Estudo do strain e das petrotramas em granitos: Mucajaí, Roraima

Abstract

A combination of structural mapping, systematic sampling, petrographic analyses, anisotropy of magnetic susceptibility and strain mechanisms were used in the syeno- to monzogranite that outcrops near the city of Mucajaí (RR, BR) and exhibits EW- to NE-trending magmatic foliation (S0). Structures as mafic enclaves with porphyroclasts of K-feldspar and schlieren-type bands are evidences of mixing process of magmas (mingling). The interaction of magma viscosity, temperature and strain has generated the conditions for the development of the S0 foliation by magmatic flow. During the plutonic emplacement were registered structural features formed in the magmatic viscous-plastic state and others developed in solid state under high temperature conditions during pluton cooling. The petro-fabric analyses show the registration of the S-type magnetic sub-fabric that would have been originated in simple shear product of a sin-kinetic emplacement in a transcurrent context of granite plutons. The plutonic emplacement of two magmatic pulses would occur under syn-kinematic conditions under the influence of a regional stress field. U-Pb data allowed to define the age of occurrence of the tectono-magmatic event studied around 1,959 Ma.