Geological Society of London

Paleoproterozoic gold deposits at Alta Floresta Mineral Province, Brazil: two overprinted mineralizing events?

Version 2 2022-06-22, 14:08
Version 1 2022-06-22, 10:16
Posted on 2022-06-22 - 14:08
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 define 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-1 mineralization weaken the single metallogenic event and enable the hypothesis of overprinted mineral events. By using scale-integrated analyses, we revise the tectonic–geological context, structural–hydrothermal alterations and chlorite–white mica geothermobarometer 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, 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 Ferich 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 ca. 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 multi-scale approach enlightens the relationships between the various mineralization events, allowing a new explorational potential within the province.


3 Biotech
3D Printing in Medicine
3D Research
3D-Printed Materials and Systems
AAPG Bulletin
AAPS PharmSciTech
Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg
ABI Technik (German)
Academic Medicine
Academic Pediatrics
Academic Psychiatry
Academic Questions
Academy of Management Discoveries
Academy of Management Journal
Academy of Management Learning and Education
Academy of Management Perspectives
Academy of Management Proceedings
Academy of Management Review
Select your citation style and then place your mouse over the citation text to select it.


need help?