Soil geochemical prospecting for gold at Marrancos (Northern Portugual)

This paper discusses some geochemical mapping techniques and their effectiv eness in detecting of gold and its pathfinder's geochemical anomalies. The study area (Marrancos area) is situated in Northern Portugal. Gold occurs i n a quartz breccia with pyrite and arsenopyrite hosted by metamorphic rocks (hornfels) and it is present in these two sulphide minerals as inclusions or disseminated in the crystal lattice. In this area, the geochemical anoma lies obtained by isoconcentration mapping of single elements were difficult to interpret. The use of alternative geochemical mapping such as multielem ent halos (additive halos) proved to be effective in the definition of Au, As, Bi, Sb, Te and Se secondary geochemical signature. (C) 2001 Elsevier Sc ience B.V. All rights reserved.