Lithium clay deposits in the McDermitt caldera, Nevada - Oregon: Characteristics and contributions from closed-hydrologic system diagenesis (CHSD) and possible hydrothermal activity

Magmatism around the McDermitt caldera, an early igneous center of the Yellowstone hotspot, began shortly after 17 Ma with emplacement of Steens Basalt, the oldest part of the Columbia River Basalt.Precaldera volcanic rocks became progressively more silicic through time and included both peralkaline and biotite-bearing rhyolites, which are now exposed in the caldera wall.Collapse of the ~40 x 25 km caldera resulted from 16.4 Ma eruption of ~1000 km 3 of the McDermitt Tuff, which is zoned from aphyric, high-SiO 2 , peralkaline rhyolite to abundantly porphyritic, metaluminous icelandite (Fe-rich, tholeiitic dacite-andesite).A resurgent dome formed shortly after collapse probably related to residual icelandite magma.Minor icelandite volcanism continued to 16.1 Ma, when volcanism ceased.