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Deep resistivity geophysics of the San Juan–Silverton caldera complex, San Juan County, Colorado (USA)

April 10, 2024

Magnetotelluric (MT) and audiomagnetotelluric (AMT) data are used to better understand the subsurface geology and mineral resources in the San Juan–Silverton caldera complex located near Silverton, Colorado, western United States, as part of the extensive southern Rocky Mountains volcanic field that covers much of southwestern Colorado and northern New Mexico. Seven MT and AMT profiles of varying lengths image resistivity structure to depths of ~5 km. The AMT inversion models characterize geophysical responses of near-surface lithologies, structures, and mineralized systems and also help corroborate airborne electromagnetic data at shallow levels. The MT inversion models extend our depth of investigation from near the surface to great depths (~5 km) and help to form hypotheses about roots of the hydrothermal plumbing that fed shallower mineralized systems. Subsurface high resistivities occur beneath intermediate-composition lava flows and Proterozoic units. Subsurface moderate- to low-resistivity values may reflect hydrothermal plumbing that served as flow paths for mineralizing fluids and metallic ore formation. The model interpreta­tions presented in this study could be utilized in remediation planning or mineral resource applications. The methods used could be applied to other watersheds with similar volcanic environments containing acid-generating historical mines or hydrothermally altered and mineralized source rocks.

Publication Year 2024
Title Deep resistivity geophysics of the San Juan–Silverton caldera complex, San Juan County, Colorado (USA)
DOI 10.1130/GES02550.1
Authors Brian D. Rodriguez, Douglas Yager, Eric D. Anderson, Robert L. Runkel, Bennett Eugene Hoogenboom, Bruce Smith, Maria Deszcz-Pan
Publication Type Article
Publication Subtype Journal Article
Series Title Geosphere
Index ID 70254134
Record Source USGS Publications Warehouse
USGS Organization Colorado Water Science Center; Crustal Geophysics and Geochemistry Science Center; Geology, Geophysics, and Geochemistry Science Center