Browsing by Author "Weber, Bodo"

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    Petrogenetic characterization of La Vasca alkaline complex and its relationship to the Eastern Mexican Alkaline Province
    (Elsevier Ltd, 2025) Frei, Dirk; Martínez-Salinas, Edgar; Weber, Bodo
    Peralkaline and agpaitic igneous rocks with local eudialyte mineralization have been reported in the La Vasca alkaline complex (LVAC) but no detailed information on its age and relationship to the Eastern Mexican Alkaline Province (EMAP) has been available. We present petrological, geochemical, isotopic, and geochronological data from the LVAC and the surroundings, located in northwestern Coahuila. The main intrusion is composed of ferroan granitoids that are classified by their alumina saturation index into metaluminous and peralkaline. The metaluminous rocks are monzonite and syenite with post-collisional geochemical affinity. Middle Eocene zircon ages of these rocks range between 47.6 ± 0.3 Ma and 45.4 ± 0.3 Ma and are significantly older than other alkaline rocks from the EMAP. The peralkaline rocks are composed of syenite and eudialyte-bearing foid-syenite with intraplate geochemical affinity that probably coevolved with the metaluminous rocks. Both groups show minimal crustal contamination, with affinity to an Ocean Island Basalt mantle source. The LVAC is explained by a similar formation model than other rocks of the EMAP, suggesting its extension into northwestern Coahuila. Furthermore, the eudialyte foid-syenites represent the first occurrence of agpaitic rocks in Mexico
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    The southwesternmost piece of the Grenville Orogen in Laurentia – New U-Pb and Sm-Nd ages, and P-T estimates from the Sierra del Cuervo, Chihuahua, Mexico.
    (Elsevier B.V, 2025) Frei, Dirk; Weber, Bodo; Nayeli Chacón-Olivas C.
    This paper elucidates the origin and tectonic setting of Mesoproterozoic metaigneous rocks of the Sierra de Cuervo, Chihuahua, Mexico, providing new evidence for the southwestern extension of the Grenville Orogeny in North America. Several geochronological approaches were used, including U-Pb zircon dating by LA-ICP-MS and the Sm-Nd isochron technique, using ID-TIMS. Igneous zircon domains reveal crystallization ages for felsic igneous protoliths ranging from ~ 1.38 Ga to ~ 1.33 Ga, with ~ 1.42 b.yr. old inherited zircon. Whole-rock SmNd isotopic data define an isochron at 1.52 ± 0.03 Ga, suggesting crustal growth during the early Mesoproterozoic. The timing of metamorphism is constrained by Sm-Nd leached garnet-whole-rock isochrons and by U-Pb zircon dates between ~ 1.06 and ~ 1.05 Ga. Metamorphic pressure and temperature conditions were estimated from a metamafic rock sample at 6.4 ± 1 kbar and 520 ± 20 ◦C using conventional geothermobarometry and pseudosection modeling. The results contextualize the Precambrian rocks of the Sierra del Cuervo with metamorphic rocks of the West Texas Uplift thrust over the Laurentian margin. We propose that this thrust represents a remnant of the unexposed Grenville Front and that the Chihuahua and West Texas metamorphic basement is characterized by contemporaneous magmatism and reworked from the Granite-Rhyolite Province of the North American midcontinent during the Grenville Orogeny, comparable to the low-medium pressure allochthonous Ottawan metamorphic belt of the Grenville Province in Canada