Pre- to post-collisional Ediacaran magmatism in the western portion of the Borborema Province (NE Brazil): Petrogenesis and insights for the crustal evolution during the Brasiliano Orogeny

Abstract

The Central subprovince of the Borborema Province (NE Brazil) is characterized by a voluminous and diversified late-Neoproterozoic magmatism (ca. 640 to 540 Ma) that resulted in plutons with significant correlations among their U-Pb ages, TDM Nd model ages, εNd(t) values, geochemical signatures, and petrology, evidencing the importance of their study to the understanding of the Brasiliano/ Pan-African evolution in the region. The Jardim Mirim Suite (630 Ma) comprises magmatic-epidote bearing calc-alkaline to slightly high-K calc-alkaline tonalitic and granodioritic rocks characterized by εNd(t) values ranging from −3.0 to 0.8 and Mesoproterozoic TDM Nd model ages (1.4 to 1.1 Ga). The Colina do Horto Pluton (594 Ma) is composed of shoshonitic monzodiorites, monzonites, and granites that exhibit, in general, strongly negative εNd(t) values (−18.2 to −16.5) and Paleoproterozoic TDM Nd model ages (1.9 to 2.1 Ga). The Cana Brava (572 Ma) and Poço plutons consist of alkaline ferroan granites composed of Fe-rich mafic minerals and characterized by strongly negative εNd(t) values (−15.3 to −14.8, respectively), Paleoproterozoic TDM Nd model ages (2.0 Ga), and geochemical signatures similar to high Ba-Sr granites. The study of these plutonic bodies indicates three main magmatic events, developed in pre-collisional (probably associated with the closure of a narrow oceanic basin) to post-collisional (associated with lithospheric delamination process) settings. The contrasting features of the studied rocks reflects changes in magmatic sources in the region. Whereas the origin of pre-collisional magmas is associated with the mixing of juvenile Brasiliano source with Cariris Velhos rocks (ca. 1000–870 Tonian crustal rocks from the Borborema Province), post-collisional rocks were generated by underplating-driven partial melting of a mafic to felsic Paleoproterozoic crust.