Abstract

FRIGERIO, Paula Verónica; CINGOLANI, Carlos A  and  CHEMALE, Farid. The Potrerillos granite of the precordillera of Jagüe, La Rioja: Petrological, geochemical and geochronological characterization. Ser. correl. geol. [online]. 2012, vol.28, n.2, pp.107-138. ISSN 1666-9479.

The Potrerillos Granite crops out in a complex tectonic area related with different geological provinces, in the northern Precordillera. The pluton intrudes Ordovician metasedimentary sequence near the tectonic boundary with the Western Pampean Ranges mesoproterozoic basement. To the southwest, it is affected by the 'Jagüé shear belt'. The pluton is composed by monzonites and granodiorites and subordinated granites, alkaline-granites, tonalites, diorites, sienodiorites and gabbros. It is a shallow I-type granitoid, calc-alkaline with some alkaline tendency, showing peraluminous to metaaluminous and potassium-rich geochemical characteristics. In the REE diagram the samples record absence of a Eu anomaly. The slightly positive values of eNd indicate a derivation from a less evolved crust. The petrologic and geochemical signatures are consistent with a subduction-related volcanic arc tectonic setting in an active continental margin. U-Pb zircon ages obtained for three samples place the main magmatism in the Early Carboniferous. One of the analyzed samples has crystals with discordant nuclei with older age, which may correspond to crystals formed early and reabsorbed before joining the main magmatic pulse by assimilation and/or mingling. This Granite was considered within the Gondwanic magmatic cycle of the Frontal Cordillera; however the isotopic data and its deformation show that the main magmatic activity was developed before the Rio Blanco and San Rafael tectonic phases. Considering the field relationships, geochemical signature and composition, it can also be assigned to the set of late to postectonic granitoids developed during the Famatinian orogeny (Chanic phase).

Keywords : Carboniferous magmatism; Chanica Phase; Mingling.

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