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Location: 97 km NW from San Juan, Argentina
Level 1, 100 Havelock StreetPerthWestern Australia, Australia6005
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The Hualilan Project is the site of extensive zinc skarn mineralisation with a gold overprint which makes it a somewhat unique style of mineralisation.Commonly zinc skarns occur in continental settings associated convergent tectonic plate margins as is the case at Hualilan, located in the pre-cordillera of the western South American convergent plate margin. Zinc skarns commonly contain high grade zinc, lead, and silver although zinc is usually dominant. Mineralisation and skarn alteration at Hualilan occurs in all three main rock types.1. Limestone (San Juan Formation of Ordovician age) contains high grade mineralisation (manto style) controlled by bedding parallel faults, cross faults, and contacts with other rock types.2. Shale and sandstone (of Silurian age) contains lower grade replacement style skarn mineralisation which preferentially occurs parallel to bedding with 30m of the Limestone contact.3. Dacitic intrusions (of Mid-Miocene age) contain stockwork fracture and locally breccias which host lower grade skarn mineralisation.In all host rocks, the zinc skarn mineralisation is overprinted by a slightly later phase of gold - silver mineralisation. This second phase of mineralisation is mesothermal to deep epithermal and may be related to but is separate from the zinc skarn. Importantly, the gold mineralisation is deposited in the same reactivated faults and fractures as the zinc skarn. Precise mineral paragenesis and hydrothermal evolution of the deposit is the subject of on-going work which is being used to guide exploration and detailed geometallurgical test work.The dacitic intrusions which are part of the host rock sequence at Hualilan may be related to the hydrothermal activity that formed the skarn, although the timing relationships have not been determined. Gold occurs in native form as inclusions with sulphide (predominantly pyrite) and in pyroxene-garnet skarn alteration. The mineralisation commonly occurs with pyrite and the zinc skarn assemblage of sphalerite and galena with rare chalcopyrite, pyrrhotite and magnetite. Importantly, mineralisation contains very low levels of arsenic, mercury, and other deleterious metals.Complete oxidation of the surface rock due to weathering is thin. A partial oxidation/fracture oxidation layer near surface is 1 to 40m thick and has been modelled from drill hole intersections.Where oxidation is more intense, native gold can be observed. This oxide mineralisation has been the subject of past mining at Hualilan with an unknown amount of gold having been extracted by washing and more recently by vat leach.Dimensions31 separate domains were interpreted over a strike length of 2.3kms. The domains vary in width and orientation from 2m up to 100m in width. The deepest interpreted domain extends from the surface down approximately 600m below surface.
