Abstract

VELASQUEZ RUIZ, Felipe et al. Modeling of the large Miocene epithermal and porphyry gold deposits of the Cauca Metallogenic Belt of Colombia using Monte Carlo simulations. Earth Sci. Res. J. [online]. 2021, vol.25, n.4, pp.415-421.  Epub Mar 16, 2022. ISSN 1794-6190.  https://doi.org/10.15446/esri.v25n4.95289.

The Cauca Metallogenic Belt (CMB) is an inter-Andean area located along the Cauca-Romeral fault zone of Colombia. The CMB comprises a group of twelve Late Miocene magmatic-hydrothermal Au-Ag-Cu mineral deposits positioned between the Western and Central Cordillera of Colombia. In addition to being a widely developed region in exploration and exploitation with known Au endowments of over 1,700 tons, this area represents an exceptional metallogenetic laboratory for modeling an archetype Andean mineralization from a calc-alkaline source with high Sr/Y ratios. Efficiency processes such as ion and halogen transport, oxygen fugacity, and sulfur content have been extensively studied in magmatic-hydrothermal deposits with a geochemical approach. However, the quantification and modeling of these efficiency processes are currently debated. Through multiple iterations using Monte Carlo simulations (N > 2 million), the authors modeled those reservoirs corresponding to the CMB's upper crust. In this way, a high flux of dacitic magma of 0.007 km3/year and efficiencies of 1-2% showed that gold endowments bear heavily with magmatic and hydrothermal Au deposits of the CMB. Outcomes including Au endowments up to 1,000 tons can be obtained for reservoirs below 400 km3 of hydrous melt in brief mineralization intervals between 40 to 120 ka, whereas volumes of400 to 800 km3 are obtained in a 120 to 200 ka range. In contrast, the hypothetical reservoirs for the lower and middle crust of the CMB, through a basaltic calc-alkaline magma flux between 0.0007 and 0.0011 km3/year, the efficiency of ~0.7%, and pressures below 5 kbar, showed sufficient available content of exsolvable H2O and gold to feed the reservoirs in the upper crust of the CMB or to generate gold deposits from them, but in longer time intervals (>1 Ma).

Keywords : Modeling; Monte Carlo simulations; Northern Andes; Miocene magmatism; Cauca Metallogenic Belt.

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