Dianne Mitchinson

Research Associate, Mineral Deposit Research Unit - UBC

Dianne Mitchinson, Ph.D., P.Geo., is a research associate with the Mineral Deposit Research Unit at UBC. Dr. Mitchinson’s expertise is in geological and geophysical data integration and interpretation. Prior to joining MDRU, she was a senior consultant at Mira Geoscience where she employed 3D data integration for mineral targeting. Currently at MDRU, she is working on identifying geophysical footprints of porphyry deposits undercover, and is using geophysics to locate favorable rocks for carbon sequestration in British Columbia and Yukon.

Abstract

Targeting Porphyry Deposit Hostrocks using Geophysics in British Columbia’s Central Quesnel Terrane

Demand for copper is growing with global movements to electrify the economy; however, discoveries of mineable copper resources have slowed significantly during the last decade. Future new mineral discoveries are likely to be made in places that have been underexplored or are difficult to access. British Columbia is well known for having geology favourable for porphyry copper-gold deposits. A large number of developed porphyry deposit properties, occurrences and prospects occur in BC; however, some regions are clearly underexplored due to extensive (primarily glacially derived) surficial deposits. One such region that is particularly interesting is an approximately 250 km by 100 km area within the central Quesnel Terrane. Very few porphyry copper-gold occurrences exist within this region, yet hundreds of porphyry occurrences are identified north and south of it; the Mt. Milligan and Mount Polley mines bookend the area.

The Geoscience BC–funded Identification of New Porphyry Potential Undercover project used publicly-available geophysical data to model overburden thickness and identify new porphyry exploration targets undercover. Interpretations of overburden-bedrock contacts from conductivity models combined with groundwater well, exploration drilling and outcrop data provides constraints for a revised overburden thickness model for the central Quesnel Terrane. A suite of magnetic targets were chosen, guided by geophysical patterns characterizing known porphyry deposit hostrocks in the northern and southern Quesnel Terrane. Three-dimensional magnetic and gravity inversion models were completed to estimate magnetic susceptibility and density values for each target. Targets were prioritized based on petrophysical similarities to known Quesnel Terrane porphyry hostrocks, how thick the overburden is above them and additional cultural and geographical factors. The prioritized targets and associated 3D magnetic susceptibility and density models can be used by porphyry explorers in BC to direct exploration and claim staking in this prospective but underexplored region.

Speaking at

Additions to the Geoscience Toolbox

February 1, 2022 @ 9:00 am - 11:00 am PDT