Several Paleoproteroic granitoids and two volcanic sequences were studied in the Vila Riozinho region. This region is located in the eastern area of the Tapajós Gold Province, near the border between the Tapajós and Central Amazonian tectonic provinces in the south-central part of the Amazonian craton. In the southern part of the region, it was identified the Vila Riozinho volcanic sequence composed of basaltic andesite, basaltic trachyandesite, trachyte and rhyolite, with a high-K calc-alkaline to shoshonitic geochemical signature. Pb-Pb zircon dating indicate ages of 2000 + 4 Ma and 1998 + 3 Ma for this sequence. The São Jorge granite pluton is spatially associated with this volcanic sequence. Two granitoids were distinguished in the pluton, the Old São Jorge granite, with Pb-Pb zircon ages of 1981 + 2 Ma and 1983 + 8 Ma, and the Younger São Jorge granite with an age of 1891 + 3 Ma. The Older São Jorge granite, largely dominant in the pluton, is composed of an expanded magmatic series including biotite-amphibole monzodiorite/quartz monzodiorite, amphibole-biotite monzogranite/quartz monzonite, biotite leucomonzogranite/syenogranite and granite porphyry. It has a metaluminous to mildly peraluminous character, and high-K cale-alkaline signature, similar to that of volcanic arc granitoids. The Younger São Jorge granite was initially identified in drill cores obtained in the gold mineralized area of the pluton. In that area, it corresponds to a hornblende-biotite monzogranite, but biotite leucogranites occur in the southern part of the pluton. This granite also has a high-K calc-alkaline signature, but it differs from the Older São Jorge granite in some geochemical and mineralogical aspects and it is comparatively younger. In the northern part of the Vila Riozinho region, it was identified the Moraes Almeida volcanic sequence, the Maloquinha and Jardim do Ouro granites and a granite porphyry distinct from that associated with the Older São Jorge granite. The Moraes Almeida Formation is composed of ignimbrite and rhyolite with subordinate trachyte, with Pb-Pb zircon ages of 1875 + 4 Ma, 1890 + 6 Ma and 1881 + 4 Ma, respectively. The 1880 + 9 Ma old Maloquinha granite is composed of leucosyenogranite and subordinate leucomonzogranite. This granite and the rhyolite and ignimbrite of the Moraes Almeida Formation show affinities with aluminous, A-type series. The strong petrographic and geochemical similarities between these rocks suggest that they are cogenetic. An age of 1880 + 3 Ma, similar to that of the Maloquinha grafite, was obtained for the Jardim do Ouro hornblende-biotite monzogranite. However, preliminary data indicate that it differs from the former, as well as from the Older São Jorge and Younger São Jorge granites, in petrographic and geochemical aspects. Geochemical and mineralogical data allow the distinction of two different types of grafite porphyries. The first one is spatially associated and similar to the Older São Jorge granite. The second occurs along the contact between the Maloquinha granite and the ignimbrite of the Moraes Almeida Formation and is geochemically similar to the Jardim do Ouro granite and trachyte of the Moraes Almeida Formation. The magmatic activity in the Vila Riozinho region is concentrated into two distinct periods, near the end of the Paleoproterozoic. The Vila Riozinho Formation and the Older São Jorge granite formed during the first period between 2010 and 1970 Ma. At the second period, between 1900 and 1870 Ma, the Moraes Almeida Formation, Maloquinha, Younger São Jorge and Jardim do Ouro granites were formed. The high-K calc-alkaline magmatism that was formed during the first period is probably related to subduction processes. Two hypotheses are considered to explain the diversified magmatic activity registered during the second period: (1) the different magmas could result from late tectonic activity related to the subduction processes; (2) these magmas are related to taphrogenetic processes that affected the Amazonian craton at 1.88 Ga and lasted the entire Mesoproterozoic. It implies to admit a crustal source for the magmas originated during the second period. The second hypothesis is assumed as the more plausible at this stage, but the need for additional isotopic information is emphasized.
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