Petrography, mineral chemistry and whole-chemistry studies from the Potrerillos Pluton and comparison with the Cerro La Gloria Pluton: arc and retroarc magmatism in the Early Carboniferous

Los plutones Potrerillos y Cerro La Gloria afloran, respectivamente, en el sur de la sierra de Toro Negro (Sierras Pampeanas occidentales) y en el flanco occidental de la sierra de Famatina. Estudios de química mineral (alrededor de 80 análisis), obtenidos a partir de minerales cristalizados en el plutón Potrerillos, sobre muestras que cuentan con datos de química de roca total presentados en este trabajo, y su comparación con aquellos datos propios informados para el plutón Cerro La Gloria, indican que biotitas y anfíboles cristalizaron en un ambiente de arco y retroarco, respectivamente. Los datos de química de roca total son plenamente consistentes con los estudios de química mineral. Entonces, aunque el plutón Potrerillos está localizado sólo a 45 km al oeste del plutón Cerro La Gloria, y ambos fueron emplazados durante el Carbonífero inferior, el estudio comparado es de singular relevancia, ya que sus magmas parentales fueron generados en dos escenarios geodinámicos diferentes, de arco y retroarco, en cada caso. Esta conclusión es una contribución relevante para entender la evolución del margen preandino del SO de Gondwana durante el Carbonífero inferior.The Potrerillos and Cerro La Gloria plutons crop out in the south of the Sierra de Toro Negro (Western Sierras Pampeanas) and the western flank of the Sierra de Famatina. Studies of mineral chemistry (about 80 analyses) obtained from crystallized minerals in the Potrerillos pluton, on samples with whole-chemistry data presented in this paper, and their comparison with our own data reported for Cerro La Gloria pluton, indicate that biotite and amphibole crystallized in an arc and a retroarc environment, respectively. The whole-chemistry data are fully consistent with the mineral chemistry studies. Thus, although the Potrerillos pluton is located only 45 km to the west of Cerro La Gloria pluton and both were emplaced during the Early Carboniferous, their parent magmas were generated in two different geodynamic settings. This conclusion is an important contribution to understanding the evolution of pre-Andean margin of SW Gondwana during the Early Carboniferous.Fil: Dahlquist, Juan Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; ArgentinaFil: Alasino, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; Argentina. Universidad Nacional de la Rioja; ArgentinaFil: Morales Camera, Matías Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; Argentin

Devonian F-rich peraluminous A-type magmatism in the proto-Andean foreland (Sierras Pampeanas, Argentina): geochemical constraints and petrogenesis from the western-central region of the Achala batholith

A new LA-ICP-MS crystallization age of 370 ± 8 Ma is presented for monzogranite from the Achala batholith, the largest Devonian igneous body in the Sierras Pampeanas, confirming previous U-Pb zircon ages and indicating emplacement within a relatively short episode. Granitic rocks from the central area of the batholith display restricted high SiO2 contents (69.8–74.5 wt.%). Major element plots show ferroan and alkaline-calcic to calc-alkaline compositions with an A-type signature. High concentrations of the high field-strength elements such as Y, Nb, Ga, Ta, U, Th, and flat REE patterns with significant negative Eu anomalies, are also typical of A-type granites. The aluminium saturation index (1.10–1.37) indicates aluminous parent magmas which are further characterised by high FeO/MgO ratios (2.6–3.3) and F contents of igneous biotites (0.9–1.5 wt%), as well as relatively high AlIV (2.39–2.58 a.p.f.u.) in biotites and the occurrence of primary muscovite. Petrogenetic modelling supports a source enriched in plagioclase and progressive fractional crystallization of feldspar. The central area of the batholith displays small-scale bodies composed predominantly of biotite (80 %), muscovite (10 %) and apatite (10 %), yielding rock compositions with 2.3–5.4 wt. % P2O5, and 6–7 wt.% F, together with anomalous contents of U (88–1,866 ppm), Zr (1081–2,581 ppm), Nb (257–1,395 ppm) and ΣREE (1,443–4,492 ppm). Previous studies rule out an origin of these bodies as metasedimentary xenoliths and they have been interpreted as cumulates from the granitic magma. An alternative flow segregation process is discussed here.Fil: Dahlquist, Juan Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Alasino, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; Argentina. Universidad Nacional de la Rioja; ArgentinaFil: Bello, Carina. Comisión Nacional de Energía Atómica; Argentin