Geology - Porphyry Copper Deposit, Cuajone, Peru

THE Cuajone porphyry copper deposit is the northernmost of a group of three deposits in southern Peru controlled by the Southern Peru Copper Corp.-Toquepala, Quelleveco, and Cuajone— all within a 20-mile belt. Although small pockets of high-grade copper oxide ores were worked in the Cuajone area in the 19th century, it was not until 1939 that its potentialities as a disseminated deposit were recognized by 0. C. Schmedeman. An exploratory drilling pro- gram was begun in December 1942 and continued until early 1945. The program was revived in November 1952 and completed early in 1954. Early exploration was by diamond drilling. Later exploration was predominantly churn drilling, with diamond drilling used only for wildcat holes. Along this northwest-trending belt of deposits. which follows the western slopes of the Andean Range, quartz-monzonite has invaded earlier dio-rite intrusives and a series of warped and tilted Cretaceous volcanic flows. Little faulting of consequence has been recognized within the mineralized areas. Sulfide minerals were introduced into all these diverse rocks, and mineralization was followed by erosion, oxidation, and enrichment. In Late Tertiary and/or Quaternary time the entire