Geochemical and geochronological insights into Mesoproterozoic bimodal magmatism recorded in basement inliers of the southernmost Dom Feliciano Belt, Uruguay

Abstract

Mesoproterozoic magmatism exposed in basement inliers (Nico P´erez Terrane) of the southern Dom Feliciano Belt (DFB), Uruguay, includes a bimodal association of metaigneous intercalations of the Zanja del Tigre Complex (ZTC) and coeval felsic orthogneisses of the Campanero Complex (CC). New field, petrographic, geochemical, Sm–Nd and Lu–Hf isotopic, and zircon and titanite U–Pb geochronological data constrain the timing, sources, and tectonic setting of this magmatism. Mafic rocks are divided into two groups. Group 1 comprises basalts and alkali basalts with an asthenospheric mantle source. Negative εNd(t) values and Paleoproterozoic to Archean Nd TDM ages suggest a fertilized mantle, possibly inherited from a previous subduction event. Group 2 comprises basalts derived from a shallower lithospheric mantle source. Positive εNd(t) valuesindicate juvenile mantle input, whereas Paleoproterozoic Nd TDM ages reflect a minor contribution from older crust. Felsic magmatism, with an A-type affinity, is divided into Group 3, representing the extrusive felsic counterpart of ZTC, and Group 4, comprising CC orthogneisses with plutonic and subvolcanic protoliths. New U–Pb LA–ICP–MS zircon ages of 1444 ± 15 Ma, 1449 ± 21 Ma, and 1476 ± 6 Ma from the CC orthogneisses demonstrate the occurrence of the Mesoproterozoic magmatic record in basement inliers of the DFB. Suprachondritic εHf(t) in older orthogneisses indicates juvenile crystallization, while subchondritic εHf(t) in the youngest intrusions likely reflects crustal assimilation. Altogether, geochemical, isotopic, and geochronological evidence indicates that Mesoproterozoic magmatism in the DFB basement was derived from heterogeneous sources in an intraplate extensional setting.