Ediacaran magmatism in the Dom Feliciano Belt and Nico Pérez Terrane between the Sierra Ballena and Sarandí de Yí shear zones, central Uruguay: Insights based on geochemistry, geochronology, and isotopy

Abstract

Ediacaran granitic magmatism occurs both within the Archean-Paleoproterozoic Nico Pérez Terrane and the metavolcanosedimentary sequences of the Dom Feliciano Belt (DFB). Despite its fundamental role in understanding the geologic evolution of the region, there is scarce geological information available on this magmatism in central-east Uruguay. For this reason, this article presents petrographic, geochemical, geochronological, and isotopic data from several plutons located in the central portion of Uruguay to assess this granitic magmatism involved in the waning stages of the Brasiliano Orogeny. The predominant lithologies are syenogranites and monzogranites, with subordinate quartz-syenite, quartz-monzonite, and quartz-monzodiorite. Their ages place the magmatism between 620 Ma and 590 Ma, similar to what is observed in other segments of the Dom Feliciano Belt. The geochemical data indicate that the magmatism is slightly peraluminous, predominantly ferroan with occasional magnesian granites, and belongs to the alkalic to alkali-calcic series, with only a few calc-alkalic bodies. Two possible magmatic sources are inferred based on trace element contents, referred to as the LBS (low Ba-Sr) source and HBS (high Ba-Sr) source. The LBS source is characterized by negative Eu anomalies, classified as low Ba-Sr granites, having a low Sr/Y ratio (≤30), and presenting lower alkali enrichment. Conversely, the HBS source is characterized by the absence of Eu anomalies, classified as high Ba-Sr granites, with higher Sr/Y ratios (>40) and generally higher alkali enrichment. The geochemical and isotopic data suggest the involvement of deep crustal material with subordinate metasedimentary participation, with a higher metasedimentary contribution in the LBS source. Furthermore, the model ages between 2.08 Ga and 2.83 Ga, along with the inherited zircon crystals, indicate a significant reworking of an Archean-Paleoproterozoic crust for the whole magmatism. The emplacement of this magmatism is restricted to an orogenic setting, particularly classifying as Late Syn-Collisional to Early Post-Collisional peraluminous granites.