FLUORITA ACCESORIA EN GRANITOS DE ALTO POTASIO: SU APLICACIÓN EN LA PROSPECCIÓN DE MINERALIZACIONES DE W-MoAgAu MAGMÁTICAS-HIDROTERMALES.

CONIGLIO, JORGE; PINOTTI, LUCIO; D'ERAMO, FERNANDO; PETRELLI, HUGO; DEMARTIS, MANUEL; ODDINO, HERNÁN

San Salvador de Jujuy - Jujuy

Congreso; IX Congreso de Mineralogía y Metalogenia - en el marco del XVII Congreso Geológico Argentino; 2008

Asociación Geológica Argentina

ABSTRACT In the high-K, F-rich devonian granites of the sierra de Comechingones, Cordoba, the W, Mo ± Ag ± Au hydrothermal mineralizations are associated with accessory fluorite-bearing plutons, in leucogranites which evolved from rocks with Albite (An 07-05) and biotite contents of ~ 5% (with XFe ~ 0.70), and crystallized close to 830 °C. The formation of accessory fluorite is strongly inhibited in plutons less differentiated (typically monzogranite and exceptionally granodiorite) with oligoclase (An 21-12) and biotite contents > to 8% and XFe <0, 57. In this case, secondary fluorite can be formed, but there are not metalliferous mineralizations, even though the granites show evidence of pervasive greisenization. Fluorite ± epidote ± muscovite, as secondary association, was developed by subsolidus reequilibrium of the granites between 354 and 318 ºC, involving cloritization of Mg-rich biotite and oligoclase. The formation of accessory and secondary fluorite was conditioned by F-OH exchange between biotite and apatite, but it essentially was the relative abundance of biotite which determined the compatible or incomplatible behavior of F in the magma. The main conclusion of this study is that the greatest metallogenetic potential is restricted to the hydrothermal mineralizations related to high-silica, alkali feldspar leucogranites with accessory fluorite, which represent the most evolved products of the high-K magmatism.