Provenance and thermal evolution of rhyolite magma in the Blackfoot volcanic field
The bimodal Blackfoot Volcanic Field (BVF) in eastern Idaho hosts Middle-Late Pleistocene rhyolite domes that are among the youngest topaz rhyolites worldwide. Despite young volcanism in the BVF, its geothermal potential has remained elusive. To evaluate the magmatic and thermal evolution of the fie...
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| Main Authors: | , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
19 October 2025
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| In: |
Journal of volcanology and geothermal research
Year: 2025, Volume: 468, Pages: 1-19 |
| ISSN: | 1872-6097 |
| DOI: | 10.1016/j.jvolgeores.2025.108471 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1016/j.jvolgeores.2025.108471 Verlag, lizenzpflichtig, Volltext: https://www.sciencedirect.com/science/article/pii/S0377027325002070 
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| Author Notes: | Carlos A. Angeles-De La Torre, Axel K. Schmitt, Axel Gerdes, Andreas Hertwig, Michael McCurry, Oscar M. Lovera |
| Summary: | The bimodal Blackfoot Volcanic Field (BVF) in eastern Idaho hosts Middle-Late Pleistocene rhyolite domes that are among the youngest topaz rhyolites worldwide. Despite young volcanism in the BVF, its geothermal potential has remained elusive. To evaluate the magmatic and thermal evolution of the field, we investigated zircon crystals from seven domes by U-Pb and U-Th geochronology as well as correlative trace element and isotopic (δ18O, εHf) analysis. For the three northern domes and the central Sheep Island dome, zircon crystallization occurred between 1006 and 785 ka, indicating younger eruption ages than previously reported. Zircon populations from the three southern domes are on average distinctly younger (mostly 63.4-55.2 ka) and overlap literature 40Ar/39Ar ages. Zircon δ18O averages are overall similar (+4.54, +3.86, and + 4.45 for northern domes, Sheep Island dome, and southern domes, respectively), whereas εHf averages are more variable and strongly negative averaging −13.4, −15.3, and − 10.1 for the corresponding domes. These values indicate higher contributions of Archean crust to the BVF parental magmas and correspondingly lesser degrees of assimilation of low-δ18O rocks compared to coeval rhyolites from the axis of the Eastern Snake River Plain. Cooling and fractionation of a 120 km3 magma reservoir emplaced at 95 ka and 6 km depth successfully reproduces zircon ages, magma temperatures, and combined volumes for the southern domes and a geophysically inferred silicic intrusion. This indicates that temperatures at ∼4 km depth could still exceed 300 °C today, although the absence of geothermal surface manifestations and low temperatures encountered in a nearby exploration well suggests that thermal waters are diluted and diverted in a structurally controlled hydrological system. |
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| Item Description: | Gesehen am 17.04.2026 Online veröffentlicht: 19. Oktober 2025 |
| Physical Description: | Online Resource |
| ISSN: | 1872-6097 |
| DOI: | 10.1016/j.jvolgeores.2025.108471 |