PROCESSAMENTO E INTERPRETAÇÃO DE DADOS MAGNETROMÉTRICOS AÉREOS DO PROJETO ITABIRA-FERROS, MG: UMA FERRAMENTA NO AUXÍLIO AO MAPEAMENTO GEOLÓGICO-ESTRUTURAL

Abstract

The area covered by the Itabira-Ferros Project is located in the lron Quadrangle, State of Minas Gerais, and is known for its emerald occurrences. The area is characterized by greenstone belts (Rio das Velhas Supergroup) and paleoproterozoic iron sequences belonging to the Minas Series, insertedin granitoid bodies (Borrachudos Granite). The development of emerald deposits is attributed to the interaction of pegmatitic fluids with mafic-ultramafic rocks of Rio das Velhas Supergroup. The present study applies geophysical characteristics, using airborne magnetic data and their integration with geology, to determine probable zones of emerald mineralization. Analysis and interpretation of geophysical images suggest the presence of three basic types of signatures composing the magnetic relief: the first composed by low spatial frequency signals, the second by medium frequencies, and the third by high spatial frequencies. The first group seems to indicate sources forming waving and continuous trends with a NE-SW general direction, in the northern, northwestern, and northeastern portions. The second group, in the central portion, shows a behavior associated with large faulted blocks with a general NE-SW orientation and crossed by E-W and NW-SE structures.The third group also shows a behavior associated with large magnetic blocks (faulted geologic blocks) with a WSW-ENE orientation. Analysis and interpretation of the mentioned images suggests the presence of three deformation events. The lineament D1 represents the preferential direction of alignment, NE-SW. In the central region of the area, there is a sigmoidal feature that, probably, may reflect the Pedra Branca shear zone, with dextral movement. Lineament D2 cuts lineamentsin the E-W direction, indicating, probably, a transcurrent system of faults with a sinistral movement, indicated by D1 lineament being displacedby D2 faults, as observed in central and northern portions of the area. Other brittle structures are present in the N40°W direction.