Caracterización de la alteración hidrotermal del yacimiento epitermal (Ag-Au) Manantial Espejo, Macizo del Deseado, Santa Cruz, Argentina

ECHEVESTE HORACIO; RODRÍGUEZ M. EUGENIA; LÓPEZ LUCIANO

Río Cuarto

Congreso; X Congreso de mineralogía y metalogénesis; 2010

Asociación Mineralógica Argentina

The hydrothermal alteration associated with the mineralization of Manantial Espejo Ag-Au epithermal deposit is characterized by a filic zone within the immediate vein zone, product of fluids with temperatures up to 250ºC and pH near neutral. A broad zone of intermediate argilic alteration is enveloping the vein zone up to 500 m away from the veins, partially controlled by the intrusion of subvolcanic riolitics domes. The presence of potasic illite indicate temperatures slightly over 200ºC and the absence of alunite is indicative of pH higher than 4. The silification affected mainly travertine beds, ash fall tuffs and volcanic and fault breccias, this alteration is clearly observable in the field. The jasperoids would have formed beneath water table about 200m depth, associated with the formation of coloform-costriform quartz textures in the veins related with the latest stage of the hot spring system. A moderated propilitic alteration affects andesites and dacitic ignimbrites, probably due a deuteric origin. Magmatic fluids produced a strong alteration in hidroclastic breccias, with vuggy silica and tourmaline and garnet presence, the last indicative of temperatures over 300ºC.