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Abstract
Deposits of copper-cobalt-zinc mineralization at Boleo occur within widespread, stratiform clay-rich horizons or beds known as "mantos" (manto is a Spanish term used in mining parlance for a general mineralized layer or stratum). Within Boleo formation stratigraphy there are seven identified mantos, including two of very limited extent, that occur as relatively flat to generally shallow dipping, stratabound and stratiform beds. These include, with increasing depth, manto 0, 1, 2, 3AA, 3A, 3 and 4, whilst recent work has suggested a possible 8th manto, 4A above manto 4. Historically the major producing manto has been manto 3, which yielded approximately 83% of historic production between 1886 and 1985, when the original mine was shut down. Most of the remaining production has come from manto 1 in the southeast portion of the Boleo area where manto 3 is absent.