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

Abstract

PROCESSINGAND INTERPRETATION OF AIRBORNEMAGNETICDATA FROM ITABlRA-FERROS PROJECT, MG: A TOOLSUPPORTING LITHOLOGICALANDSTRUCTURAL MAPPING. The area covered by the Itabira-FerrosProject is located in the lron Quadrangle, State of Minas Gerais, and is known for its emerald occurrences. The area is characterizedby greenstonebelts (Rio das Velhas Supergroup)and paleoproterozoiciron sequencesbelongingto the Minas Series, insertedin granitoid bodies (BorrachudosGranite).The developmentof emerald deposits is attributedto the interactionof pegmatiticfluids with mafic-ultramafic rocks ofRio das Velhas Supergroup. The present study applies geophysicalcharacteristics, using airborne magnetic data and their integrationwith geology,to determine probable zones of emerald mineralization. Analysis and interpretation of geophysicalimagessuggestthe presence ofthree basic types of signaturescomposingthe magneticrelief: the first composedby low spatial frequencysignals,the second by medium frequencies, and the third by high spatialfrequencies. The first group seems to indicate sources forming waving and continuous trends with a NE-SW general direction, in the northern, northwestern, and northeasternportions. The second group, in the central portion, shows a behavior associatedwith large fauItedblocks with a general NE-SW orientationand crossed by E-W and NW-SE structures.The third group also shows a behavior associatedwith large magnetic blocks (faulted geologic blocks) with a WSW-ENE orientation.Analysis and interpretation ofthe mentioned images suggests the presence of three deformationevents. The lineamentDI represents the preferentialdirection of alignment,NE-SW. ln the central region ofthe area, there is a sigmoidal feature that, probably,may reflectthe Pedra Branca shear zone, with dextral movement.LineamentD2 cuts lineamentsin the E-W direction,indicating,probably,a transcurrentsystem offaults with a sinistrai movement,indicatedby DI lineamentbeing displacedby D2 fauIts, as observed in central and northernportionsofthe area. Other brittIestructuresare present in the N400W direction.