MELANGE OFIOLÍTICA NOS METASSEDIMENTOS ARAXÁ DE ABADIÂNIA (GO) E IMPLICAÇÕES TECTÔNICAS REGIONAIS

Abstract

OPHIOLITIC MELANGE IN THE ABADIÂNIA (GO) ARAXÁ METASEDIMENTS AND ITS REGIONAL TECTONIC IMPLICATIONS. Based on a detailed study of the structural and geological framework of the Abadiânia region (GO). It was possible to characterize an ophilitic melange petrotectonic association. This association consists of a metasedimentaty sequence, commonly referred to as Araxá metasediments, plus serpentinite bodies with podiform chromite lenses, elongated mafic bodies, and banded porphyroclastic gneisses. The contacts between these lithotypes are tectonic, represented by a S 1 mylonitic folitiation. The serpentinite bodies are chemically similar to residual mantle peridotites, while the mafic bodies show geochemical affinities with tholeiitic island-arc basalts. Both are preferentially emplaced in gamet-mica-quartz schits. On a regional scale, both an evaluation of the petrotectonic characteristics of the ophiolitic melange and a lithologic and structural correlation with other areas exposing similar metasedimentary sequence were carried out. This petrotectonic association correlates with strong Bouguer gravimetric anomalies, indicating that it represents subduction trough deposits involved in thrust movements during the Late Proterozoic. In the Abadiania region, important directional displacement surfaces (K 1) are responsible for the Pirineus inflection structure and are also correlated with strong gravimetric anomalies. Thus, the regional structure in this area may represent a tectonic syntaxis originated as a consequence of trapping of small plates or magmatic arcs during the convergence of two large crustal blocks, or as the result of underthrusting of a wedge-shaped continental plate.