Provenance and thermal evolution of rhyolite magma reservoirs in the Great Basin – Snake River Plain igneous province (USA)

• Applicant: Professor Dr. Mario Trieloff, since 1/2023
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429859409

The Great Basin and the adjacent Snake River Plain in the western USA hosts some one of the world’s best exposed and investigated intracontinental magma systems. This igneous province is characterized by dominantly bimodal volcanism which has been active since the mid Tertiary and continues into the Holocene. The origin of evolved magma in this province has remained elusive, with competing end-member hypotheses comprising fractional crystallization of basalt, mid-crustal magma hybridization, and recycling of preexisting silicic rocks at shallow crustal levels. Because of its accessibility and youthfulness, the Great Basin - Snake River Plain is an ideally suited natural laboratory to investigate the processes of rhyolite generation. Microanalysis of zircon coupled with modeling of the thermal and compositional evolution of zircon-crystallizing magmas is a new and promising approach for constraining the duration and thermal history of silicic magmatism and for re-assessing heat and mass balance in near-surface storage reservoirs of evolved magmas. The focus of this project is on five Pleistocene-Holocene volcanic complexes in the Great Basin - Snake River Plain for which we aim to (1) determine eruption and crystallization ages, (2) elucidate rhyolite magmagenesis, and (3) reconstruct the assembly and cooling history of pre-eruptive rhyolite magma reservoirs. Eruption ages will be determined through 40Ar/39Ar geochronology of sanidine, whereas U-Th disequilibrium and U-Pb zircon dating will yield ages of magmatic crystallization. High spatial resolution isotope and trace element analysis of zircon using secondary ionization mass spectrometry (SIMS) and laser ablation mass spectrometry with inductively coupled plasma (LA ICP MS) will provide the input parameters for a thermochemical model which allows to match zircon age spectra to parameters of magma recharge rate and overall magma volume in open magma systems. This novel approach permits a better understanding of magma storage conditions in near-surface magma reservoirs of the Great Basin - Snake River Plain region. The expected results can contribute to improved prospection for magma-driven geothermal reservoirs in the western USA and other volcanically active regions.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partners: Dr. Oscar Lovera; Professor Dr. Michael McCurry, Ph.D.
• Ehemaliger Antragsteller: Professor Dr. Axel Karl Schmitt, Ph.D., until 12/2022