The Carmen de Andacollo property is owned by a Chilean private company, Compañía Minera Teck Carmen de Andacollo (CDA). Teck Resources Limited own 100% of the Series A shares of CDA while ENAMI owns 100% of the Series B shares of CDA. Teck’s Series A shares of CDA equate to 90% of CDA’s total share equity and ENAMI’s Series B shares comprise the remaining 10% of total share equity.
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Summary:
The Carmen de Andacollo orebody is a porphyry copper deposit consisting of disseminated and fracture- controlled copper mineralization contained within a gently dipping sequence of andesitic to trachytic volcanic rocks and sub-volcanic intrusions. The mineralization is spatially related to a feldspar porphyry intrusion and a series of deeply rooted fault structures. A primary copper-gold sulphide hypogene deposit containing principally disseminated and quartz vein-hosted chalcopyrite mineralization lies beneath the supergene deposit. The hypogene deposit was subjected to surface weathering processes, resulting in the formation of a barren leached zone 10 to 60 metres thick. The original copper sulphides leached from this zone were redeposited below the barren leached zone as a copper-rich zone comprised of copper silicates (chrysocolla) and supergene copper sulphides (chalcocite with lesser covellite).
Carmen de Andacollo deposit has “hybrid” features with elements of Porphyry Copper and Stratabound deposits. The structural domain model consists of the following main faults, sorted by relative age from the oldest to the youngest: 1) Syn-Mineralization: Carmen Fault and Hermosa-Twila-Andacollo Set. 2) PostMineralization: NS and NE Faults. Six big configurable lithology groups were identified: Lower Volcanic Unit, Upper Volcanic Unit, Intrusive Rocks Unit, Breccia Unit, Undifferentiated Rocks, and gravels. Nine mineralization events associated with nine alterations events have been described. The mineralization/oxidation zones at Carmen de Andacollo are controlling influence on the Cu grades. From top to bottom in the profile the major mineralization zones are: Gravel, leached zone and oxide, strong and weak secondary enrichment and primary zone.
Nine mineralization events related to nine alterations events have been described, divided in 3 domains:
a) Primary Mineralization in Late magmatic Domain: chalcopyrite-bornite (traces), magnetite-chalcopyrite and chalcopyrite-molybdenite, related to Potassic Alteration with dominating Secondary Biotite; chalcopyrite-bornite related to Potassic Alteration with dominating Potassic Feldspar; chalcopyrite-magnetite-specularite-(bornite)-pyrite(?) associated with Albitic Alteration; pyrite, pyritechalcopyrite (traces), specularite-chalcopyrite (traces) and magnetite-chalcopyrite (traces) associated with Propylitic Alteration.
b) Primary Mineralization in Phyllic Domain: pyrite, pyrite-chalcopyrite associations in Main Phyllic Alteration; pyrite (coarse), and pyrite-chalcopyrite-tennantite enargite-tetrahedrite associated with Late Phyllic Alteration.
c) Primary and Secondary Mineralization in Argillic Domain: pyrite-cinnabar, pyrite-tennantite-enargite, cinnabar and pyrite-tennantite-chalcopyrite in Intermediate Argillic Alteration; chalcocite, chalcocite-(covellite) and supergene cinnabar (?) associated with Supergene Argillic Alteration.
The mineralization/oxidation zones at Carmen de Andacollo are a controlling influence on the Cu grades. From top to bottom in the profile the major mineralization zones are:
Gravel
This is generally considered to be recent transported sediments. There are a few instances where this material is (was) old waste dumps from historic underground mines. Any material in this zone that contains Cu grades has already been mined.
Leached Zone and Oxide
The Leached Zone is defined by the presence of Fe-Oxides without Cu-oxides or any sulphides. The Oxide Zone is defined by the presence of Fe-Oxides and Cu-oxides without any sulphides. These two zones were combined for the estimation. The logged presence/absence of Copper oxides did not create a visible correlation to the Cu grades. There were significant grades within material logged as Leach (i.e. no visible Cu oxides) that would make the separation of these zones questionable.
Strong Secondary Enrichment (ESEC1).
This zone is traditionally referred to as the Supergene Zone. It is defined by the presence of secondary Cusulphides, predominantly chalcocite, without the presence of chalcopyrite. While most drillholes showed this contact as a sharp contrast in CNCu there were some drillholes (~5%) that showed significant enrichment beyond this point. A second interpretation pass was needed displaying the CNCu value. If there was significant CNCu beyond the logged contact then the contact was moved to the point at which there was a sharp decline in CNCu grade.
Weak Secondary Enrichment (ESEC2).
This zone is defined by the presence of Chalcocite and Chalcopyrite. The logging of small amounts of Chalcocite is inconsistent so this boundary contains significant amount of interpretation. It was considered that with the presence of Chalcopyrite, the dominant grade variability characteristics are the same as the Primary zone.This zone was used for defining Metallurgical characteristics.
Primary Zone.
This zone is defined by the presence of primary minerals such as Chalcopyrite, Pyrite, Bornite, Tennantite, and no secondary Cu. PRIMC: Primary Zone featuring cavities. Rock fractures and cavities do not evidence or may be partially filled with gypsum. In the case of the latter, the roof of this area is called a “sulphate top” (TDSO4). PRIMS: Primary Zone with no cavities. Rock fractures and cavities are completely filled with gypsum (±anhydrite). The roof of this area is called a “dominant sulphate top” (TDSO4) and marks the end of supergene activity at the deposit. Top of carbonate – TCO3: Surface that marks the upper limit of the area featuring fractures and veinlets filled with calcite. Water is noticeably less acidic under this limit than the water above the limit.