Pyrite zones and Zonal distribution of Cu-Pb-Zn ores in Huanzala Mine, Peru

Abstract

The Huanzala Mine is a copper, lead and zinc mine in Peruvian Andes. Being emplaced in a limestone formation of Cretaceous Period, its ore bodies occur bedded and lenticular in form along approximately definite horizons. Two types of mineralized zones are recognized. One called the inner pyrite zone occurs in the ore horizons such as the mantos from 1 to 5 and is closely associated with Cu, Pb and Zn ores, while the other, the outer pyrite zone, occupies the area between the ore horizons of the former type. The latter type consists of large, massive and replacement ore bodies with scarce association of Cu, Pb and Zn ores.
Distribution of Cu, Pb, and Zn ores is limited to the areas 200 meters from the inner pyrite zone. Zonal distribution of ores is recognized megascopically in the order of pyrite-Cu, Cu-Zn, Zn-Pb and limestone, from the center outwards. The zonal distribution is likewise recognized by using metal ratio, π, Zn=(Assay Zn)/[Assay(Cu+Pb+Zn)×100. Within a mineralized horizon, a few inner pyrite zones are scattered and the matrix is occupied by Cu, Pb and Zn ores. The principle of exploration in the Huanzala Mine is to investigate distributions and shapes of the inner pyrite zones. Metal ratios are helpful to indicate the possible locations of unknown ore zones.