Petrogenesis of Pleistocene basalts in the Norris-Mammoth corridor, Yellowstone National Park
The tholeiitic basalts of the Norris-Mammoth corridor formed small Hawaiian-style shield volcanoes. A newly identified volcanic vent, called the Panther Creek volcano, within the Swan Lake Flat basalt stratigraphic unit, was primarily Strombolian in its eruption style. This vent is the first recognized cinder cone in Yellowstone National Park; All basaltic units within the Norris-Mammoth corridor, and the Yellowstone Plateau volcanic field, can be differentiated by isotopes and trace element geochemistry. This suggests that independent partial melting events of asthenosphere were responsible for the petrogenesis of the basalts within the Norris-Mammoth corridor. The simplest model to explain the genesis of the youngest basalt unit (the Panther Creek Swan Lake Flat basalt) is the "injection" model. Injections of EMORB-like mantle into the lithosphere were contaminated, or mixed, with older, fractionated basalt; More precise ages, along with accurate Nd and Sr isotopes, show a general isotopic evolution with decreasing age for basalts in the Norris-Mammoth corridor. This suggests that the basalts in the Norris-Mammoth corridor may be recording a new influx of asthenospheric partial melts into the overlying lithosphere. Pooling of multiple basaltic partial melts in the lithosphere may be melting surrounding crust, generating rhyolitic magma that may coalesce to form a batholith-sized magma chamber and produce a new caldera cycle.