In 2006, work completed on the Prominent Hill Project in the reporting period included drilling of 17 RC holes for 4,255 m and 46 mud/diamond holes at Prominent Hill prospect for 14,301.5 m. The drilling at Prominent Hill intersected wide zones of...
In 2006, work completed on the Prominent Hill Project in the reporting period included drilling of 17 RC holes for 4,255 m and 46 mud/diamond holes at Prominent Hill prospect for 14,301.5 m. The drilling at Prominent Hill intersected wide zones of copper-gold mineralised haematite breccias which enabled estimation of a JORC-compliant, global (Measured + Inferred + Indicated) resource of 119 Mt at 1.3% copper and 0.49g/t gold at a 0.3% copper cut-off. Other work included: Geotechnical drilling at Prominent Hill, regional diamond drilling at several prospect areas – 8 holes for 5250 m and mineralogical studies. A Bankable Feasibility Study on Prominent Hill was completed by mid-year and Mining Lease 6228 was granted on 2 August 2006. The Oxiana Board formally approved the development of the Prominent Hill copper-gold mine on 25 August 2006. A regional drilling program on EL 3056 saw 8 mud/diamond NQ2 holes drilled for 5250.7 m. Diamond drill holes were completed at Proteus, Neptune, Triton, Caliban and Prominent Hill East. The regional holes targeted gravity and magnetic geophysical features and interpreted structural zones. Whole-rock and trace element analyses were obtained for existing pulps to carry out a geochemical desktop study of the interpreted Gawler Range Volcanic-equivalent rocks at Prominent Hill and Neptune and a suite of metavolcanics intersected in the Danae Hill and Torch area, approximately 30km to the east. The study concluded that the metavolcanics from the Danae Hill area are geochemically distinct from the Gawler Range Volcanics. This metamorphosed bimodal suite most likely has an Archaean or Palaeoproterozoic age [see included report]. In 2007, exploration activities included drilling at Prominent Hill with the aim of increasing the confidence in the Cu-Au mineralisation zone along with a regional drilling program focused on EL 3056, targeting iron oxide copper gold (IOCG) style alteration and mineralisation. Further work has included the merger and validation of company databases (CRAE, NOREX, Minotaur and Oxiana), target generation, a PACE project proposal, a ground gravity survey over 7 prospect areas (1690 stations), open File gravity data compilation and merging with closed file data (the final dataset contained 67,462 observations), domain analysis using detailed geophysics and drillhole data, and downhole gamma probing of diamond drillholes. Oxiana completed a regional drilling program to explore for IOCG mineralisation in the vicinity of Prominent Hill. Eight rotary mud/diamond holes were drilled for 5728.1 m on EL 3056 at the Neptune, Proteus, Triton, Larissa, Taurus, and Blaze prospects. At Neptune DD07NEP005 intersected porphyritic, basaltic andesite lavas with hematite “red rock” and magnetite alteration. A narrow interval of supergene chalcocite was noted near the cover-basement interface. The best intervals returned 40m @ 0.22%Cu, 24m @ 0.17%Cu and 20m @ 0.12%Cu. Oxiana believe that the coincident magnetic and gravity anomalies of the prospect have been sufficiently tested and is downgraded for a 50+Mt orebody of >1% Cu. At Proteus drilling was in follow up to historical intersections of strong hematite alteration and bornite mineralisation at the key regional contact between amphibolite facies metamorphics to the north and GRV-equivalents to the south. DD07PRT002 intersected chloritic phyllite to 420 metres, followed by volcanics and intense earthy-steely hematite alteration in a fault zone. Low-grade results for Cu: 0.88 m @ 0.59% Cu from 499.12 m and 2 metres @ 0.20% Cu from 502 m, trace bornite was observed. Oxiana believe that the gravity high feature, along with the Metasediment – GRV contact appears to have been adequately tested. Drilling at Triton targeted a non-magnetic gravity anomaly in which previous drilling had intersected anomalous Au, Cu, Fe, U and REE. Hole D07TRI002 intersected numerous zones of low-grade Cu-Au, including a narrow zone of strong chalcopyrite mineralisation (5-10%) at 251 m and better intervals zones of Na-depletion, elevated U and REE (max. 129ppm U and 3600ppm Ce + La). Oxiana believe that more work is required at the prospect. The Larissa prospect is a gravity anomaly located proximal to Neptune and is located near the interpreted position of the key regional contact between metamorphics to the north and unmetamorphosed GRV-equivalents to the south. Two holes were drilled with hole DD07LAR001 intersected basaltic lavas that have a density of approx. 2.9g/cm3 which would explain the gravity high anomaly to an extent. DD07LAR002 was terminated in intermediate volcanics for a total depth of 710.7 m, some high SG values obtained but it is inconclusive as to whether they adequately explain the gravity anomaly. Taurus is a NW-trending coincident gravity anomaly and high amplitude magnetic anomaly NE of the White Hill area, interpreted as a fault splay containing abundant IOCG (magnetite-dominant) alteration. Taurus is one of the most significant magnetic features on the Project Area. Two holes were drilled into the southern end of the feature and intersected mafic and felsic intrusives including gabbro, granite, aplite, pegmatite as well as metsedimentary rocks such as graphitic schists, altered pelite, calc-silicate. Metasomatic magnetite-rich rock, and to a lesser extent magnetite-matrix breccia is also evident. DD07TUR001 contained intervals of abundant sulphide associated with magnetite replacement and veining. Assays returned broad Cu and Fe anomalism and narrow higher grade Cu mineralisation and Pd-Pt mineralisation. DD07TUR002 intersected highly altered mafic/ultra-mafic lithologies with magnetite alteration, containing anomalous to low-grade Pd-Pt values. The Pd-Pt intervals also contain very high Fe and anomalous Ni of 300-1000ppm. The nature and style of the Pd-Pt mineralisation is poorly constrained. The Blaze prospect target is alteration/mineralisation associated with a gravity and semi-coincident magnetic anomaly within a broad arcuate magnetic zone possibly related to the margin of an intrusive body, and to date had not been drilled sufficiently as to test the anomaly. Hole DD7BLZ005 intersected predominantly magnetite-albite-actinolite-quartz-diopside altered gneisses intruded by relatively unaltered granites and pegmatite and late massive calcite veins. Only one sample returned an anomalous result for Cu: 1.91 m @ 0.26% Cu from 398 m. Mo to 1200 ppm was also returned over 1.73 m. Further work at Blaze is unlikely at this stage.
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