotellurics. Both companies designed, manufactured, and marketed geophysical equipment worldwide; they also planned, implemented, and interpreted geophysical surveys.

Hallof used his exceptional communication skills to convince the exploration community of the merits of advanced geophysics, which he strived to make as user-friendly as possible. He was a prolific author of technical papers and case studies based on exploration successes, of which there were a great many around the world. Through his enthusiastic advocacy, IP became a dominant exploration tool used worldwide, notably for porphyry copper deposits, sedimentary exhalative massive sulphide deposits and precious metal deposits associated with minor pyrite, among others.  An advantage of the frequency domain IP method in the early years was that the equipment often could be smaller and lighter than time domain IP equipment, an advantage in mountainous terrain. (The long-running rivalry between these IP methods was brought to an end by the digital age).

In 1986, Hallof shifted to a consulting role with a number of mining companies and also provided guidance in the startup and early growth of Quantec Geoscience. Along with his peers, he helped make Canada the “Geophysical Capital of the World.”