Abstract

Magnetic data are ubiquitous in mineral exploration. They are often inverted under the assumption that the magnetization is purely induced and in the direction of the geomagnetic field. If remanence or self-demagnetization are present, this assumption can lead to erroneous recovered models. Magnetic vector inversion (MVI) allows for a varying direction of magnetization but triples the number of model parameters and increases the non-uniqueness of the inverse problem. Inversion to account for self-demagnetization requires the same number of parameters as traditional methods but introduces additional ambiguity due to non-linearity in the forward modeling. To address these challenges, we introduce a finite-volume based approach within SimPEG that is capable of handling self-demagnetization effects and remanence simultaneously. We then focus on improving methods for inverting magnetic data to recover subsurface distributions of magnetization and high susceptibility separately. We introduce improvements to magnetic vector inversion in Cartesian coordinates to facilitate the recovery of uniformly magnetized and compact targets. We also show that the developed partial differential equation based formulation drastically improves speed and storage requirements for very large scale problems as compared to commonly used integral methods. We illustrate this by inverting data over the Mt. Isa Inlier region in Australia where we recover a model with 41 million parameters in under two hours. To recover distributions of high susceptibility, we introduce an inversion methodology that utilizes sparse regularization with bound constraints. We also introduce a hybrid-parametric sparse inversion approach for targets with more extreme geometries and very high susceptibilities. We apply the hybrid-parametric method to the Osborne deposit in the southern Mt. Isa Inlier region and show that the results compare favorably with drilling.

Bio

John Weis completed a BSc in physics from Santa Clara University in 2017. After that he worked as a staff geophysicist and crew chief at Zonge International where he led crews to acquire geophysical data for a range of survey types, including IP, CSAMT, MT, gravity, and downhole EM. He started as an MSc student in 2021 at the Geophysical Inversion Facility at UBC and successfully defended his thesis in June 2024 titled “A differential equation-based framework for magnetic inversions to address challenges with high susceptibility and remanence”.

Abstract

SimPEG (Simulation and Parameter Estimation in Geophysics) is an open-source python package for geophysical forward modelling and inversion. We demonstrate the utility of SimPEG to improve 3D EM inversion models and advance exploration outcomes using ground electromagnetic (EM) data, collected on the Portuguese side of the Iberian Pyrite Belt. The EM dataset was collected in a mineral concession in close proximity to the giant VMS deposit complexes at Aljustrel and Neves Corvo. The processing and inversion of EM data remains practically difficult due to variable data formats, unit conventions and numerous system parameters required to accurately represent a geophysical survey.  A data processing and inversion workflow, implemented in Geoscience ANALYST software, is outlined, that documents the steps required to achieve efficient and effective inversion modelling and interpretation of this large ground EM dataset. Throughout, the inversion results are compared to a variety of approaches used on this data including, decay analysis, 1D inversion, plate models and established 3D EM inversion programs (UBC-GIF’s H3Dtdinv). The outcome of the 3D modelling has been interpreted to be a very interesting localized conductivity bright spot, in a favourable structural position, at the end of an interpreted thrust ramp. This result is a compelling exploration target made possible because of the 3D inversion. The presentation is an updated version of the talk given at the KEGS symposium in 2023. Since then, new developments have been made, both with SimPEG modelling package and for this exploration target. Drilling that was carried out in the 2023 season is presented and results from that drilling campaign are presented with interesting implications for the interpretation of 3D EM inversions in this setting.

Bio

Scott is Mira’s Global Director of Consulting who brings general expertise in geophysical modelling and inversion, along with extensive borehole, ground, marine, and airborne EM interpretation and processing experience. He has worked in Canada and internationally on oil and gas, uranium, and base metal exploration teams, with a track record of proven discovery.

Recording

Flyer

Abstract

Geophysical exploration provides important information for resource exploration, studies of geohazards, and investigations into how the Earth works. Seismic exploration is the most widely used geophysical technique and is an invaluable tool for oil and gas exploration. However, no single geophysical technique can answer all questions about Earth structure. An alternative method uses low-frequency electromagnetic (EM) signals to image the electrical resistivity of the Earth. This rock property is sensitive to the presence of fluids and a number of economically important minerals. For more than a century, EM techniques have been applied in areas including hydrogeology, mineral exploration, and geothermal energy development. EM methods focused on near-surface exploration utilize signals generated with a transmitter. For deeper exploration it is most efficient to use magnetotellurics (MT) – an EM method that uses natural EM signals to image subsurface structure. In this lecture, I will describe the physics of the MT method and outline its range of applications. This lecture will emphasize (1) how MT is now capable of working in 3-D to develop realistic models of subsurface resistivity (2) how MT is most effective when used in combination with other geophysical methods, and (3) introduce applications of societal relevance including include mineral exploration, volcanology, geothermal exploration, and tectonic studies.

Bio

Professor Martyn Unsworth is a faculty member in the Department of Physics / Earth and Atmospheric Sciences at the University of Alberta. His research focuses on the development of electromagnetic methods in geophysics. Applications in applied geophysics includes studies in mineral exploration, geothermal energy development and imaging permafrost. He has also used magnetotellurics extensively in investigations of plate tectonics, earthquake hazards and volcanoes. He received a BA in Natural Sciences (1986) and a PhD in Marine Geophysics (1991), both from the University of Cambridge. His postdoctoral research at UBC was focussed on the development of inversion methods for controlled source electromagnetic data. After working as a Research Professor at the University of Washington in Seattle, he joined the geophysics group at the University of Alberta in 2000.

* Note: Student registration fees will be refunded following the breakfast. This has been made possible by generous sponsorship from Condor Consulting Inc.

Please register and pay via Paypal at the link below.
Registration will close on Fri, Jan 19 @ 12pm. Space is limited so register early!

Thank you to everyone for their support!
We have reached capacity and the breakfast is now sold out!

Abstract:

Exploring the Earth, Moon and Mars with Modern Geophysical Sensors
Darren Burrows, BSc (Hons), Fleet Space Technologies

Fleet Space Technologies is a leading Australian space exploration company with a mission to connect and explore the Earth, Moon, and Mars. We will begin this discussion by walking through our journey of designing, building, launching and operating Australia’s first commercial LEO nanosatellite constellation and how we are approaching its expansion. By using a combination of satellite communications, our purposefully designed geophysical sensors, and cutting edge software we are helping to accelerate mineral exploration on Earth. Next we move to our closest neighbour, the Moon, where Fleet will be deploying the Seismic Payload for Interplanetary Discovery, Exploration and Research (SPIDER) to collect seismic data from the lunar surface as part of NASA’s Commercial Lunar Payload Services (CLPS) initiative in 2026. The SPIDER design and testing process will be discussed, as well as our ideas on large scale lunar exploration. Lastly, we will share our ideas on how resource exploration will allow humans to build permanent bases on Mars.

About the Speaker:

Darren graduated from the University of the Witwatersrand in Johannesburg, South Africa with a Geophysics (Hons) degree. Initially he worked in deep Gold mines analysing mining induced seismicity, to ensure safe underground mining conditions. He then moved to Platinum exploration in the Bushveld Igneous Complex planning drillholes, logging core and managing exploration data. A large part of his career was spent in airborne geophysics with Fugro / CGG / Xcalibur where he has held various roles focusing on geophysical data processing & interpretation as well as business development. At Fleet Space Technologies he entered the emerging field of ambient noise tomography and applies it to solve mineral exploration problems.

Our 2023 annual general meeting (AGM) will be held:

at 4:30pm on Tuesday, December 12, 2023
at Moose’s Down Under, Basement 830 West Pender St., Vancouver BC. V6C 1J8

The main order of business will be to elect the Directors of the BCGS and review the past year’s activity. Our bylaws allow for between 4 and 7 Directors. The current directors are standing for re-election.

We are inviting interested persons to nominate themselves for election to join the Board of the BCGS. Please indicate your intent to do so by 23h59 on Thursday, December 7, 2023.  All names of prospective candidates will then be included on a revised AGM notice to be emailed out the following business day if any changes are required.

The BCGS directors standing for re-election are:

We would like to remind you there are two classes of voting members in the BCGS:

1. General members. An annual fee of $20. Will be returned as a discount should they choose to enroll in our annual symposium; and
2. Student members. Free membership upon demonstration of enrollment in a post-secondary program at an accredited educational institution.

In order to participate in the vote, we ask that you pay your 2024 member dues online via Paypal on the “Join Us” page (link below). These member dues will provide membership in the BCGS through 2024. Eligible students, as defined above, are entitled to vote. If you are unsure of your current membership status please send us an email (info at bcgsonline.org) and we’d be happy to check for you.

http://www.bcgsonline.org/join-us/

The AGM is open to all members and non-members.