Both Escondida and Escondida Norte are porphyry copper deposits, being the deposit type typical of the majority of Chilean/Andean copper deposits. The deposits lie in the Escondida-Sierra de Varas shear lens of the Domeyko Fault System. The deposits are supergene-enriched copper porphyries with primary mineralisation associated with multiple phase intrusions of monzonite to granodiorite composition into host volcanics. The deposits are related geographically and geologically to porphyry bodies intruded along a regional lineament which exerts strong control over the regional distribution of deposits of this age and type. The Escondida cluster is formed by the Escondida (including Escondida Este) and Escondida Norte - Zaldívar porphyry copper deposits. The latter corresponds to the same ore body mined by two different companies and operations. Additionally, the porphyry copper deposits of Chimborazo and Pampa Escondida, as well as Pinta Verde, have been recognised. Escondida Deposit Alteration and Hypogene Mineralisation Much of the feldspathic porphyry shows sericitic alteration in shallow levels already exploited an advanced argillic zone and at deeper only along fault zones. Quartz, pyrophyllite and subordinate alunite, diaspore, and svanbergite are reported (Brimhall et al., 1985; Alpers and Brimhall, 1988). At depth and as remnants in the sericitic zone, patches of chlorite-sericite alteration exist, which give way downward to biotite in andesitic volcanic rocks and k-f ........

Minera Escondida Limitada(MEL) is a mining operation that uses conventional open pit methods to extract mineral reserves containing economic quantities of copper to produce both cathodes and copper concentrates. The mineral reserves are based on the LOM plan which only considers open pit mining. Since the start of operations at MEL, the mine has operated using an open pit mining method, utilising trucks, and shovels/excavators. This method is suited to the large copper porphyry deposits mined by MEL as the deposits are low grade, high tonnage and located relatively close to the surface. Drill and Blast The mining operation begins with the drilling process; drill samples are sent to an assay laboratory for analysis. The assay results are used to mark out zones of ore, leach, and waste rock, which are mined separately. Waste Removal and Storage After the blasting is completed, ore and waste are mined by excavators loading onto trucks. Overburden and waste loads can be used for fixing roads, building ramps, or simply placed on the Overburden Storage Facility. The mine design criteria are listed below: • Surface mining approach • Minimum operating width of 80 m • Haul road design width of 40 m • Bench height of 15 m • Maximum road grade of 10% • Bench face angle and catch berms vary based on geotechnical sector • Typical blasting grid ranging from 7x7 until 11x14m • Final wall Control Drill Pattern 2.0, 2.5 and 3.0 m depending on sector • Blasthole diameter of 6.1/2, 9, 10 ........

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