Potassium-argon dates from the Jemez volcanic field--Implications for tectonic activity in the north-central Rio Grande rift
— Jamie N. Gardner and Fraser E. Goff

The Jemez Mountains volcanic edifice straddles the western margin of the Rio Grande rift which is locally expressed as three basins (Fig. 1). Volcanism in the Jemez Mountains has been intimately related to mid-Miocene through Quaternary tectonic activity of the Rio Grande rift (i.e., tectonic activity following the mid-Miocene volcanic hiatus of Chapin and Seager, 1975). Our work in the volcanic field has shown that tectonic activity has had a major influence on the dominant magmatic processes that were operative during various episodes of the volcanic field's development (e.g., Gardner, 1983, 1984). Hence, information regarding tectonic activity in the north-central rift can be inferred from studies of structures and timing of volcanism, with additional credibility provided by the petrology and petrogenesis of the volcanic products themselves. A discussion of the geochemical evidence for the petrogenetic models we use is beyond the scope of this paper; however, data supporting the petrogenetic models include major- and trace-element, microprobe, and Sr and 0 isotopic analyses (Gardner, 1982, 1983, 1984; Loeffler, 1984). In this paper we outline the geology and petrogenesis of the volcanic field, present new and existing radiometric dates, note variations of volcanism with respect to time, present some important relations of certain fault zones in the area, and summarize these data with emphasis on implications for tectonic activity in the north-central Rio Grande rift.