Magmatism and metamorphism at 1.46 Ga in the Burro Mountains, southwestern New Mexico

Abstract

A BSTRACT — The Burro Mountain granite and biotite-hornblende granite in the Burro Mountains make up a large plutonic complex that cuts 1.65 Ga Mazatzal province metamorphic rocks. A foliation in the pluton consists of aligned biotite, is most prominent near the contact with the country rock, and is absent in the interior of the pluton. We interpret this fabric as being generated during magmatic emplacement. The Burro Mountain granite locally cuts the smaller volume biotite hornblende granite. U-Pb zircon dating of four samples of the Burro Mountain granite yielded ages ranging from 1463–1455 Ma. The weighted mean 207 Pb/ 206 Pb date from all of these samples is