Index and probability maps of occurrence of iron ore deposits: a proposed geophysical approach developed in Curral Novo do Piauí (PI) State - Brazil - Sato, Enos Nobuo; Almeida, Teodoro Isnard Ribeiro de; Dias, Vilson Marques; Yamamoto, Jorge Kazuo; Cavallaro, Francisco de Assis; Santana, Washington Rydz Rebouças (Brazilian Journal of Geophysics, 2013)