Mineralization

Geology

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Mineralization

(last updated 04/08/2009)

Secondary Cu Mineralization

Secondary (supergene) mineralization occurs at Haquira East as copper oxide minerals and locally the development of a secondary chalcocite blanket. The mineralogy and origin of the Haquira secondary minerals were studied by Prof. William X. Chavez of the New Mexico Institute of Technology in Socorro, on behalf of Antares.

Most of the secondary mineralization is characterized by black copper oxides (principally tenorite), Cu-bearing goethite, and pitch limonite, suggesting a low-pyrite system. Brochantite and chrysocolla are commonly associated with the oxidation of chalcocite. Chalcocite “blankets” are best formed in and proximal to structures. Given the high permeability, the structures are sites of repeated leaching/enrichment as manifested by the rare occurrence of cuprite, chalcotrichite, and native copper. Minor malachite has also been identified. Photos 1 to 3 show examples of the secondary mineralization found at Haquira West and East.

Photo 1: Secondary Copper Oxide Mineralization.

Photo 2: Mixed Secondary Copper Oxide and Secondary Sulphide Mineralization.

Photo 3: Secondary Sulphide Mineralization.

Primary Cu-Mo-Au Mineralization

The primary (hypogene) mineralization at Haquira East is of porphyry-copper type, spatially associated with a stock-like intrusive body of Haquira Porphyry and associated dyke swarms (Figures 36 to 47). Primary mineralization consists of chalcopyrite, bornite, molybdenite, with peripheral pyrite forming a “pyritic-halo” on the deposit. Classic sheeted and stockwork vein systems of dominantly chalcopyrite, bornite, molybdenite, and lesser pyrite are common (Photos 4 to 10). The primary sulphides occur beneath a blanket-like zone of secondary Cu mineralization and an upper zone of leach cap and colluvium.

Photo 4: Mineralized sheeted quartz vein sets within the Haquira East porphyry.

Photo 5: Chalcopyrite, bornite, and molybdenite bearing quartz vein stockwork.

Photo 6: Molybdenite and bornite bearing quartz veins, Haquira East porphyry.

Photo 7: Sheeted quartz-molybdenite-bornite-chalcopyrite veins, Haquira East.

Photo 8: EDM (early dark micaceous) vein halos (green).

Photo 9: Mineralized and altered fine-grained sedimentary wall rocks.

Photo 10: Chalcopyrite-bornite mineralized quartzite sedimentary wall rock.

The CuT (%) grade distribution (Figures 1 to 8), Mo (%) grade distribution (Figures 9 to 16), and Au (ppm) grade distribution (Figures 17 to 24) for each 100 m section through the Haquira East deposit reveal the geometry of the mineralization. High-grade copper (>1 % CuT) forms a sub-vertical, sheet-like body with bornite-rich zones typically containing elevated gold values (> 0.1 g/t). Molybdenite mineralization appears to form a shell-like cupola that is coincident with the top and margins of the main porphyry body. Quartz- and sulphide-bearing stockworks and sheeted-vein systems typical of porphyry copper systems have been recognized in these intrusive rocks and the surrounding sedimentary stratigraphic section, especially in proximal silicified and hornfelsed fine-grained sedimentary rock units. The primary mineralization exhibits a strong structural control, with the primary sulphide minerals occurring in well-fractured structural zones and as disseminations; both within the host porphyry intrusive rocks and within the surrounding fine-grained sedimentary rocks and quartzites (Photos 4 to 10). Some of the higher-grade copper mineralization is associated with early dark micaceous (EDM) veins which form at >600°C and contain abundant disseminated bornite and chalcopyrite (Photo 8).