At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

Post-collisional to late orogenic magmatism (570 to 480 Ma) in the Araçuaí-Ribeira Foldbelt is characterizedby the predominance of high-K metaluminous, allanite-sphene-bearing granitoids. Smaller lenses of coroniticgabbro, anorthosite, pyroxenite and phlogopite-peridotite are also common in deeper exposed areas of thisfoldbelt. Several large plutons (³ 100 km2) were mapped by the authors and co-workers in a 1:25,000 scale.In southern Espírito Santo, the deep erosional level associated with a steep topography reveals the internalarchitecture of these intrusions: a tendency to funnel-shaped bodies, with sub-vertical cylindrical roots,grading to shallower angle dipping tops. Associated stocks, sills and dikes of basic and acidic magmasgenerally intrude the enclosing gneisses along the foliation planes, local ductile shear zones and fold axes.The contact to these enclosing rocks is sharp in deeper eroded plutons (Santa Angélica, Venda Nova,Mimoso do Sul and Várzea Alegre). Where higher levels are exposed (Castelo, Pedra Azul and Conceiçãode Muqui), agmatic stoping zones dominate along the borders. The igneous foliation is usually well markedand the schistosity of the surrounding gneisses wrap around the plutons. Each intrusion has a uniquemarble cake (bimodal) internal structure: concentric patterns of more basic to intermediate cores aresurrounded by interfingered lenses of basic to acidic magmatites. Syenomonzonite and granite mark theborders. Widespread evidence of mingling and mixing between contrasting magmas of gabbroic and graniticand/or syenomonzonitic compositions is characteristic for all intrusive complexes. Probably due tolithospheric delamination following collisional orogenesis, the upwelling of hot asthenospheric magmasinduced partial crustal melting. The interaction of these contrasting magmas originated the bimodal plutons.Their emplacement followed older regional paths such as regional fold axes and ductile shear zones.

The Várzea Alegre Intrusive Complex (VAIC) corresponds to a post-collisional (late orogenic) pluton, related to the Brasiliano cycle, situated in the central part of the Espírito Santo State. It intrudes amphibolite to granulite facies metamorphic rocks of the Ribeira Belt. Two distinct domains were recognised in this zoned pluton: an inner domain with opx-gabbro, monzogabbro, diorite, quartz-diorite and megaporphyritic granite, and an outer one comprising an irregular and large ring of charnockitic rocks. Geochemical data from the former reveal medium to high-K calc-alkalic rocks, enriched in incompatible elements, mainly Ba, Sr, La, Ce and Pb and partially depleted in HFS elements. The charnockitic rocks show a high-K alkali-calcic signature; they are rich in Ba, K and some HFS elements, such as Zr, P and Nb. The incompatible element enrichment detected in the rocks of the VAIC has been reported for several intrusions from this part of the Ribeira Belt. A Rb-Sr isochronic age of 508±12 Ma was determined for the megaporphyritic granite. The T DM model age varies from 1.3 Ga (opx-gabbro) to ca. 1.67 Ga (charnockitic rocks), which can be related to an important Mesoproterozoic crustal event. The calculated T CHUR model ages of the cogenetic opx-gabbros and intermediary rocks is ca. 1.0 Ga, interpreted as the time when the basic magma was extracted from the source.

Isolated small bodies of Neoproterozoic coronitic gabbros crop out in the states of Espírito Santo (Jacutinga and Itaoca) and Rio de Janeiro (Amparo), in the central portion of the Araçuaí-Ribeira Mobile Belt. The rocks from Jacutinga and Itaoca are mainly gabbronorites and show a wide range of modal/textural varieties recording crystal-setting processes normally found in layered intrusions. The Amparo intrusion is formed by a coronitic rock, also present as layers in Jacutinga and Itaoca. The primary mineral assemblage consists of olivine, opx, cpx, plagioclase, ilmenite, Ti-magnetite and sulphides. Coronitic overgrowths related to the olivine-plagioclase reaction form concentric rims of opx, amphibole and simplectitic amphibole-spinel around olivine cores. They are all very similar in shape and composition pointing towards similar physical-chemical crystallization conditions. Different geothermometric measurements yielded crystallization temperatures around 800°C, which are close to those calculated for primary opx-cpx pairs (800/940°C). The absence of regional deformational and metamorphic paragenesis is compatible with their intrusion into the middle/ lower crust during a late collisional phase. A long lasting cooling environment at a late magmatic stage induced the sub-solidus reactions. Low K sub-alkaline signatures with clear enrichment in some incompatible elements such as Ba, Sr and LREE associated with high 87 Sr/ 86 Sr initial ratios (around 0.706-0.708) are anomalous chemical characteristics of these gabbros. Enriched mantle types (EM1, EM2 and HIMU) with high Sr-initial ratios are frequently found in the Southern Hemisphere. The chemical anomalies obtained in this study could be related to largescale phenomena, similar to the Dupal anomaly.