Geology and geochronology of Paso del Dragón Complex (northeastern Uruguay): Implications on the evolution of the Dom Feliciano Belt (Western Gondwana)

Abstract

New geologic and geochronologic data of Paso del Dragón Complex (PDC) located at Northeastern Uruguay is analyzed. Two lithodemic units are described and characterized, La Micaela Schists and Cerro La Tuna Serpentinites. La Micaela Schists represent 80% of PDC and it comprises a meta-volcano-sedimentary succession poly-deformed, composed by muscovite-quartz-feldspathic schists, quartzites, and felsic meta-volcanic rocks. Cerro La Tuna Serpentinites represents 20% of PDC and it comprises mafic-ultramafic rocks, also deformed and metamorphosed, composed by serpentinites, varied magnesian schists, hosted by La Micaela Schists. The complex is hosted to the north and west by the Granitic belt of the Dom Feliciano Belt that includes poly-intrusive plutons known from south to north as Aiguá, Cuchilla Dionisio and Sierra de los Ríos batholiths classified as high-K calc-alkaline pre-to post-collisional granitoids. Relevant U–Pb LA-ICP-MS analyses of metamorphic/detrital zircon grains from migmatitic-gneissic basement suggest an age of ca. 668 Ma for the metamorphic event associated with the migmatization process. The deposition and metamorphism age for La Micaela Schists lithodeme are ca. 590 Ma and 570 Ma respectively. The Complex is interpreted as remains of sedimentary and magmatic units generated in an arc-related environment tectonically emplaced within the granites. Their generation, deformation and metamorphism, mainly of Ediacaran age, are associated to the Western Gondwana assembly. This thrust sheet could be regarded as a dismembered ophiolite as previously suggested by other authors. Finally, it is proposed the correlation between Cerro Olivo Complex of Punta del Este Terrane and the migmatitic-gneissic basement of Paso del Dragón Complex based on their similar zircon U-Pb age patterns. Also, it is suggested that Cerro Olivo Complex of Punta del Este Terrane and the Granitic belt might be the main detrital sources for La Micaela Schist.