STRUCTURAL EVOLUTION OF XOLAPA COMPLEX IN THE AYUTLA-CRUZ GRANDE SECTOR, SOUTHERN MEXICO

The Xolapa Complex in the Ayutla-Cruz Grande sector is made up orthogneisses, migmatites, and granites with penetrative deformation of low metamorphic grade, that were intruded for granitic bodies without deformation.

Structural analysis allowed the determination of structural characteristics of each unit and the proposal at least three phases of ductile deformation that affected the Xolapa Complex’s rocks. D1) produced folding, penetrative S1 foliation, L1 stretching lineation, and amphibolite metamorphic facies, mainly affected the orthogneisses. D2) migmatization that generated leucosomes, which are generally parallel to S1. Finally, D3) generated a penetrative foliation S2 with banded pattern in a granitic body that intruded the orthogneises and migmatites.

Petrographic analyses show a contemporaneous deformation-migmatization relationship. Also, U-Pb geochronology carried out on zircons extracted from the migmatitic leucosomes and granitic rocks, suggest the migmatization age, as well as the age of two critical episodes of magmatism that occur after such migmatization in this area.