Open this publication in new window or tab >>2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]
This thesis presents an integrated geological study of the Mundonguara Cu-Au deposit, located within the Archean Manica Greenstone Belt of western Mozambique, which forms part of the eastern Zimbabwe Craton. The research combines petrography, lithogeochemistry, U-Pb geochronology, mineralogy, mineral chemistry, and stable isotope analysis (S, C, and Oisotopes) to develop a comprehensive genetic model and contribute to the understanding of metallogenic processes in Archean greenstone terranes.
Fieldwork and geochemical analyses reveal that the Macequece Formation, which hosts the Mundonguara Cu-Au deposit, comprises Al-undepleted peridotitic komatiites, pyroxenitic komatiites, ultramafic cumulates, and intrusive mafic to felsic rocks. These units show evidence of a mantle plume origin and were emplaced in a continental rift setting. U-Pb zircon ages from intrusive and extrusive units constrain the timing of a major magmatic event to 2.94-2.91 Ga, placing the Macequece Formation within the Lower Greenstones of the Bulawayan Supergroup. A major unconformity separates it from the overlying M'Beza-Vengo Formation, recording a temporal gap of ca. 170 Ma and indicating a craton-wide tectonic transition. Additional Neoproterozoic ages (578-846 Ma) reveal overprinting by later tectono-thermal events, including those associated with the Rodinia breakup and the Pan-African orogeny.
Sulfur isotope compositions of sulfides (δ³⁴S: -0.40‰ to +4.02‰) support a dominantly magmatic source, with minor crustal input. Carbon and oxygen isotope ratios in gangue carbonates (δ¹³C: -9.61‰ to -4.32‰; δ¹⁸O: +4.93‰ to +13.05‰) define multiple stages of fluid-rock interaction, from early carbonate alteration of komatiites to later Cu-Au mineralization. These isotope signatures reflect the involvement of hybrid fluids of predominantly magmatic-hydrothermal character and with minor crustal contributions.
Mineral chemistry data further support this model. Chalcopyrite trace element patterns are consistent with medium-temperature hydrothermal systems (e.g., IOCG, skarn), while Ni enrichment indicates interaction with komatiitic host rocks. Pyrite compositions define two groups with contrasting Co/Ni ratio, pointing to mixing between magmatic and metamorphic fluid sources. Sphalerite Fe content yields ore formation temperatures between 280 and 335 °C, consistent with low- to medium-temperature hydrothermal systems and overlapping withorogenic gold deposits.
Altogether, the data supports a hybrid genetic model for the Mundonguara deposit, involving dominantly magmatic-hydrothermal fluids, minor metamorphic contributions, and metal input from both mantle-derived and local ultramafic rocks. The system differs from classical IOCG-and orogenic gold deposits and is best interpreted as an orogenic gold deposit with atypical metal association hosted in komatiitic rocks.
Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2025
Series
Doctoral thesis / Luleå University of Technology, ISSN 1402-1544
National Category
Geology
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-114370 (URN)978-91-8048-875-4 (ISBN)978-91-8048-876-1 (ISBN)
Public defence
2025-10-30, C305, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency
2025-08-202025-08-202025-10-21Bibliographically approved