Recent Advances in Understanding Gold Deposits: from Orogeny to Alluvium
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Mesozoic Biological Events and Ecosystems in East Asia covers a wide range of topics, encompassing palaeoenvironments, palaeoecosystems and important vertebrate, invertebrate and plant fossils, some found in amber with excellent preservation of delicate morphological features. Fifty-three authors from a number of different disciplines – geochronology, palaeontology, stratigraphy, sedimentology, tectonics and geochemistry – contribute to the 18 articles in the volume.
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Paleoproterozoic gold deposits at Alta Floresta Mineral Province, Brazil: two overprinted mineralizing events?
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Published:January 03, 2023
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CiteCitation
Maria José Mesquita, Márcia Elisa Boscato Gomes, Igor de Camargo Moreira, Renata Augusta Sampaio Paes, Hevelyn Eduarda da Silva Martins, José Henrique Matos, Alberto Ruggiero, Guilherme Primo, Diego Fernando Ducart, Luciano Poggi, Vanessa Pimenta, Leonardo Zanchetta de Laurentis, André Massanobu Ueno Kunifoshita, 2023. "Paleoproterozoic gold deposits at Alta Floresta Mineral Province, Brazil: two overprinted mineralizing events?", Recent Advances in Understanding Gold Deposits: from Orogeny to Alluvium, T. Torvela, J. S. Lambert-Smith, R. J. Chapman
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Abstract
Large gold provinces commonly show complicated mineralization histories, and the Paleoproterozoic Alta Floresta, one of Brazil's most exciting Au–Cu mineral provinces, is a good example. The current models defined four deposit types, all connected to a single (1.88–1.75 Ga) magmatic–hydrothermal event. However, long Province history, diverse geodynamic environment and older ages of Type-1mineralization weaken the single metallogenic event and enable the hypothesis of overprinted mineral events. By scale-integrated analyses, we revise the tectonic–geological context, structural–hydrothermal alterations and chlorite–white mica geothermobarometry and propose the Type-1 as an older, granitoid-hosted orogenic mineralization, with subsequent overprinting by the magmatic–hydrothermal event. The older orogenic gold event developed orogenic gold deposits on WNW-trending shear zones in the Peixoto de Azevedo domain granitic–gneiss rocks. Phengite, biotite and chlorite–carbonate phyllonites (3.3–6.1 kbar, 300–420°C) host fault-fill quartz veins (pyrite–chalcopyrite–magnetite–pyrrhotite–gold–Bi–Ag tellurides). Mg-rich chlorite–phengite is the main alteration footprint for this mineralization type. A younger magmatic–hydrothermal event in the Juruena magmatic-arc rocks produced Fe-rich chlorite–white mica alteration zones (0.6–4.6 kbar, 120–380°C) and disseminated and stockwork–breccia ore (pyrite–chalcopyrite–gold–molybdenite–Ti minerals–allanite) in porphyry–epithermal deposits. Where the younger mineralization overprints the older, phyllic alteration destroyed the phengite orogenic gold phyllonite Sn+1 foliation. The ages of two pyrite populations (1979 and 1841 Ma) in the older fault-fill veins and molybdenite in late fractures (1805–1782 Ma) or disseminated in the c. 1.79 Ga syenogranite porphyry suggest more than two episodes of mineralization. These two events differ in their alteration styles, P–T conditions and structural, mineralogical and textural ore styles. The multiscale approach sheds light on the relationships between the various mineralization events, allowing a new explorational potential within the province.
Supplementary material: Chlorite and white mica complete chemical composition data and other characteristics of the studied deposits are available at https://doi.org/10.6084/m9.figshare.c.6056324
- Brazil
- copper ores
- gold ores
- hydrothermal alteration
- magmatism
- metal ores
- metallogeny
- metasomatism
- mineral composition
- mineral deposits, genesis
- mineralization
- overprinting
- P-T conditions
- Paleoproterozoic
- Precambrian
- Proterozoic
- South America
- structural controls
- upper Precambrian
- Alta Floresta mineral province
- Peixoto de Azevedo Domain