Geologia e geocronologia do Complexo Intrusivo de Venda Nova, Orógeno Araçuaí (Espírito Santo, Brasil)

Abstract

The Venda Nova Intrusive Complex is located in the south-central portion of the state of Espírito Santo, in southeastern Brazil. The area displays a typical circumscribed morphology of inverse zoning at the surface, where rocks such as gabbros and diorites are found in the core, while the edges are composed of granites, syenites and monzonites, accompanied by charnockites and norites present in a narrow strip on the south and southwest margins, as well as locally distributed leucogranites. The chemistry of lithologies in both regions shows relative enrichment in Ba, Sr, Zr, and LREE, except for the charnockites and norites. The concordant U-Pb ages obtained were: granite, 673±4 Ma; charnockites, 650±4.5 Ma and 605±5.9 Ma; norite, 559±4.8 Ma; syenites and monzonites, 531±11 Ma and 513±3.8 Ma; olivine-gabbro, 515±2.8 Ma and 506±3.6 Ma; leucogranite, 501±12 Ma; and gabbro-norite (southwestern core), 501±6.5 Ma. Lu-Hf system data indicate negative values for syenite, with ƐHf (t) ranging from -4 to -12, TDM from 1.24 to 1.56 Ga; leucogranite, with ƐHf (t) between -8 and -17, TDM from 1.37 to 1.74 Ga; and olivine-gabbro with ƐHf (t) between -7 and -12, TDM from 1.47 to 1.80 Ga; and positive values for charnockite, with ƐHf (t) ranging from +3 to +9, TDM from 0.87 to 1.10 Ga. These characteristics point to the evolution of mantle and crustal sources through simultaneous magmatic processes such as fractional crystallization, partial melting, contamination, and magma mixing. The main geological and geochronological aspects related to the intrusions of this body suggest that its formation occurred during the pre-syn and especially post-collisional tectonic and magmatic context of the Araçuaí Orogen.