(Translation from Spanish) The Silver Bell district in Arizona provides a good example of various electrical and electromagnetic methods applied to the same porphyry copper deposits. Lowest resistivities in the Silver Bell area corresponded with the quartz monzonite porphyry and with zones of sericitic alteration. Likewise, highest IP responses were associated with sericitic alteration. The low resistivities at Silver Bell are caused by the strongly fractured nature of the porphyry system, particularly in sericitic zones, and its interconnected sulfide veinlets. Sericitic zones are highly conductive because of intense fracturing, abundant pyrite mineralization, and sericitic alteration. The higher resistivities of the potassic zone, on the other hand, reflect silicification, disseminated sulfides (as opposed to sulfides deposited in veinlets), and overall less abundant sulfide and clay minerals. Propylitic zones are less fractured and have much lower total sulfides and, thus, higher resistivities. Resistivity weakly correlates with the leached cap and underlying zones of enrichment. Copper-porphyry mineralization is concentrated over several quartz monzonite porphyry domes and porphyry-cogenetic dykes of Laramide age (69-63 Ma) that were emplaced on a west-northwest-striking structure known as the Silver Bell fault zone. 11 kilometers and include the Oxide, West Oxide, El Tiro and North Silver Bell deposits. The mineable porphyry deposits contain the mineral chalcocite, diss ........

The mine operates four open-pits (North Silver Bell, El Tiro, West Oxide and East Oxide).

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