The main purpose of the field trip guide, along the Costeiro Complex:
partial dehydration melting of supracrustal Ubu-series and associated granitic products;
migmatic areas of magma collection, where hydrous melting and enderbitization processes compete with each other.
The Vitória Pluton is the easternmost intrusive body cropping out in this region. This is a multi-stage intrusion of magma under different H2O/CO2-fluid conditions and different stress regimes. In the border zone, an older greenish charnockite, with thick layers of quartz-diorite, is intruded by a pink granite. The intrusive relations can be observed along Outcrops, on the seaside of Vila Velha, Praia da Costa. In the charnockite, clear magmatic features, such as microgranular and micaceous enclave swarms showing different degrees of deformation. Dykes of fine-grained pink granite and pegmatite veins cut the whole sequence.
This region is particularly interesting to observe the dehydration process in the metasedimentary pile. The beach of Ubu, the type locality for the Ubu- series (Paraíba do Sul Complex), is located approximately 15 km north of Iriri city. Here a sequence of migmatitic cordierite-sillimanite-garnet-biotite gneisses (kinzigite) crop out. Several folded and partially boudinaged calc-silicate layers, point towards a heterogeneous, primary sedimentary rock package. At least two migmatization phases can be recognized: a) folded ptigmatic, and b) unfolded leucosomes. The latter is preferentially emplaced along ductile shear zones, where garnet-rich granitic melt intrudes (Figure 8).
In this region, the G2 hypersthene-bearing enderbites (tonalite, granodiorite, granite) crops out. This rock is comprised of oligoclase, K-feldspar, quartz, biotite, garnet, hornblende and hypersthene. Common accessory minerals are apatite, zircon and ore minerals. Calc-silicate layers, similar to those observed in the Ubu series, is a strong field argument supporting the origin of this sequence through dehydration melting of the Ubu series such as in Outcrop 2.
In this quarry a migmatized garnet-biotite gneiss probably part of the Ubu series (Paraíba do Sul Complex) depicts irregular patches of greenish color related to the incomplete formation of enderbite. The metamorphic rocks are intruded by granite and pegmatite veins, from the latest production of granitic melts.
This is an interesting point to observe the development of augen gneiss textures. A garnet-rich gneiss sequence with similar textures to that of the Ubu series (Paraíba do Sul Complex) as in Outcrop 2, but more intensely migmatized, crops out in this point. Thick bands showing feldspar augen are interlayered throughout the sequence. There are larger amounts of garnet-rich G3 granitoids, originated from the partial melting of the gneisses, but this locally formed granitoid is not seen to form large, independent granitic bodies. Some relicts of refractory melanosome are preserved.