EPIDOTO MAGMÁTICO: IMPLICANCIAS PARA EL ASCENSO Y EMPLAZAMIENTO DE PLUTONES TRONDHJEMÍTICOS. SIERRA CHICA DE CÓRDOBA.

PINOTTI, LUCIO; D'ERAMO, FERNANDO; VEGAS, N.; CONIGLIO, JORGE; DEMARTIS, MANUEL; TUBÍA, J.M.

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 Epidote is frequently found in intermediate composition calk-alkaline granites, emplaced in relatively deep crustal levels. For some authors, magmatic epidotes differ from those with secondary origin because of their pistacite molecule content (Ps= [Fe+3/(Fe+3+Al)]x100). Moreover, textural differences are usually found between them. Magmatic epidotes are of considerable petrogenetic interest because they can be used to estimate the minimum depth of emplacement and to determine qualitatively the ascent velocity of granitic magmas. Epidotes growing around allanite cores and isolated euhedric crystals are found in Calmayo and El Hongo trodhjemitic plutons from the Sierra Chica de Córdoba. Pistacite contents vary between 25 and 31 %mol. Thus, such textural evidences and the pistacite contents support magmatic origin for epidotes in these plutons. According to structural studies in both plutons and the results of a gravity survey in the El Hongo pluton the ascent of magma took place through subvertical and nearly N-S striking feeder channels. The ascent finished when magma reached a buoyant equilibrium at intermediate crustal levels (~12 km). Epidote crystals not re-equilibrated with the trondhjemitic melts suggest fast velocities for the transport of these magmas. Such conditions are in line with magma transport by permitted, fracture propagation mechanisms.