Análise estrutural do Eclogito Três Vendas e rochas associadas

Abstract

The Eclogito Três Vendas is the first example of Tonian eclogite related to the Brasiliano Cycle to be found in southern Brazil. The objective of this work is to describe the geometry, kinematics, and structural relationships between the eclogitic outcrops and associated rocks in the study area. The methods employed are the analysis of structural lineaments (at a scale of 1:25,000), geological-structural mapping, and petrography (microtectonics). The lineaments in the study area have NW-SE and NE-SW trends, being associated with the Ibaré and Cerro Branco shear zones, respectively. The planar structures of the studied rocks have two N-S trends in the older rocks and W-E in the younger ones. Veins were found where retrometamorphism is more incident and a destral kinematic indicator posterior to the retrometamorphic thermal peak. The trends of the structures at more than one scale being divided into two groups indicate the contrast of the direction of resolution of the stresses during the deformational history of these rocks. The retrometamorphic veins open the precedent for metamorphic re-equilibration reactions to be at least partly controlled by brittle structures, possibly catalyzed by fluid percolation. The concordant structures observed in the enclosing TTGs and the thermal peak characteristic suggest that the destral deformation occurred concomitantly with the emplacement of eclogite fragments as enclaves immersed in the intrusive rocks of the Imbicuí Complex, in a magmatic arc environment.