Resumen

MYKIETIUK, K.; FERNANDEZ, R.  y  AZEVEDO, F.. Superposed hydrothermal alterations: Result of neutral and acidic pH fluids in Cerro Guananco, DeseadoMassif, Santa Cruz. Rev. Asoc. Geol. Argent. [online]. 2005, vol.60, n.1, pp. 023-031. ISSN 1851-8249.

Epithermal precious metal mineralization is well developed in the Cerro Guanaco area, Deseado Massif. Two different suites of alteration have been recognized, one product of neutral fluids and the other of acid fluids. The neutral suite is characterized by the presence of argillic and propillitic alteration; while the acid suite is formed by advanced argillic alteration with diaspore, pyrophyllite, dickite, illite, illite-montmorillonite and quartz. Coupled with the evidence for the relatively shallow level of erosion in the area, and the alteration body of these zones of advanced argillic alteration, there is a relationship to steam-heated fluids descending fractures below a perched water table.

Palabras llave : Steam-heated waters; Argillic; Propillitic; Advanced argillic alteration.