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.

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