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Title

Insights into the genesis of the epithermal Au-Ag mineralization at Rio Blanco in the Cordillera Occidental of southwestern Ecuador: Constraints from U-Pb and Ar/Ar geochronology
Authors
Bineli Betsi, Thierry
Ponce, Miguel
Chiaradia, Massimo
Ulianov, Alexey
Camacho, Alfredo
Published in Journal of South American Earth Sciences. 2017, vol. 80, p. 353-374
Abstract The genesis of the Au-Ag mineralization at Rio Blanco in the Cordillera Occidental (Western Cordillera) of southwest of Ecuador is here constrained. This was done by investigating the temporal and by inference the genetic relationship between the Au-Ag mineralization and the spatially associated magmatic host rocks using zircon U-Pb [chemical abrasion (CA) IDTIMS and laser ablation (LA) ICPMS] and adularia 40Ar/39Ar geochronology. Whereas volcanics hosting the Au-Au mineralization range in age from 37.35 ± 0.30 to 33.09 ± 0.20 Ma (Late Eocene-Early Oligocene), the spatially associated intrusions are of at least two discontinuous phases of magmatism and these include: (i) Late Eocene intrusions that range in age from 35.77 ± 0.19 to 36.03 ± 0.19 Ma, and; (ii) Miocene intrusions of 15.58 ± 0.04 Ma. The 40Ar/39Ar age of adularia from a Bonanza Au (334 g/t)-Ag (2060 g/t)-bearing epithermal vein is bracketed between 14.3 and 14.9 Ma. The temporal relationship between adularia and by inference mineralization and the spatially asso- ciated rocks therefore rules out any temporal link between the Late Eocene-Early Oligocene Rio Blanco Formation, but rather favors a possible genetic relationship between the Rio Blanco Au-Ag mineralization and the Miocene intrusions. The determined Rio Blanco Au-Ag mineralization age is consistent with the established Oligocene-Miocene period of ore deposits in Ecuador and coincides with the extensional tectonic event, which developed intramontane basins in southern Ecuador.
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Article (Published version) (8.3 MB) - document accessible for UNIGE members only Limited access to UNIGE
Other version: http://linkinghub.elsevier.com/retrieve/pii/S0895981117301013
Structures
Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre
Research groups Isotope Geochemistry, Geochronology and Thermochronology
Mineral Resources and Geofluids
Citation
(ISO format) 		BINELI BETSI, Thierry et al. Insights into the genesis of the epithermal Au-Ag mineralization at Rio Blanco in the Cordillera Occidental of southwestern Ecuador: Constraints from U-Pb and Ar/Ar geochronology. In: Journal of South American Earth Sciences, 2017, vol. 80, p. 353-374. https://archive-ouverte.unige.ch/unige:97743

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Deposited on : 2017-10-18

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