Páginas 337-388, 8 mapas | Preparado en cooperación con el Instituto Nacional de Investigación y Fomento Mineros, Ministerio de Fomento y Obras Publicas del Perú bajo el auspicio de Foreign Operations Administration, United States Department of State.

The Atacocha lead-zinc mine, 15 km northeast of Cerro de Pasco in Central Peru, was the object of a detailed geologic investigation in 1952 by geologists of the Instituto Nacional de Investigación y Fomento Minero and the U.S. Geological Survey. The mine is about 4,000 m above sea level, in an area of steep topography with about 900 m of relief. Rocks exposed at Atacocha consist of limestone, chert breccia, quartz sandstone, and basalt that range from Late Triassic to Early Cretaceous in age. These rocks have been intruded by dacite of probable Tertiary age. The most prominent structural features are the east limb of a large anticline east of the mine, and a south-plunging syncline to the west. The two folds are separated by a major fault zone. The rocks west of the fault have been dragged along it and are bent into a small cross fold, which seems to be the primary control for the local...