The coal deposits of Peru are in three facies of the Lower Cretaceous Goyllarisquizga Group — the eastern, southern, and western facies. Only the western facies is divided into formations, which are from bottom to top the Oyón, Chimú, Santa, Carhuaz, and Farrat. The most important coalfields are the Goyllarisquizga, Jatunhuasi, Oyón, and the “Northern Anthracite” fields.
The Goyllarisquizga field, in constant production since 1903, has yielded at least 8,800,000 metric tons of bituminous coal, which has been used to make metallurgical coke for the Cerro de Pasco Corporation’s smelter in La Oroya. The coal produced in 1967 averaged 54.0 percent ash, 21.5 percent volatile matter, and 21.5 percent fixed carbon.
The Jatunhuasi field is a long, narrow body of coal east of the continental divide. It has been explored by the Cerro de Pasco Corporation—now Empresa Minera del Centro del Perú (Centromin) — because it constitutes the company’s main source of supply with a resource potential of about 8 million metric tons, although proved reserves are considerably less. The coal beds exhibit characteristics different from those in the Goyllarisquizga field, and the ash content is in general lower than that for coal in the Goyllarisquizga field.
In the Oyón basin both anthracite and bituminous coals occur n i the Oyón Formation. Variations in rank of the coals are either the result of intrusion of granodiorite stocks or of intense tectonic activity during which most of the coal was sheared and shattered.
The coal in northern Peru is of anthracitic rank. The coal-bearing rocks in this area extend from the Santa River valley to the upper Chicama River. Coal beds occur in both the Chimú and Farrat Formations. By far the most important area is the region of the upper Chicama, where a substantial tonnage could be developed if a suitable market could be found.