Airborne radiometric data map alteration of porphyry copper systems in the Elkhorn district, MT

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Abstract

The Elkhorn district in southwestern Montana is known for past production of high-grade base and precious metals from skarn and carbonate replacement deposits. The district also hosts a porphyry Cu-Mo deposit. A radiometric survey flown over the district and surrounds provides maps of surficial concentrations of potassium, thorium, and uranium. Handheld gamma ray spectrometer measurements on altered and unaltered rocks in the district and surrounding region provide a means to ground truth the airborne data. We demonstrate that the airborne and ground-based measurements show similar map patterns. We calculate ratios of the radioelement concentrations and present a potassium enhancement map that combines potassium and ratios of potassium to thorium and uranium. The results highlight the rocks previously mapped as having K-feldspar-biotite and quartz-sericite alteration assemblages in the Elkhorn district and map additional hydrothermal systems in the region, including known alteration in the Radersburg district. The data enhancement techniques can be used as a screening tool for mapping additional porphyry copper systems.

Publication type Conference Paper
Publication Subtype Conference Paper
Title Airborne radiometric data map alteration of porphyry copper systems in the Elkhorn district, MT
Volume 3
Year Published 2025
Language English
Publisher Society for Geology Applied to Mineral Deposits
Contributing office(s) Geology, Geophysics, and Geochemistry Science Center
Description 4 p.
First page 1200
Last page 1203
Conference Title 18th SGA Biennial Meeting
Conference Location Golden, CO
Conference Date August 3-7, 2025
Country United States
State Montana
Other Geospatial Elkhorn district
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