Fluid inclusion studies of epithermal gold-bearing quartz veins in the La Libertad district, Nicaragua

Abstract

The La Libertad mining district in central Nicaragua, is an epithermal deposit of Au-bearing quartz veins hosted in Tertiary basic to intermediate volcanic rocks. Fluid inclusion studies in quartz from the epithermal veins show that the ore forming solution varies in temperature between 172 and 316°C with a mode around 230-240°C. The salinily of the was in the, range of 0.98-2.10 eq. wt.% NaCl. The original ore solution involved is defined as dominated by meteoric water and sodium chloride (NaCl), as the main component, no CO₂ was detected. The minimum depth of emplacement of the deposit was probably between 370-570 m. This gives an estimated erosion rate of 2.4-4.4 cm/1000 years and an estimated thermal gradient for the district of greater than 150°C/km. Due to the close relationship between the ore forming processes and volcanism in the district, the epithermal deposit at La Libertad appears to be the result of magmatic hydrothermal systems.