Geochemistry and U–Pb (SHRIMP) geochronology of Grupelli Granite: New constraints on the cessation of felsic magmatism in the Pelotas Batholith, Dom Feliciano Belt

Abstract The Pelotas Batholith forms the eastern portion of the Neoproterozoic Dom Feliciano Belt and records the final stages of the Neoproterozoic Brazilian–Pan-African orogeny. This granite-dominated belt experienced a complex tectonomagmatic evolution, yet constraints on the nature, and especially, the timing of the different magmatic stages are still scarce. This study provides new geochemical and geochronological constraints on the Grupelli Granite, a post-deformational pluton located in the rural district of Quilombo, Pelotas, RS. This granite crops out as a series of sub-kilometric solid bodies along a NE–oriented fault zone, intruding the Pinheiro Machado Complex that dominates the central and southeastern portion of the Pelotas Batholith. The studied granite is widely used as an ornamental rock due to its extremely leucocratic and isotropic appearance. The Grupelli Granite is homogeneous, relatively undeformed, inequigranular and typically medium-to coarse-grained (1–5 mm), with porphyritic and hypidiomorphic textures. Based on modal mineralogy the rock is a monzogranite with 40–50% quartz, 19–25% K-feldspar, and 15% oligoclase, 3–5% biotite, 2–3% magnetite and ilmenite, and accessory chlorite, zircon, apatite, chalcopyrite, and pyrite. Geochemically, the Grupelli Granite is characterized by high SiO2 (74–77 wt%) and K2O (5.08–5.65 wt%) contents combined with low FeOt (1.71–1.93 wt%), MgO and TiO2 (