Analysis of the Brasiliano Oregeny (Deformation Event) Impacts on the Carbonate Rocks Resistance

ABSTRACT: This study explores the effects of the Brasiliano deformational event on the classification and geomechanical behavior of carbonates from the Bambuí Group, specifically focusing on two calcilutite facies from the Lagoa de Jacaré Formation. The first facies consists of a dark gray, fine-grained calcilutit with planar-parallel lamination. The second facies is a marble characterized by light gray to bluish carbonate bands, with no significant sedimentary or deformational structures. These rocks were deposited in a north-south foreland basin over Archean formations of the Belo Horizonte and Divinópolis complexes, which were not affected by the brasiliano event. The tectonic evolution of the Brasília and Araçuaí Belts significantly influenced the structural characteristics of the Bambuí Group, with shallow deformations extending approximately 200 km into the São Francisco Craton. The Brasiliano event (700-500 Ma) caused regional metamorphism in the upper part of the Bambuí Group, reclassifying calcilutits as marbles under high-pressure, low-temperature conditions. This study conducts a comparative geomechanical analysis of calcilutites and marbles, employing tests such as points load, uniaxial compression, slake durability, and acoustic wave propagation. The goal is to evaluate the impact of the deformational and metamorphic processes on the mechanical strength and overall geomechanical behavior of these carbonate rocks.