Multi-metal soil geochemistry: A tool for identification and exploration of porphyry copper deposits: Two examples from Peru

Abstract

Abstract Two porphyry copper-type mineral occurrences were prospected using multi-element soil geochemistry with the purpose of their selection, identification and evaluation and in order to outline a drill target. The two occurrences are located in very different climatic zones: one in the north of Peru at an altitude of 2500 m, in moderate but humid climatic conditions; the other in a warm desert area at an altitude of 1500–1800 m. For each soil sample, Cu, Mo, Pb, Zn, Au, Mn, Fe, and K were determined. In both cases, the values were not significantly influenced by weathering processes except for Cu, which showed high mobility in desert conditions. A system of concentric zoning with Cu, Mo, Au, and K in the center and Pb, Zn, Mn, and Fe forming the outer zone, together with field observations enabled us: (1) to confirm the existence of a zoned hydrothermal system, indicating porphyry copper-type mineralization; (2) to outline a target area for drilling more easily than by using only soil Cu values, which are often unreliable due to the high mobility of the metal; and (3) to follow the migration of elements like Mn, Zn, Fe, and Pb as a result of hydrothermal alteration.