Geological mapping, followed by petrographic and geochemical studies, conducted near Vila Jussara, locality situed south of Canaa dos Carajas, in the Transition Subdomain of the Carajas Province, allowed significant advance in the characterization of Archean granitoids previously embraced in the Xingu Complex. The oldest unit identified in the area is a hornblende-biotite tonalite of Mesoarchean age (~2.93 Ga) named Sao Carlos Tonalite. It is followed stratigraphycally by a Mesoarchean (~2.87 Ga) tonalitic-trondhjemitic-granodioritic association (TTG, Colorado Trondhjemite) and by a Leucogranodiorite of undefined age but distinct from those associated with the Colorado Trondhjemite. Additionally, in the study area, Neoarchean granitoid bodies (ca. 2.74 to 2.73 Ga, tonalites to granites), previously correlated to Planalto Suite and informally designated here as Vila Jussara Granitoids, were also mapped. Mafic dikes are intrusive in the Archean granitoids. The Sao Carlos Tonalite and Colorado Trondhjemite constitute the main goal of this research and, therefore, are discussed in more detail. The Leucogranodiorites and the Vila Jussara Granitoids are characterized in a more succinct way because they are being studied by other researchers. In this case, the aim was to make a preliminary characterization of these granitoids and compare them with the two studied tonalitic units. This was particularly relevant in the case of the Vila Jussara Granitoids because they have tonalitic to granodioritic varieties that could be confused with the rocks of the two tonalitic units. The Sao Carlos Tonalite has a dominant N-S foliation discordant with the E-W regional trend, is composed of amphibole-biotite tonalite, and shows a remarkable recrystallization of plagioclase and quartz. It yielded an age of ~2.93 Ga (Pb-Pb zircon evaporation; Guimaraes in preparation) and is depleted in silica and enriched in TiO2, MgO, Fe2O3t and CaO compared to the Colorado Trondhjemite. The Sao Carlos Tonalite displays relatively low (La/Yb)n and discrete negative Eu anomalies. Its geochemical characteristics are distinct of those of typical Archean TTG suites, and also of the Rio Maria Sanukitoid Suite. On the other hand, the Sao Carlos Tonalite show strong geochemical contrast with the Bom Jardim Trondhjemite and Pedra Branca suite and significant analogies with the amphibole-bearing varieties of the Campina Verde tonalitic complex of the Canaa dos Carajas area in the northern part of the Subtransition Subdomain of the Carajas domain. The Colorado Trondhjemite shows compositional banding and E-W to NW-SE or, locally NS, foliation with strong dips. It is composed of epidote-biotite tonalite/trondhjemite with subordinate granodiorite. Its rocks show intense recrystallization which affected mainly the plagioclase and quartz crystals. Their geochemical characteristics are consistent with those of typical Archean TTG suites. The heavy REE are strongly fractionated [high (La/Yb)n] and some samples show positive Eu anomalies and others absence of Eu anomaly or discrete negative Eu anomalies. An age of ~2.87 Ga (Pb-Pb zircon evaporation) was obtained for this granitoid. The Leucogranodiorite exhibit a dominant E-W foliation and, besides quartz and feldspars, have biotite, epidote and muscovite as main minerals. Most rocks are porphyritic with coarse- or medium-grained phenocrysts or phenoclasts of plagioclase and alkali feldspar in a fine-grained recrystallized matrix. This unit is better exposed immediately to the east of the mapped area, where it is being studied in greater detail. Geochemical data of these rocks indicate its distinct character compared to the granodiorites of the TTG association (Colorado Trondhjemite). The Vila Jussara Granitoids are intrusive in Sao Carlos Tonalite and Colorado Trondhjemite and form E-W elongated bodies in the central part of the study area. Granites (stricto sensu) are dominant in this unit which includes also granodiorites and tonalites. The granites were not included as a goal of our study but the latter rocks were studied because of the relevance of a clear separation between them and the studied Mesoarchean granitoids with the same petrographic classification. Petrographic and geochemical data show that the granodiorite and tonalite associated with Vila Jussara Granitoids are distinct from those found in the Sao Carlos Tonalite and Colorado Trondhjemite. This conclusion was corroborated by several Neoarchean ages obtained in representative granodiorites and tonalites of the Vila Jussara granitoids (2.75 to 2.72 Ga, Pb-Pb zircon evaporation; Guimaraes in preparation). Keywords: Stratigraphic geology – Archean. Carajas Province. Transitional Subdomain. TTG. Granitoid.
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