Evolution of a small silicic system: The McCullough Pass Caldera, Clark County, Nevada

The McCullough Pass Caldera is a small caldera in southern Nevada formed by the eruption of the McCullough Pass rhyolites. The McCullough Pass rhyolites erupted as three successive rhyolitic magma batches from 14.12 to 13.98 Ma and produced the McCullough Pass caldera. Each magma batch was chemically zoned by sidewall crystallization prior to erupting. The first magma batch erupted to produce the McCullough Pass tuff and caused collapse of the Jean Lake caldera along a ring fracture identified by the pattern of Jean Lake domes. The second magma batch produced the Ramhead rhyolite and resulted in collapse of the Ramhead caldera. The third magma batch produced dikes, domes and flows of the Capstone rhyolite, which produced a topographic high. The topographic high prohibited Hidden Valley andesite, which erupted from a cinder cone field surrounding the McCullough Pass caldera, from flowing into the caldera. After volcanism had ended, preferential erosion of the McCullough Pass rhyolites produced the present topographic low known as the McCullough Pass caldera.