Titre:	Caracterização e evolução metalogenética das mineralizações auríferas nos prospectos Rosa de Maio, Bandeirantes e Maués, província mineral do Tapajós, Sudeste do estado do Amazonas
Auteur(s):	Alves, Pedro Victor Freire de Souza
Orientador(es)::	Botelho, Nilson Francisquini
Assunto::	Cráton amazônico Província mineral tapajós Petrogênese de granitos Orosiriano Depósito aurífero hospedado em granito
Date de publication:	30-déc-2025
Data de defesa::	18-jui-2025
Référence bibliographique:	ALVES, Pedro Victor Freire de Souza. Caracterização e evolução metalogenética das mineralizações auríferas nos prospectos rosa de maio, bandeirantes e maués, província mineral do tapajós, sudeste do estado do amazonas. 2025. 143 f. Tese (Doutorado em Geologia) — Universidade de Brasília, Brasília, 2025.
Abstract:	The Tapajós Mineral Province (TMP) hosts multiple Au(-Cu-Mo) deposits in the southern-central Amazonian Craton (northern Brazil), some recognized as part of porphyry-epithermal systems, associated with either the arc magmatism of the older magmatic sequence (2.0-1.95 Ga) or the post-collisional to early- anorogenic magmatism of the younger magmatic sequence (1.90-1.86 Ga), which includes the Parauari Suite (PAR, 1.89-1.87 Ga). The Rosa de Maio, Bandeirantes, and Maués are gold deposits associated with the PAR, whose magmatic-hydrothermal evolution and Au fertility remain poorly constrained. In this study, we investigate this fertile magmatism and present new lithogeochemistry, mineral chemistry, Mössbauer spectroscopy on biotite, zircon and monazite U-Pb dating, muscovite Ar-Ar dating, as well as Sm-Nd and sulfur isotope data of both the ore and host rocks. Fractional crystallization played a major role in the magmatic evolution of host rocks, differentiating from tonalitic/granodioritic parental magmas to biotite monzo-/syenogranitic and muscovite syeno-/alkali feldspar granitic magmas. Ferric/ferrous iron ratios estimated by Mössbauer spectroscopy on magmatic biotite indicate oxygen fugacity conditions above the NNO buffer. The Bandeirantes intrusion and the Rosa de Maio Granite (RMG) were emplaced at ca. 1907 Ma and 1890 Ma, respectively, in a late- to post-collisional setting, following a period of subduction- controlled arc magmatism. Neodymium isotope data reveal that the sources of the RMG involve contributions from both juvenile material and crustal rocks from the basement. Magmatic sulfide saturation, a potential factor controlling low Cu/Au ratios, may have been a first-order control on the Au fertility of the RMG. Two distinct hydrothermal systems are recognized in the Rosa de Maio deposit: a deeper system and a shallower, near-surface system. The hydrothermal evolution of the deeper system is characterized by a sequence of four alteration types: sodic, potassic, propylitic, and sericitic alteration. Hydrothermal activity initiated with the exsolution of high-temperature, alkaline aqueous fluids during the late stages of magmatic evolution in the apical zones of the RMG. These fluids promoted pervasive Na metasomatism, followed by K metasomatism of the host biotite granite. Propylitic alteration subsequently overprinted previously formed hydrothermal assemblages in proximal zones of the intrusion center, marking the onset of sulfide precipitation (pyrrhotite ± chalcopyrite) from cooler hydrothermal fluids (~370-170 °C). This stage was followed by fissural to pervasive sericitic alteration, characterized by pyrite, quartz, and sericite formed from similarly low-temperature fluids (~325-160 °C). Sericitic alteration zones are marked by abundant sulfide precipitation, including pyrite, chalcopyrite, and galena, as well as minor native bismuth. The shallower hydrothermal system, genetically linked to the deeper one, is characterized by sericitic alteration and silicification, associated with the development of a stockwork system composed of quartz and pyrite-quartz veins in the upper, distal portions of the intrusion center. Gold mineralization shows a strong spatial association with sulfides, predominantly pyrite, and is characterized by low Cu/Au ratios. It occurs in both systems within sericitic alteration zones and sulfide-rich quartz veins, present both as vein infill and disseminated in altered wallrock. Muscovite from a quartz vein in the shallower system yielded a 40Ar/39Ar plateau age of 1808.3 ± 7.1 Ma, interpreted either as the result of isotopic resetting during a younger thermal event or as evidence of a younger mineralizing magmatism not yet identified in the area. Sulfur isotope analyses of pyrite from both systems yielded δ34S values between +0.5 and +1.3‰, consistent with a dominantly magmatic sulfur source. Overall, the deeper system of the Rosa de Maio deposit shares several similarities with Au-rich porphyry-style deposits, whereas the shallower system likely represents a superimposed epithermal mineralization, now largely eroded.
metadata.dc.description.ppg:	Programa de Pós-Graduação em Geologia
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Collection(s) :	Teses, dissertações e produtos pós-doutorado

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