La Unión Monzogranite: geochronology and significance of the Jurassic arc in the Sula Terrane, Guatemala

  • Francis Emanuel Salguero-Díaz Universidad de San Carlos de Guatemala, Centro Universitario del Norte. Carrera de Geología, Finca Sachamach, km 210, ruta Las Verapaces, Cobán Alta Verapaz, Guatemala.
  • Luigi A. Solari Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, Qro., 76230 Mexico.
  • Osmín J. Vásquez Universidad de San Carlos de Guatemala, Centro Universitario del Norte. Carrera de Geología, Finca Sachamach, km 210, ruta Las Verapaces, Cobán Alta Verapaz, Guatemala.
  • Ricardo Enrique Milián de la Cruz Universidad de San Carlos de Guatemala, Centro Universitario del Norte. Carrera de Geología, Finca Sachamach, km 210, ruta Las Verapaces, Cobán Alta Verapaz, Guatemala.
  • Carlos Ortega-Obregón Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, Qro., 76230 Mexico.
Keywords: La Unión pluton, Las Ovejas Complex, San Diego Phyllite, Guatemala, Geochronology

Abstract

La Unión pluton (LUP) belongs to the metamorphic and igneous Sula Terrane (ST) of Central Guatemala, limited to the north by the Motagua fault (MF) and to the south by the Jocotán-Chamelecón fault system (J-CH-FS). The basement of the ST is characterized by the high-grade metamorphic rocks belonging to the Las Ovejas Complex and the extensive low-grade San Diego phyllite, the latter in tectonic contact with LUP. A combination of field data, petrographic and geochemical analyses as well as geochronologic dating by U-Pb method, allow to classify LUP as a monzogranite with an age of 170 Ma (average of two dated samples), characterized by high-K calcalkaline and peraluminous affinity and with a REE pattern typical of a continental magmatic arc. Some trace-elements behavior and a comparison of similar-age units found elsewhere in eastern, central and southern Mexico, allow to associate its formation to the lithospheric thinning and extension that occurred during the breakup of Pangea and the opening of the Gulf of Mexico.

Published
2022-07-26
Section
Regular Papers