Application of 3D magnetic amplitude inversion to Fe oxide-Cu-Au deposits at low magnetic latitudes: A case study from Carajás Mineral Province, Brazil

Abstract

Strong hydrothermal alteration affects rock physical properties in iron oxide–copper–gold deposits (IOCG) and may result in characteristic signatures detectable in geophysical surveys. Magnetic signature is commonly used and 3D inversions are often used to perform interpretation. In areas with strong remanence and self-demagnetization, the total magnetization can have an orientation different from the induced field direction which precludes the use of traditional inversion methods. To overcome this problem, the magnetic amplitude data that are weakly dependent on the magnetization direction was inverted. A case study on applying this approach to the Furnas Fe oxide–Cu–Au deposit at low magnetic latitude in Carajás Mineral Province, Brazil, is presented, and demonstrates that magnetic amplitude inversions can reliably recover the distribution of effective magnetic susceptibility and identify massive magnetite from hydrothermal alterations associated with the high-grade ore.