Post-Laramide, Eocene magmatic activity in Sierra de Catorce, San Luis Potosí, México
Keywords: post-orogenic magmatism, petrogenesis, U-Pb dating, granitoids, Eocene, Sierra de Catorce, Mexico
AbstractThe Sierra de Catorce is a N-S-trending mountain range located in the northeastern portion of the Mesa Central physiographic province, Mexico. The Sierra lies at the northern end of the Taxco-San Miguel de Allende fault system, which is interpreted as the surface expression of a major crustal discontinuity. A Triassic to upper Cretaceous sedimentary succession, deformed during the Laramide orogeny, crops out in the range. From the structural point of view, the Sierra de Catorce is a double plunging anticlinorium bounded in its western side by a post-Laramide N-S-trending and west dipping normal fault. We report geochronologic and geochemical data for several post-tectonic granitoids cropping out in the range. The intrusive bodies are I-type continental arc granitoids with Eocene instrusion ages (ca. 38 to 45 Ma, U-Pb determined by LA-ICPMS on individual zircon crystals). Epithermal argentiferous ore deposits are spatially associated with the granitoids. The geochemical signature of the granitoids indicates that magmas derived from a metasomatized mantle, and were highly contaminated with crustal materials. Despite the inferred position of the subduction zone during the Eocene (over 600 km westward), an influence of the subducted slab is needed to explain the metasomatization of the mantle wedge and the high-Ba content observed in all the Sierra de Catorce granitoids. Geochemical features of the granitic rocks are consistent with the regional and local geological framework that allowed rapid emplacement of magma pulses in a post-orogenic extensional geodynamic setting. Key words: post-orogenic magmatism, petrogenesis, U-Pb dating, granitoids, Eocene, Sierra de Catorce, Mexico.