Skip to main content
U.S. flag

An official website of the United States government

Electromagnetic and magnetic imaging of the Stillwater Complex, Montana, USA

May 26, 2023

Modelling and analysis of helicopter electromagnetic data result in resistivity and susceptibility models and derivatives of magnetic data that characterise shallow parts of the Stillwater Complex, critical for aiding exploration and expansion of globally scarce critical and battery mineral resources that include platinum group elements, nickel, copper and chromium. The magnetic susceptibly models derived from the electromagnetic data and the tilt derivative of the magnetic data image layering, mafic dikes, banded iron formation, and serpentinised peridotite. Known areas with contact-type mineralisation are generally characterised by low resistivities and susceptibilities where the volume of mineralised rock is large and/or the depth is shallow. We use iso-cluster and edge detection analysis of both resistivities and susceptibilities to identify potential mineralisation in poorly characterised regions as well as faults. Low resistivity layers beneath large landslides reflect water saturated porous slip surfaces which can interfere with drilling. This uncommon approach of tightly linking the resistivity and susceptibility models and magnetic anomaly data to rock property, surficial geologic, drill hole and soil geochemistry data to image the geology in the upper ∼100 m, aids identification of prospective mineralised regions as well landslides and faults that can impact mineral exploration and local hazards.

Publication Year 2023
Title Electromagnetic and magnetic imaging of the Stillwater Complex, Montana, USA
DOI 10.1080/08123985.2023.2214166
Authors Carol A. Finn, Michael L. Zientek, Benjamin r. Bloss, Heather L. Parks, Justin Modroo
Publication Type Article
Publication Subtype Journal Article
Series Title Exploration Geophysics
Index ID 70246673
Record Source USGS Publications Warehouse
USGS Organization Geology, Geophysics, and Geochemistry Science Center