No description available.

El Alacran, northern Sonora, Mexico, is a high-level, Laramide porphyry copper deposit encompassing an east-west elongated altered and mineralized area of 2.7 by 6 km. A small quartz latite porphyry plug forcefully intrudes comagmatic(?) Late Cretaceous or Early Tertiary andesitic to quartz latite volcaniclastic rocks.Veinlet-controlled and pervasive potassic, Type I phyllic, and transition type alteration with related base-metal mineralization postdates pervasive propylitic alteration and is related in space and time to the intrusive and its associated intrusion-breccia annulus. Potassic alteration is dated by K-Ar at 55.4 +- 1.2 m.y. Later pervasive and veinlet-controlled Type II phyllic and minor advanced argillic alteration is associated with intrusive breccia dikes and pipes which are genetically related to degassing of the system. Minor veinlet-controlled late-stage alteration followed. Hypogene zoning is exhibited by alteration, mineralization, total sulfide volume, mineralized fracture density, and geochemistry with zoning being centered over or to the east of the exposed intrusive. Supergene enrichment processes have modified hypogene sulfides, oxides, and silicates and have formed a copper enriched blanket which underlies a leached cap. The blanket is characterized by a chalcocite zone which grades downward into a bornite-digenite-covellite zone and then into low-grade protore. Although the enriched blanket appears to be subeconomic, this study indicates potential for a deep, high-grade protore zone.

No description available.

No description available.

Copper from dump, heap, and in situ leaching accounts for about 15% of United States copper production. In situ leaching is the least understood and most difficult to evaluate of these leaching methods. Several types of supergene copper deposits are derived from porphyry copper systems depending on the geologic and climatic factors involved in the formation of a deposit. The geologic and climatic factors involved in the formation of a deposit. The geologic evaluation of a deposit should provide most of the basic information required to access a deposit for in situ leaching. Metallurgical testing can determine the leachability and acid consumption of the ore as well as the need for an oxidizing agent through the use of agitation and column leaching tests. The location of the deposit with respect to the water table determines the type of ground preparation required. Hydraulic fracturing can be used for deposits below the water table and blasting or caving can be used for deposits above the water table. Fluid flow through the deposit depends on the method of application, the permeability of the deposit, and the method of egress from the deposit. The leaching of a copper "oxide" deposit depends on the strength and volume of sulfuric acid which reaches the ore. The leaching of a copper sulfide deposit depends on an oxidant as well as sulfuric acid reaching the ore.