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Chronology of Silicic Volcanism

Gail Mahood's group is studying silicic volcanism associated with the main phase of Steens and Columbia River flood basalt eruptions between 16.7 and 15.0 Ma. During this period, ca. 3900 km3 of silicic magma erupted from centers dispersed across 25,000 km2 of the Pacific northwest. The largest and oldest silicic centers, High Rock, McDermitt, and Lake Owyhee caldera complexes, lie along a narrow NNE trend at the transition between the craton and accreted oceanic crust, suggesting that silicic magma generation was greatest where mafic magma intruded more-felsic crust. Less voluminous and younger silicic centers track the spread of mafic dikes to the north. The High Rock caldera complex forms the western end of the Snake River Plain–Yellowstone trend of eastward-younging silicic centers.

Publications: 
  • T.R. Benson, G.A. Mahood, and M.Grove, 2017, Geology and 40Ar/39Ar geochronology of the middle Miocene McDermitt volcanic field, Oregon and Nevada: Silicic volcanism associated with propagating flood basalt dikes at initiation of the Yellowstone hotspot, GSA Bulletin, doi:10.1130/B31642.1

  • G.A. Mahood, T.R. Benson, 2017, Using 40 Ar/39 Ar ages of intercalated silicic tuffs to date flood basalts: Precise ages for Steens Basalt Member of the Columbia River Basalt Group, Earth and Planetary Science Letters, doi.org/10.1016/j.epsl.2016.11.038

  • M.A. Coble, G.A. Mahood, 2015, Geology of the High Rock caldera complex, northwest Nevada, and implications for intense rhyolitic volcanism associated with flood basalt magmatism and the initiation of the Snake River Plain–Yellowstone trend. Geosphere, doi:10.1130/GES01162.1

  • T.R. Benson, G.A. Mahood, 2015, Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: silicic volcanism associated with Grande Ronde flood basalt, Journal of Volcanology and Geothermal Research, doi:10.1016/j.jvolgeores.2015.11.011.

  • M.A. Coble, G.A. Mahood, 2012, Initial impingement of the Yellowstone plume located by widespread silicic volcanism contemporaneous with Columbia River flood basalts. GEOLOGY, 40, 655-658, DOI:10.1130/G32692.1.