Geochemical and mineralogical characterization of the Loma de la Plata and Valle Esperanza deposits, Navidad district, Argentina

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Maximiliano Mercado
Florencia Peralta
M. Josefina Pons
Marta Franchini
Agnes Impiccini
Ana Rainoldi


Loma de la Plata and Valle Esperanza  deposits (with 5000 and 2000 t Ag, respectively) host the main Ag and Cu anomalies in the andesitic  autobreccias of the Cañadón Asfalto Formation. The study of the hydrothermal breccias, veins and veinlets from three sections indicates two pre and post mineralization stages (calcite, laumontite, barite, chalcedony) and one mineralizing stage with three main pulses: a) chalcopyrite-galena-sphalerite, b) tennantite-tetrahedrite, bornite and c) polybasite, jalpaite, stromeyerite, mckinstryite and native silver. Weak to moderate hydrothermal alteration of the volcanic host rocks (chlorite, titanite, adularia, calcite, laumontite, celadonite, chalcedony, illite-smectite and smectite) occurs at the contact zones with the  mineralization. In both deposits, mineral assemblages suggest that hydrothermal fluids were neutral to alkaline and a progressive decrease of the sulfur fugacity during the evolution of the hydrothermal system. Metal precipitation could have been triggered by fluid mixing and/or boiling. Based on the mineralogical textural and geochemical features, both are classified as Ag-rich polymetallic deposits. Unlike other deposits of the Navidad district, silver is mainly contained in Ag-Cu sulfides and in native silver.

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Mercado, M., Peralta, F., Pons, M. J., Franchini, M., Impiccini, A., & Rainoldi, A. (2021). Geochemical and mineralogical characterization of the Loma de la Plata and Valle Esperanza deposits, Navidad district, Argentina. Revista De La Asociación Geológica Argentina, 78(4), 512-538. Retrieved from


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