STRESS AND VOLCANISM IN THE NORTHERN MOGOLLON-DATIL VOLCANIC FIELD, NEW-MEXICO - EFFECTS OF THE POSTLARAMIDE TECTONIC TRANSITION

The change from Laramide shortening to mid-Tertiary extension coincides temporally and spatially with the end of early intermediate-composition volcanism (lower Datil Group) and the beginning of bimodal volcanism (upper Datil Group and younger rocks) in the northern Mogollon-Datil field. Lithospheric stress regimes provided a common link between tectonism and volcanism during Datil time. Tectonic compression during Laramide crustal shortening prevented dike propagation on a regional scale. Diapirism was the only major mechanism available for ascent of early Datil magmas. Tectonic tension began about 36 Ma in west-central New Mexico, allowing widespread dike propagation. Crustal melting caused by widespread intrusion of mafic dikes may have produced the silicic mode of late Datil volcanism. -from Author