Hydrothermal fluid flow evidenced by mineral alteration assemblages and

MARTÍNEZ, J.C., DRISTAS, J.A. Y MASSONNE, H.J.

Viena

Congreso; EGU General Assembly 2011; 2011

Two horizontally widespread alteration zones of the Barker-Villa Cacique area, Tandilia ranges, share common alteration features recognized by petrography, X-ray diffractometry, electron microprobe analysis, bulk-rock geochemical analysis and K-Ar age dating. An asymmetric alteration pattern with development of an argillic clay mineral assemblage is typical at the Tandilia Late-Proterozoic unconformity zone between the migmatitic and meta-igneous basement, mainly of granodioritic composition, and a quartz-rich epiclastic overlying succession. The most  pervasively altered rocks, presented at the unconformity, usually contain Na-bearing K-white micas, Na and K-bearing pyrophyllite, LREE-bearing aluminum phosphate sulphate (APS) minerals of the florencite-type and tourmaline. Transitional zones to unaltered basement rocks are dominated by K-white mica, chlorite and calcite. Ti-oxides also occur in the alteration profiles.