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Location: 117 km SE from Wiluna, Western Australia, Australia
Level 4, 500 Hay StreetPO Box 2008, WA 6904SubiacoAustralia6008
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Orelia is Archean gold mineralized deposit that is part of the Yandal Greenstone belt. The stratigraphy dips approximately 60 degrees towards the west and strikes largely north-south. The oldest and the most western unit is the ultramafic sequence. Towards the east, the komatiite unit has a sharp contact with a 2-5 m massive sulphide/breccia unit. This contact is the Calista shear. The stratigraphic sequence east of the Calista shear/massive sulphide unit consists of a series of basaltic units. This includes both massive and pillowed tholeiitic basalt, basaltic lithic lapilli tuff, and is interspersed with interflow sedimentary rocks. In the middle of this sequence lies the Orelia dolerite that has been classified as an ophitic basalt. Further towards the east the next unit is a felsic zone dominated by sandstones, siltstones and mudstones with intercalations of poorly sorted volcaniclastics tuffs of dacitic composition. This felsic unit is intruded by 2 dolerites, the Cumberland and then the Lotus dolerite. The whole Orelia stratigraphy is intruded by a suite of late intermediate dioritic to lamprophyric dykes ranging from 0.5 m to 2-3 m in width. The sequence appears to be upright with the older Ultramafic member thrusted over the basaltic and felsic units.The main host rocks of mineralisation at Orelia-Cockburn are deformed and altered tholeiitic basalts, and intermediate to felsic volcaniclastic rocks. It appears that the structures in the main mineralised corridors exploit the rheological contacts between the different units’ geological units.There are three main mineralised zones within the Archaean sequence, Orelia, Cumberland, and Calista.Calista has two styles of mineralisation. One is shear hosted within the massive sulphide breccia unit in the contact between the ultramafic unit and the basalt. The second is a stockwork of quartz-carbonate-sulphide veins within the basalt. Orelia mineralisation largely consists of a stockwork of quartz-carbonate-sulphide veins along the contacts of the Orelia dolerite and interflow sediment units that form a cigar/pipe like ore shoots.Cumberland also has two styles of mineralisation. The narrow high-grade mineralisation often presents as boudinage and inch and swell with quartz veins with minor sulphides. The low-grade mineralisation presents as a stockwork of quartz and quartz-carbonate veins related to the main veins.DimensionsThe Orelia Mineral Resource has an overall north-south strike, the mineralised corridor length is approximately 2,000 m. The overall mineralised width of Orelia ranges between 100 m and 400 m, the majority is approximately 200 m wide.Mineralized zones are variable with true width ranging from 0.5 m to 20 m. They are extensive along strike and down dip, raging 100 m up to 1000 m along strike in case of the Cumberland mineralisation. The down dip extends range form 50 m to 300 m. Some of the lode present cigar like shapes.Depth from surface is form 100 m up to 500 m approximately as the mineralisation plunges 30 degrees towards the south. The mineralised envelope has been extended down dip and long strike for targeting purposes any mineralisation modelled beyond the drilling coverage has not been included in the resource classification or reporting.
