ASARCO geologists first discovered the Sacaton mineral deposit in the early 1960s while examining an outcrop of leached capping composed of granite cut by several thin monzonite porphyry dikes. The nature of this original find indicated the likely presence of porphyry copper-type mineralization. Following this lead, ASARCO initiated a drilling program which defined copper mineralization zones. The west zone contained the ore body which was ultimately accessed through the open pit. The deeper east zone was the target of potential mining by underground methods.
Project construction and mining of the west zone via open pit method commenced by 1972, and the mine operated continuously from 1974 until 1984. An underground copper deposit at Sacaton was under development until September 1981 when work was suspended because of high costs and a weak copper market. The Sacaton mine was permanently closed on 31 March 1984 due to exhaustion of the open pit ore reserves.
The resultant Sacaton open pit mine is roughly circular, approximately 3,000 ft (914 m) in diameter and 1,040 ft (317 m) deep. The pit also has a visible internal lake with the surface at approximately 980 ft in depth from the pit rim. During operation, the Sacaton mine consisted of the pit, crushing facilities and coarse ore stockpile, a 9,000 tpd flotation mill, a tailings storage facility (TSF) that covered approximately 300 acres, a return water impoundment, an overburden dump, and a waste rock dump that covered approximately 500 acres.
Production from the open pit was approximately 11,000 tpd. Copper flotation mill concentrate was sent by rail to the ASARCO smelter in El Paso, Texas. Over the mine’s operating life, 38.1 million tons of ore were mined and processed, recovering 400M lb of copper, 27,455 oz of gold, 759,000 oz of silver. During mining of the open pit, a waste dump was created through dumping of defined waste material. All oxide copper mineralization, and sulfide copper mineralization below the working grade control cutoff of 0.3% copper (Cu), were deposited to the waste dump. The historic waste dump forms the basis of the Stockpile Project which is part of the Cactus re-development plan.
The table below provides Sacaton Mine Historic Production (fiscal years ended 12/31)
Source: Sacation Mining Operations Report Version 2005 By David F. Briggs 10/22/2004