Thermal evolution model for the Pringles Metamorphic Complex, Sierra de San Luis, Argentina

DELPINO, S.; GRASEMANN, B.; BJERG, E.; MOGESSIE, A.

San Juan

Congreso; 15º Reunión de Tectónica; 2012

Comisión de Tectónica AGA (COMTEC)-Universidad de San Juan

The Famatinian Orogenic Cycle is a major igneous and tectono-metamorphic event developed in the southwestern margin of Gondwana during Early to Middle Paleozoic times. The Pringles Metamorphic Complex represents the best exposure of this cycle in the Sierra de San Luis, and constitutes a key area to understand the development of this significant pre-Andean cycle. The present model consider the thermal behavior of the crust in the context of a back-arc basin evolution. This basin develops to the east of a continental magmatic arc (best represented in the Valle Fértil-La Huerta range), associated to subduction initiated at the western margin of Gondwana after the Pampean Orogeny (Neoproterozoic-Early Cambrian). We modeled the pressure?temperature evolution of the crust considering two continuous stages: 1) A first one characterized by extension with concomitant crustal thinning and isotherm increase, which ends with the intrusion of the mafic-ultramafic bodies and the La Escalerilla granitoid and; 2) A compressional stage with associated moderate thickening of the crust and isotherm relaxation. Model parameters were constrained by the available petrological, geochemical, structural and geochronological data. We solved the 1D-Model III heat flow equation for thermal conduction proposed by Spear (1995), which considers exponential distribution of heat producing elements with depth. Solution of the equation was obtained by the finite differences method using the Matlab code ode45 based on an explicit Runge-Kutta (4,5) formula. The model satisfactorily reproduce the P-T conditions established for the rocks through phase relations analysis and geothermobarometry, which vary in accordance with its spatial location at the present level of exposure.