Ore bodies. Magma Copper
Ore Extraction
The first step is ore extraction. At Magma, sulfide ore is extracted through underground mining at depths of up to 4,000 feet below the surface. (Underground mining operations are used to mine deeper, and richer ore bodies.
Factors influencing the choice of mining method include the size, shape, dip, continuity, depth, and grade of ore body; topography; tonnage; ore reserves; and geographic location.) This ore body is approximately one billion tons, with about 56,000 tons per day hauled to the surface and transported to the mill for subsequent processing.
At Magma, underground mine workings are located between 700 and approximately 4,000 feet below the surface and are accessed by four "production" shafts and three "service" shafts. The service shafts provide intake ventilation and supplies, while the production shafts are used to haul ore to the surface as well as serving as exhaust shafts. The ventilation system circulates up to 1 million cubic feet per minute of forced ventilation air into the underground mine workings. Production and service shaft activities at the mine site are monitored by computer s in the mining surface control room.
The underground sulfide ore body is mined using the block-caving method, which entails blasting sections of the ore body above the grizzly level (used to convey ore) and allowing gravity to collapse horizontal slices of ore. Ore falls through the grizzly level and goes through a series of vertical or inclined shafts that transfer ore to the haulage level into ore cars. At the grizzly level, very large pieces are reduced in size manually with a sledge hammer. A train of ore cars transfers the ore to dump pockets, where it is drawn up to the surface with five ton skips to the top of the production shafts, and dropped into coarse ore storage bins.
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