Magnetic soils from mafic lithodomains in Brazil

Tropical soils typically retain high amounts of iron oxides and some of them are magnetic, in the sense that their spontaneous magnetization sigma > 1 JT(-1) kg(-1). The two major orders forming on mafic domains, namely dusky red Oxisol and Alfisol, generically re ferred to as terrae rossae, are the most representative magnetic soils and cover as much as 3.9% (similar to 330 000 km(2)) of the Brazilian land area. In this paper, an up-to-date overview is presented, dealing with selected magnetic soils forming on four representative examples of mafic lithology. Some aspects of their iron oxide mineralogy and field and laboratory methodologies of study are discussed.