Testing competing caldera models using uranium-lead geochronology; intrusive history of the Questa caldera: Latir volcanic field, New Mexico, USA

A compelling new model for caldera evolution challenges the standard depiction of large-scale volcanism. Here, I test these competing models by establishing the temporal and chemical relationship between ignimbrite and potential cogenetic plutons related to the Questa caldera, Latir volcanic field, New Mexico.;Results from zircon U/Pb geochronology indicate that the majority of intrusive rocks formed after ignimbrite eruption. The Rio Hondo pluton was assembled over a minimum of 500 k.y., and crystallization progressed from the structurally highest levels downward, consistent with top-down incremental assembly of the pluton. Trace-element modeling demonstrates that the plutonic rocks are not the residua of crystal fractionation, and the predicted systematic difference in trace-element chemistries of plutonic and volcanic rocks is not observed. Finally, the data presented here mostly support the new model for caldera evolution and is broadly inconsistent with the standard caldera model.