Abstract
The La Libertad region is situated in the central part of Nicaragua, within a broad discontinuous belt of Tertiary volcanic rocks that contains several epithermal gold and silver deposits and extends from Guatemala (and Mexico) to Costa Rica.
A chemical comparision between altered and unaltered basic lavas of this area shows that chemical changes associated with the geothermal field type of alteration centered at the mining district reach more than 5 km away from it. Water content, CO2, K and S have beeen added, titanium seem to have been inmobile and Cl partily lost from the fossil geothermal system. Gold, originally concentrated in the glass of basic lavas, was leached during zeolite facies conditions and precipitated with silica in fractures, forming veins on the center of the geothermal field. An estimate shows that the amount of Au released during the alteration was sufficient to give origin to La Libertad deposit.