Gold mineralization at Maricunga has been interpreted to be porphyry style gold systems.

The Verde and Pancho gold deposits at Maricunga occur in the Maricunga Gold Belt of the high Andes in northern Chile.

The Maricunga volcanic-intrusive complex is exposed over an area of 12 km2 and consists of andesitic to dacitic domes, flows, and breccias that are intruded by subvolcanic porphyries and breccias (Muntean 1998).

At Verde West, gold mineralization is centered about an elliptical porphyry plug measuring 175 by 100 m and oriented at N30°W. At Verde East, the porphyry plug measures 130 by 80 m and is oriented at N35°E. The porphyries occur within a sequence of intermediate tuffs, porphyries and breccias that are the host rocks to the gold mineralization. Lithological interpretation at Verde has identified six major lithologic units. These are:

• Post mineral intrusives (barren);
• Mineralized post mineral intrusives;
• Verde breccia;
• Dacite porphyry;
• Dacite tuffs;
• Laguna tuff (barren).

The most favourable ore hosts are the Verde Breccia and Dacite Porphyry units. The dacite porphyry is a volcanic to hypabyssal intrusive rock with 20% to 40% plagioclase phenocrysts in a fine-grained matrix. It contains phenocrysts of biotite, hornblende, and sparse quartz. The unit is the best host for stockwork veining, with some portions containing up to 20% quartz-magnetite ± pyrite veinlets.

Maricunga is an open pit mine. The ore is transported by haul truck to the three-stage crusher and then to the heap leach pad.

The Maricunga gold recovery process consists of a single-line primary crushing, fine crushing (secondary and tertiary).

The plant can process 48,000 tonnes per day of dry Maricunga ore. The crushing plant product is approximately 80% passing 12 millimetres.

The ore is transported by haul truck to the three-stage crusher and then to the heap leach pad. Cyanide solution is applied by drip emitters at a concentration on the order of 0.5 grams per liter (g/L) at a rate of approximately 10 liters per hour per square meter (L/hr/m2). The solution percolates and is collected at the base of the pad by drains and pipelines that convey the rich solution to the solution ponds at the Adsorption-Desorption-Refining (ADR) Plant. The ADR Plant uses activated carbon for gold recovery. Cyanide is added to limit the adsorption of copper onto carbon, and a cold cyanide strip of the carbon is performed to remove copper. The cold strip Cu-CN solution is fed back to the heaps. The ADR plant consists of five carbon adsorption tanks, with Zadra pressure elution of carbon coupled with gold electrowinning. Overall gold recovery from ore to gold doré at Maricunga is 65 to 70 percent.

A portion of the rich solution proceeds to the Sulfidization, Acidifica ........