Revista mexicana de ciencias geológicas
On-line version ISSN 2007-2902
KIRSCHBAUM, Alicia et al. Mining environmental liabilities in Northwest Argentina: mineralogical, geochemical aspects and environmental consequences. Rev. mex. cienc. geol [online]. 2012, vol.29, n.1, pp. 248-264. ISSN 2007-2902.
In northwestern of Argentina, the Puna region reaches 3700 m a.s.l. and is characterized by arid conditions with high temperature fluctuations and strong winds. In the Puna, there are primary sulfides mining exploitations that ceased their activity twenty years ago without a state-of-the-art closureplan. In the abandoned mines, waste rock and tailing impoundments are rich in pyrite and sulfide and are exposed to weathering, which negatively impacts the quality of water, vegetation, soil and air. Herein, we present the results of the study of three abandoned mines from northwest Argentina: La Concordia, La Poma, and Pan de Azúcar. Superficial water, tailing sediments, soils, vegetation and efflorescent salts were sampled and analyzed. They show evidence of advanced Acid Mine Drainageprocess (AMD). Experimental data of analogue rain-water behavior show a fast pH drop, and dissolution of heavy metals, when water and tailing impoundment sediments are mixed. During the dry season, infiltrated water oxidizes the sulfide minerals in the tailings, and efflorescent salts precipitate from the tailings pore water capturing heavy metals, whereas in the raining season, salts are solubilized as well as some metals. The environmental damage will continue if remediation actions are not implemented.
Keywords : environmental geochemistry; abandoned mines; Pb-Ag-Zn system; eflorescent salts; acid-mine drainage; Puna region; Argentina.