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This study delves into the intricate magmatic history of the High Lava Plains, revealing key volcanic activity patterns over time. It documents the geologic record, highlighting intermediate composition volcanism from over 19 million years ago, and periods of magmatic hiatus and bimodal volcanism. The role of shallow subduction, delamination, and extreme extension in magmatic processes is emphasized. Key features such as the impact of the Yellowstone hotspot and the unique geology of Coleman Hills, including mafic dikes and rhyolitic deposits, are thoroughly explored.
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Pre- Basin and Range Magmetism Jody Becker Kelsii Dana (Team Awesome)
Background • Geologic record in the High Lava Plains: • >19 Ma- intermediate composition volcanism • 19-17 Ma- magmatic hiatus • 17-14 Ma- bimodal volcanism; Steens, N NV Rift, and CRB basalts, NW B&R rhyolitic activity • 13-11 Ma- volcanism focused to High Lava Plains, W Owyhee Plateau • <10 Ma- High Lava Plains/NW B&R basalt and age-progressive rhyolite eruptions
Pre-Basin and Range Magmatism • Intermediate composition magmatism • Shallow subduction, delamination of slab • Extreme extension, low angle faulting • Magma mixing • Ignimbrite • Shallow-slab subduction • Delaminating subducting plate • Region potentially affected by Yellowstone hotspot
Coleman Hills • 22 Ma Composite Volcano heavily eroded, Miocene dikes, sills, volcaniclastic sed. exposed • Mafic dikes vesicular with glassy margins • Irregular contacts between sills and contact breccia • Dunes in lithic tuff containing ash and reworked lithics • Rhyolitic deposits in shallow water-filled basin, injected with mafic dikes.
