Age relationships of igneous rocks in the Do�a Ana Mountains

Abstract

A bstrAct — Igneous rocks in the Doña Ana Mountains encompass ages that range from at least 43.1 to 33.2 Ma. Rocks of the Palm Park formation are ~43 Ma and are intruded by younger Doña Ana Rhyolite at 36 Ma. Rhyolite of nearby Goat Mountain is of similar age but different composition. Regional dikes, likely related to the Summerford Syenite Sill, are ~33 Ma and significantly post-date Doña Ana and Goat Mountain rhyolitic volcanism. These dikes have different compositions compared to the Doña Ana Rhyolite and are emplaced after the formation of the Doña Ana caldera.