Aura Minerals holds the Aranzazu Property indirectly through its 100% owned subsidiary Newington Corporation S.L. (Newington) which, in turn, holds 100% of the Aranzazu Property through its Mexican subsidiary Aranzazu Holding S.A. de C.V. (Aranzazu Holding).
Aranzazu Holding S.A. de C.V. (“Aranzazu Holding”), the operating entity for the Aranzazu Mine.
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Summary:
The Concepcion Del Oro district represents a porphyry copper deposit that has been eroded down to a relatively deep level, as evidenced by the outcropping skarn alteration. Skarn alteration is barren unless the skarn is overprinted by the later porphyry style alteration marked by propylitic, phyllic and potassic alteration types. Trace metal geochemistry supports the classification of Concepcion del Oro as a porphyry deposit. Strongly anomalous bismuth, tellurium, arsenic and antimony are present and are typical trace metal assemblages associated with porphyry copper deposits. This trace metal assemblage is most anomalous in areas of phyllic and potassic alteration.
The mineralization in Aranzazu has a strike length of 1.5 km, a width of up to 250 m and depth extents up to 600 m. The Aura Minerals’ exploration and definition drilling shows that mineralization is closing off at BW, Mexicana and AA but open at depth in Glory Hole Porfido zone. The deepest drilling conducted to date was carried out by Aura Minerals indicated the presence of strong copper mineralization at an elevation of 1,500 m, or 600 m below surface.
Copper, gold and silver mineralization occurs in a porphyry alteration assemblage related to the intrusion of an igneous rock complex consisting of quartz monzonitic to granodioritic rocks. The igneous rocks have intruded a sequence of Jurassic to Cretaceous limestones and siltstones. The sedimentary rocks have undergone contact metasomatism and skarnification and now represent a group of rocks ranging from endoskarn and exoskarn, proximal to the intrusive, to marble, distal to the intrusive. Hornfels is present and reflects the contact metasomatic alteration of clastic rocks. Porphyry alteration consisting of propylitic, phyllic and potassic alteration overprints the skarn, quartz monzonite and, in some areas, marble and hornfels. The porphyry alteration is the mineralizing event that deposited the suite of metals that comprise the mineral deposits of interest.
The copper mineral species present in the different zones vary depending on the alteration style that is prevalent. In the BW zone, host to propylitic alteration, the copper mineralization is mostly chalcopyrite. Copper mineralization present in phyllic and potassic alteration styles is chalcocite, copper sulphosalts, chalcopyrite and bornite. The trace metal assemblages also vary depending on the copper minerals present. The BW zone contains moderate amounts of arsenic, but is relatively low in antimony, bismuth and tellurium. In areas of phyllic and potassic alteration where multiple copper mineral species are present, the amounts of arsenic, antimony, bismuth and tellurium increase.
Other phases of mineralization are evident in the Concepcion Del Oro area. Zinc-lead-silver deposits are noted as discrete, relatively small chimney and manto deposits. The zinc-lead-silver mineralization phase is present as both distal deposits relative to the Arroyos Azules copper mineralization and as late stage mineralization that postdates and cross cuts the Arroyos Azules copper mineralization.
Some skarn and intrusive zones contain high concentrations of molybdenum. Often garnet skarn contains several percent of coarse grained molybdenum and it is also common in veins which cut skarn and intrusive. Molybdenum occurs within weakly propylitized endoskarn and exoskarn, though it is not clear from geological relationships where the molybdenum mineralization occurs paragenetically relative to the copper and zinc-lead-silver pulses of mineralization. Molybdenum grades do not return assays that would be considered economic.
Gold mineralization occurs throughout all of the alteration phases previously mentioned with the exception of skarn alteration. Gold grades are generally higher in the phyllic and potassic alteration assemblages compared to propylitic altered rocks.