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Geochronology, Geochemistry, and Fluid Characterization of the Late Miocene Buriticá Gold Deposit, Antioquia Department, Colombia

2013; Volume: 108; Issue: 5 Linguagem: Inglês

10.2113/econgeo.108.5.1067

1554-0774

Guillaume Lesage, Jeremy P. Richards, Karlis Muehlenbachs, Terry L. Spell,

Geochemistry and Geologic Mapping

Abstract Buriticá is an intermediate sulfidation epithermal gold deposit located 75 km north of Medellín, Colombia. It is hosted by the late Miocene Buriticá andesite porphyry, a shallow-level pluton dated at 7.41 ± 0.40 Ma (2σ, MSWD = 2.30; 40Ar/39Ar on hornblende), which intrudes volcanic and sedimentary rocks of the Cretaceous Barroso Formation and the Buriticá stock. Gold mineralization is associated with proximal sericite-adularia and distal epidote-dominant propylitic alteration, and is hosted in two different sets of veins striking and dipping ~072°/87°S and ~105°/87°S. Hydrothermal muscovite from altered host rock yielded a weighted average 40Ar/39Ar age of 7.74 ± 0.08 Ma for two samples, which is within error of the age of the Buriticá andesite porphyry. Sulfur isotope, oxygen isotope, and fluid inclusion data indicate that a relatively hot and saline fluid (~310°C, up to ~8 wt % NaCl equiv) of probable magmatic origin was dominant during stage 1 of the vein paragenesis, and mixed with cooler and less saline groundwater during stages 2 and 3. Fluid inclusion assemblages indicate that boiling was likely the main control on gold precipitation, with cooling and dilution during fluid mixing as a possible secondary control.