La paragénesis hidrotermal portadora de Ag-Pb-Zn-V-Mo-Cu-P en la pegmatita El Criollo, Cerro Blanco (Córdoba).

COLOMBO, FERNANDO; LOCATI, FRANCISCO

Río Cuarto

Congreso; 10º Congreso de Mineralogía y Metalogenia; 2010

Universidad Nacional de Río Cuarto y Asociación Geológica Argentina

An unusual mineral association was found in cavities and cracks in quartz adjacent to massive hematite in a pegmatite at Cerro Blanco, Córdoba province (31°21'22.9"S - 64°39'6.1"W). The primary assemblage consists of primary chalcocite with scarce inclusions (possibly exsolutions) of an unidentified Ag-bearing Cu sulfide; secondary minerals include covellite (as inwards replacement of chalcocite), pseudomalachite, wulfenite, calcian P- and As-bearing mottramite, malachite, azurite, chrysocolla, genthelvite, and clay minerals (one of them being dickite). With the exception of mottramite (and possibly genthelvite, which was not analyzed), EDS spectra of oxidized phases show only the expected elements. Pseudomalachite was stabilized instead of libethenite by a high a(Cu2+)/a(H2PO4)- ratio at a pH ³6. However, a(H+) was not low enough to precipitate cornetite. The presence of V, Pb, Mo, As, Zn, Cu, Ag, Cr, Co and Ni (these last three found as trace constituents in blue genthelvite) in the hydrothermal minerals suggests an input from a source unrelated to the pegmatitic magma.