• Independent Geologist’s Report on Copper Hill Porphyry Cu-Au-Mo Project received;
• Discovery of potentially large-scale mineralised porphyry confirmed;
• Alteration-transition zones noted in drill-core are important mineralisation guides;
• Surface geochemistry supports evidence from drilling of new central and eastern target zones;
• Leached cap, supergene zone and deeper primary zone drill targets identified;
• Shallow leached cap – supergene zone drilling recommended;
• Primary zone drilling recommended;
• Rhenium-molybdenum and other valuable metal associations recommended for investigation.
Argentina Mining Limited (Argentina Mining or the Company) (ASX:AVK) is pleased to advise that it has received from Chilean independent geological consultants GeoscanEx S.A.2 a comprehensive and detailed report, entitled Copper Hill Project, San Juan Province, Argentina NI 43-1011 Technical Report, 27 February 2012 on the progress of the Company’s exploration at the Copper Hill Copper-Gold-Molybdenum Prospect (“Copper Hill”), currently the Company’s principal focus of exploration within its Cerro Blanco Project in San Juan Province, Argentina.
Argentina Mining contracted the services of GeoScanEx SA to provide this independent assessment of exploration at Copper Hill, which includes results from the Company’s maiden diamond drilling campaign undertaken between April and December 2011. This drilling was conducted in two phases; an initial “proof of concept” phase, followed by a second phase of three deep drill holes. This drilling intersected broad zones of primary porphyry copper-gold-molybdenum sulphide, overlain by supergene and leached zone oxide mineralisation.
The objective of the independent assessment was to provide an opinion on the potential of the Copper Hill Prospect for discovery of an economic porphyry copper-gold-molybdenum deposit and to recommend directions for future exploration.
After reviewing all exploration undertaken at Copper Hill and undertaking independent fieldwork, including further mapping and sampling at the project site, Geoscanex concluded that:
• The Copper Hill porphyry Cu-Au-Mo deposit shares the characteristics of other well-known large-scale Andean porphyry copper-style deposits developed in and around Tertiary-age dacitic porphyries which have intruded older Permo-Triassic volcanic and intrusive complexes, and has the potential to attain the status of a world-class deposit.
• The geological characterisation of the deposit and its location in a well-defined belt of continental porphyry copper deposits makes it possible to anticipate potential for a large volume of mineralization, which can be corroborated from the results of geophysics.
• From the studies undertaken, only a minor portion of the main mineralized body is known, principally on the western edge of Copper Hill, while results from surface mapping, geochemistry, geophysics and drilling indicate that only a peripheral western mineralised zone has been intersected in drilling to date, and that indicated potentially higher grade central and eastern zones remain to be tested.
• The results of the geochemical distribution of copper, molybdenum and gold grades at surface enable significant inferences to be made with respect to the potential to discover other areas of greater prospectivity and mineralized volume potential.
• The deep primary mineralisation intersected in drilling by Argentina Mining is dominantly pyrite and chalcopyrite.
• A pronounced copper-gold mineralized leached cap has developed at surface, with an average thickness of about 20m.
• At a greater depth and of similar thickness to the leached cap, a zone of supergene copper oxides has developed. This zone is composed mainly of malachite, chrysocolla, turquoise and azurite. If further drilling indicates this zone to be laterally persistent it may prove economically significant.
• Phyllic quartz-sericite alteration is the most common alteration process and is of the most extensive distribution; this alteration style interfaces with abundant potassic alteration and is expressed mainly as veins and stock-works of quartz or gypsum.
• The transition zone from phyllic to potassic alteration styles noted in drill-core is associated with increasing mineralisation and is of great significance as a guide to determining areas of possible higher grade mineralization.
• Disseminated bornite, chalcocite and covellite occur in some places, in association with pyrite and chalcopyrite, especially at the important phyllic-potassic alteration interface. These zones probably result from hypogene alteration of pyrite and chalcopyrite respectively and are often of notably higher grade, attaining copper grades of 0.7% Cu, with molybdenite concentrations up to 600ppm Mo or higher. An increase in copper, molybdenum and gold values is noted in a 75m interval between 240m and 315m depth in diamond drill-hole MC-3 and is related to this alteration interface.
• The hydrothermal alteration and mineralization system of Copper Hill is influenced by major controlling NNW to NW-trending structures on which normal faults have displaced mineralized blocks, especially in a vertical direction, such that in some cases primary mineralization may be observed at surface.
• The results of three separate geochemical surveys shows higher levels of surface copper anomalism in the western sector of Copper Hill, with a distinct ring of relatively anomalous copper values in the vicinity of the known mineralized body.
• Molybdenum anomalism coincides with that of copper, although other interesting molybdenum anomalism appears to be controlled by important structural trends in the eastern sector of Copper Hill, which has not yet been tested by drilling.
• Given the generally strong copper-molybdenum association, anomalous molybdenum in the eastern zone may be a useful indicator of copper potential in that area.
On the basis of their conclusions, GeoScanEx recommended:
• Additional detailed geological and structural mapping.
• A study of the relationships between limonite and other iron oxides found at surface in the leached cap and in secondary and primary copper-bearing oxides.
• Study the geochemical distribution of molybdenum, as an exploration guide to higher grade copper-gold-molybdenum mineralisation.
• A trial analysis for rhenium in high grade molybdenum samples and to examine other potentially valuable metal associations.
• Undertake 1,650m of shallow drilling penetrating below post-mineralisation volcanics to explore the leached cap, supergene zones and shallower primary sulphide zones.
• Undertake 2,550m of deeper inclined and vertical diamond drilling to locate higher grade primary Cu-Au-Mo mineralisation in the inferred central and eastern mineralised zones.
The Board of Argentina Mining Limited is greatly encouraged by the conclusions and recommendations of the Independent Geologist’s Report and their value in providing future exploration direction at Copper Hill.
The findings of the report provide strong support and direction for the existence and location of as yet untested potentially larger volumes and higher grades of porphyry Cu-Au-Mo mineralisation, copper-gold leached cap deposits and copper-rich supergene deposits, .
The Board is now carefully considering these findings and examining drilling options, with a view to recommencing drilling at Copper Hill later in 2012.
Figures 1 and 2 below show schematic cross-sectional relationships between existing drill hole intersections and new target zones for primary, leached cap and supergene zone mineralisation.