Epidoto magmático: implicancias en el ascenso y emplazamiento de plutones trondjhemíticos. Sierra Chica de Córdoba

PINOTTI, L., D`ERAMO, F., VEGAS, N., CONIGLIO, J., DEMARTIS, M., TUBIA, J. M.-2008

SAN SALVADOR DE JUJUY

Congreso; CONGRESO GEOLOGICO ARGENTINO; 2008

SEGEMAR

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, thus distinguishing between diapiric and dike injection ascent. 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 in these plutons varies between 25 and 31 %mol. Thus, both textural evidences and pistacite contents support magmatic origin for epidotes in Calmayo and El Hongo plutons. Structural and gravimetric studies developed in magmatic epidote-bearing trondhjemitic plutons from the Sierra Chica de Córdoba suggest a magma ascent through subvertical and nearly N-S striking fractures. The ascent occurred rapidly until they reached a buoyancy equilibrium in intermediate crustal levels (12 km), where magma transport by fracture propagation and stopping were the most plausible emplacement mechanisms. Epidote crystals not reequilibrated with the trondhjemitic melts suggest high magma transport velocity for these magmas.