U N I V E R S I D A D D E C O N C E P C I Ó N DEPARTAMENTO DE CIENCIAS DE LA TIERRA 10° CONGRESO GEOLÓGICO CHILENO 2003 Geology of the MM Copper Deposit, Chuquicamata District – An Update Guillermo Müller and Jorge Quiroga Codelco Chile. Isidora Goyenechea 2934. Piso 5. Santiago, Chile (
[email protected]) MM is a blind porphyry copper deposit covered by approximately 50 m of barren gravel. The central part of the deposit (MM Central) is located ~5 km north of Calama and 8 km south of Chuquicamata. Both shape and location of the MM deposit are related to a complex, NS-trending, 7-km long by ~300-m wide structural system that corresponds to the southern extension of the West Fault of Chuquicamata. To date, this central block has been explored with 100,000 m of diamond drill holes and 2.7 km of underground workings, with current geological resources amounting to 882 Mt @ 1.02% Cu, 15 ppm Ag, and 566 ppm As, for a cut-off grade of 0.25% Cu. The deposit remains open to the north, south and west. The discovery of mineralization west of Mina Sur and on the west side of the West Fault in a single hole by Anaconda in the 60’s, and later in four additional holes drilled by Codelco in the 80’s, suggested the possibility for a left-lateral offset of part of the Chuquicamata deposit and stimulated further drilling. The final discovery during the 90’s by Codelco, of at least 2 km of continous, in-situ “Chuqui-like” mineralization (the MM deposit) on the west side of the West Fault has modified the concept of the displacement, which is now under revision.