Market Survey on Copper - Indian Bureau of Mines

In late 1997, Antofagasta sold a 25% stake in Minera Los Pelambres to one
Japanese consortium and a 15% holding to another. With partner project finance loans
secured, mine development started immediately, and production began in December
1999. Fresh water supply is drawn from three mountain streams but is carefully
recycled. Electricity is taken from the grid via a dynamically controlled DC-link.
Antofagasta plc now owns 60% and manages the operation, which employs 521
people, via Antofagasta Minerals SA. One partner consortium comprises Nippon
Mining and Metals Co. Ltd (15%), Marubeni Corp. (8.75%) and Mitsui & Co. Ltd
(1.25%), while Mitsubishi Materials Corp. (10%) and Mitsubishi Corp. (5%) make up
the other. Nippon Mining & Metals and Mitsubishi Materials planned to take delivery
of approximately half the concentrate output.
Reserves
Porphyry copper mineralisation – chalcopyrite, chalcocite, bornite, covellite and
molybdenite – makes up a resource of 3,000Mt grading 0.65% Cu and 0.014%
molybdenum. By end-2005, the reserves figures were: proven – 831Mt grading 0.68%
Cu, 0.019% Mo, 0.034g/t Au and 1.2g/t Ag; probable – 655.9Mt grading 0.67% Cu,
0.016% Mo, 0.032g/t Au and 0.93g/t Ag; and possible – 525.2Mt at 0.59% Cu,
0.0138% Mo, 0.033g/t Au and 0.57g/t Ag.
By 2008, a two-stage exploration programme to identify additional reserves was
completed. The drilling programme identified an additional 1.9 billion tons of
resources.
Mining
The mine is an open pit sized 2.5km x 2.2km at surface, which is at an altitude
of 3,100m above sea level (asl). Three Ingersoll-Rand electric rotary rigs drill
blastholes, the initial two P&H 4100AS mining shovels and a LeTourneau L-1800
wheel loader, plus a 4100XPB shovel added later, work with a haulage fleet of five
329t-capacity Caterpillar 797 haul trucks to shift waste and ore in equal proportions.
The mine works two 12-hour shifts.
Processing
Trucks feed an FFE Minerals 60” x 110” in primary gyratory crusher and a
sophisticated overland conveyor system engineered by Thyssen Krupp takes the ore
13km to the stockpile at the concentrator, which is down at 1,620 m. In its first full
year, 2000, Los Pelambres processed 34 Mt of ore to produce 298,900t of copper-inconcentrate
and 5,450t of molybdenum.
Two 17,000 hp FFE Minerals 36ft x 19ft SAG mills work with four 9,500hp
FFE Minerals 21ft x 33.5ft ball mills, giving a throughput of about 85,000t/d. In 2001
Los Pelambres decided to install pebble crushing to improve the SAG mill
performance, and Bechtel designed an upgrade programme to raise the throughput to
114,000t/d. FFE supplied a redesigned SAG discharge system for this project. The
pebble crusher was installed in August 2003 and had an immediate positive effect.
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