Tyrone

Overview

Tyrone is a porphyry open-pit copper mine and processing facility. The mine is among the lowest grade ore bodies in the Freeport-McMoRan mining portfolio.

The mine is located in Grant County near Silver City, approximately, 16 km south of Silver City, New Mexico.

Prior to 1860, Indians mined turquoise at the site. Phelps Dodge acquired mining claims in the area from 1909 to 1916, and began concentrating ore produced from large-scale underground mining in 1916. Operations ended in 1921.

The property returned to operation as an open pit in 1967, with copper production from a concentrator. The solvent extraction/ electrowinning (SX/EW) plant was commissioned in 1984. Tyrone's concentrator suspended operations in 1992 when the property made the transition to 100% SX/EW production.

Location

The mine is located in southwestern New Mexico in Grant County approximately, 16 km south of Silver City, New Mexico. It is located along State Highway 90. The site is accessible by paved road and rail.

Close to the mine site and the Silver City is Fort Bayard were military garissons were stationed during the Apache wars to help protect the miners and dwellers from Geronimo and its followers.

The Tyrone operation encompasses approximately 35,200 acres, comprising 18,755 acres of patented mining claims and other fee lands, and 16,445 acres of unpatented mining claims.

Tyrone is located in a desert environment with rainfall averaging 16 inches per year.

Geology

Tyrone is a porphyry copper deposit type. By size is the second largest porphyry copper deposit in New Mexico.

The Tyrone mine is in the Basin and Range province along the southern margin of the Mogollon-Datil volcanic field.  The Mogollon-Datil volcanic field straddles the transitional boundary between the tectonically stable Colorado Plateau to the north and the extensional terrane of the Basin and Range to the south.

The mining district is in the northwest-striking Burro Mountain uplift. The northwest-trending structural grain in southwestern New Mexico is primarily the result of Jurassic rifting and subsequent Laramide compressional deformation.  The mineralization is in and around the Tyrone stock, a 53 to 57 million-year-old quartz monzonite porphyry that is just one of many intrusions emplaced across southern Arizona and southwestern New Mexico during Laramide deformation 80 to 40 million years ago.

The initial copper mineralization of the Tyrone stock was low grade and not economic. The mineralized rocks were brought toward the surface by uplift and erosion, where the rocks interacted with groundwater.  The copper was concentrated later during weathering of the stock near the earth's surface. (New Mexico Bureau of Geology and Mineral Resources)

Mineralization is predominantly secondary sulfide consisting of chalcocite with leachable oxide mineralization consisting of chrysocola..

As of December 31, 2011 proven and probable mineral reserves were estimated at 148 million tons grading 0.29 per cent copper for a total of 0.7 billion pounds recoverable copper.

Mining & Operation

Tyrone open pit mining complex has been in operation since 1967.

The available mining fleet consists of 20 240-metric ton haul trucks loaded by three shovels with bucket sizes ranging from 17 to 47 cubic meters, which are capable of moving an average of 136,000 metric tons of material per day.

A combination of mining and reclamation activities at the open-pit is usually conducted at the same time. Historically, ore production has occurred from numerous open pits throughout the site. Mining is currently ongoing in a single, large, central open pit.

The highest bench elevation is 2,000 meters above sea level and the ultimate pit bottom is expected to have an elevation of 1,500 meters above sea level.

Processing

Tyrone produces all copper by the solvent extraction / electrowinning (SX/EW) method. The run-of-mine (ROM) material is directly placed on the leach pads where low grade ore is leached and the pregnant solution is recovered through a solvent extraction process followed by an electrochemicall process known as electrowinning. The final product is copper cathode.

The mining and processing operation receives electrical power from the Luna Energy facility and from the open market.

Environment & Community

The New Mexico regulators request that the mining operation submits a closure plan that must include measures to assure meeting groundwater quality standards following the closure of discharging facilities and to abate any groundwater or surface water contamination. Some of these requirements that are currently being disputed by the company could result in increases in Tyrone closure costs.

The tailings reclamation process is being done by earthmoving equipment that grade the side slopes and prepare them for capping with soil. A system of water diversion system is being incorporated to assure that soils are not washed off by rain. Then the area is reseeded with native grasses and shrubs that are suitable wildlife habitats.

In 2011, reclamation of the rock stockpiles continued in the south and east perimeter of the operation. Old mining facilities were also dismantled.