Outline of the petrology and geochemistry of the Keres Group lavas and tuffs
— Rachel Ellisor, John A. Wolff, and Jamie N. Gardner

The Keres Group lavas and tuffs are the earliest products of volcanism from the Jemez Mountains volcanic field, ranging in age from 12.4 to 6.2 Ma. Compositions include olivine tholeiite through high-silica rhyolite lavas and tuffs. Isotope data reveal that Keres Group rocks can be assigned to three petrogenetic trends, each of which contains a chemical component similar to ocean island basalts (OIB). Assimilation-fractional crystallization models of trace element and Sr, Nd and Pb isotope ratio data suggest that one of the petrogenetic groups of magmas assimilated mafic lower crust concurrent with differentiation. The second trend can be modeled as having been contaminated by felsic lower crust. The third petrogenetic trend of samples includes the latest products of Keres Group magmatism, with chemical signatures that suggest they were contaminated by the upper crust.