Geological l Aspects of the Prominent Hill Feasibility Study

Transcription

1 St Barbara s Day SA Explorers Conference Geological l Aspects of the Prominent Hill Feasibility Study DAVID WALLACE OXIANA LIMITED December 2005

2 Prominent Hill Best Copper- Gold Discovery of the Decade Discovered by Minotaur Resources in 2001 Oxiana earn-in from August 2003 Exploration success 66m at 2.54% Cu, 0.43g/t Au 135m at 1.48% Cu, 0.28g/t Au 129m at 1.31% Cu, 0.47g/t Au First Resource Announcement Aug 2004 PFS commenced Sept 2004 Oxiana Minotaur merger Feb 2005 July 05 Resource Upgraded PFS complete August 2005 BFS commenced September 2005

3 Prominent Hill Resource Base & Contained Metal RESOURCE BASE STYLE CATEGORY TONNES Cu Au Mt % g/t Cu/Au Breccia Indicated Inferred TOTAL Au Only Indicated Inferred TOTAL CONTAINED METAL STYLE COPPER Mt GOLD Mozs Cu/Au Breccia Au Only TOTAL Key Points Contained copper metal inventory maintained at a high level of confidence. Contained gold inventory increased by 1.2 million ounces through increased grade in Cu/Au Breccia and inclusion of Gold Only style mineralisation.

4 Prominent Hill Mineralogical Domains Cu/Au Breccia domained by copper mineralogy relating to different metallurgical characteristics DOMAIN Tonnes Tonnes % Cu % Au g/t 1 Chalcocite/Bornite 55,100, Chalcopyrite/Pyrite 24,100, Chalcopyrite/Bornite 15,100, Other 6,600,

5 Prominent Hill Tectonic Setting Chronology of Events (1-8): 1. Syn-basinal faulting. Graben development. 2. Open folding of volcanosedimentary sequence? (not shown on section). 3-8 Package is overprinted by an array of E-W and ESE trending faults of the mineralising PH event (red). S PROMINENT HILL FAULT DUPLEX N The parent fault (HFZ) causes the formation of a jog zone in the PH Fault Duplex. The dip of the faults in the duplex are reversed against the parent fault. Progressive faulting (3-8) each successive fault causes a smoothing of the jog zone. The magnetite skarn package is up-faulted along the northern margin of the HFZ. Current Erosional Surface VOLCANOSEDIMENTARY SEQUENCE GRV EXTRUSIVES GRANITE + SKARN PACKAGE 1km HILTABA INTRUSIVES

6 Prominent Hill Deposit Geology Prominent Hill is a Mesoproterozoic Fe Oxide-Cu-Au (IOCG) Deposit. Blind deposit: Covered by metres of Late Palaeozoic (Permian) and Mesozoic (Cretaceous) flat-lying sediments. Haematite-dominated. Closest analogy is Olympic Dam,? Carapateena. The PH sequence comprises, from south to north ( footwall to hangingwall ): 1. Mafic to intermediate volcanic units (GRV-equivalent) 2. Volcaniclastic sediments (sandstone siltstone), 3. Intermediate granitoid (brecciated quartz diorite, probable Hiltaba-equivalent) 4. Dolomitic carbonates, volcanic dykes or sills HANGINGWALL FAULT ZONE Skarn + Intermediate Granitoid + Chlorite-matrix breccia Cu-Au Host Sequence Package is cut by late (post-mineralization) dolerite dykes Gairdner dykes, ca.800 Ma The host sequence rocks are intensely altered by haematite + sericite ± quartz (hydrolytic alteration) Mineralization is hosted by haematite-matrix hydrothermal breccias within the host sequence.

7 Prominent Hill Geology Section 5500E WESTERN GOLD ONLY ZONE Cover Sediments High grade intersections include: DP g/t Au Prominent Hill Shear Zone D g/t Au 11.6 g/t Au Sediments Skarn / Granitoid Gold g/t < 0.5g/t 0.5 to 2g/t BD1 >= 2g/t Hanging wall Cu (LHS) and Au (RHS) Histograms Fault Zone Solid Geology Interpretation Gawler Range Volcanics m Scale 1 : 2000 Dolomite

8 Prominent Hill Geology Section 5900E CU/ AU BRECCIA ZONE Cover Sediments Main breccia zone remains open at depth below 9500RL BD1 Skarn / Granitoid Copper % Gold g/t < 0.3% < 0.5g/t 0.3 to 2% 0.5 to 2g/t >= 2% >= 2 g/t Cu (LHS) and Au (RHS) Histograms Solid Geology Interpretation BD2 BG2 Dolomite PH Shear Zone m Scale 1 : 2000 Gawler Range Volcanics

9 Prominent Hill Geology Section 6100E EASTERN GOLD ONLY ZONE Cover Sediments Gold Only Resource 1.2g/t Au Further ut drilling required ed off section to raise resource from inferred to indicated. Gold g/t < 0.5g/t 0.5 to 2g/t >= 2 g/t Gawler Range Volcanics Haematite- Silica Breccia BG3 Hangingwall Fault Zone Skarn /Granitoid Cu (LHS) and Au (RHS) Histograms Solid Geology Interpretation t ti m Scale 1 : 2000 Sediments BD3 PH Shear Zone

10 Prominent Hill Host Unit: Footwall Volcanic Strongly Altered Haematite + quartz altered vesicular lava (basalt or andesite?) with earthy haematite alteration selvedge. Quartz infilling vesicles. Minor disseminated bornite ± chalcocite replacement in amygdales.

11 Prominent Hill Host Units: Quartz - Sericite Greywacke Medium to coarse grained quartz greywacke with early micro-faulted quartz-haematite veins (containing lamellae of crystalline haematite) and later 2D array of haematite veinlets. Common as clasts within haematite matrix breccias. Central and western domains.

12 Prominent Hill Haematite -?diorite Rubble Breccia Weakly layered, poorly sorted with sub-rounded clasts of volcanic or intrusive. 4% fine-grained chalcopyrite mineralisation, possibly replacive in matrix and clasts.

13 Prominent Hill Milled Haematite Matrix Breccia Contains abundant spherical aggregates of pyrite, minor chalcopyrite and bornite. Minor bornite has replaced pyrite. Clasts are minor to absent. They have been pulverized and incorporated into the matrix.

14 Prominent Hill Mineralisation Styles Copper Gold 1. Disseminated, haematitematrix breccia hosted copper mineralization. 2. Massive chalcocite + haematite (intergrown) } stockwork in dolomite. 1. Haematite-matrix breccia hosted gold mineralization (0.2 to 2g/t level). 1. High grade gold mineralization in haematite-quartz breccia (0.5 to 10g/t Au) inferred resources. 2. High grade gold associated with carbonate and haematite veinlets in dolomite host (3 to 100g/tAu) not included in current resource. }

15 Prominent Hill Host Sequence: Dolomite Type 2 Dolomitic carbonate rock with pervasive earthy haematite alteration. Characteristically has a network of 1) early haematitic veinlets 2) late carbonate veinlets + coarse Au. Haematite altered dolomite NEVER contains high Cu, even where brecciated Leached of Cu? Is earthy haematite supergene?? Remobilized Au??

16 Prominent Hill North of HWFZ Chlorite Matrix Breccia Chlorite matrix breccia with haematite + K-feldspar + sericite altered granitic clasts and lesser clasts of quartzose metasediment. Also minor pyrite > chalcopyrite mineralization, trace fluorite. Low grade Cu only.

17 Prominent Hill North of HWFZ Magnetite Skarn Magnetite phlogopite - pyrite (tremolite-carbonate-serpentine-talc) skarn. Intersected t in Normandy and Burmine drill holes. Late carbonate + pyrite + fluorite + chalcopyrite veins. Low grade Cu, ~0.1 to 0.2% Cu

18 Prominent Hill Arckaringa Basin Stock Water Supplies Have demonstrated that sourcing water from the Boorthana Formation will not draw down stock water from the nonartesian Eromanga aquifer. Stuart Range Formation good aquitard. PROMINENT HILL MINE PROJECT ILL T Project Water Supply WELLFIELD DAVENPORT RANGE Saline lake systems Saline lake systems Billa Kalina Fault System Billa Kalina fault system Observation wells monitored during pump testing of Boorthana aquifer. Ground Water Dependant Ecosystems (Mound Springs) Basin architecture shows basement high separating artesian GAB (Great Artesian Basin) aquifers from the Boorthana aquifer. Water chemistry shows no mixing between GAB aquifers and Boorthana aquifers. Monitoring of mound springs will be required during production pumping Groundwater Moving from north and west Quaternary and Tertiary Sediments Bulldog Shale (aquitard) Eromanga Basin aquifers Stuart Range Formation (aquitard) Boorthana Formation (aquifer) Basement rocks Subartesian (confined) Boorthana Formation aquifer Artesian GAB aquifers Watertable (unconfined) Billa Kalina sub-basin aquifers Sub-artesian (confined) Boorthana Formation aquifer Artesian GAB aquifer discharge Billa Kalina sub-basin aquifers and Arckaringa Basin flow and discharge GAB springs Production well

19 Prominent Hill Initial Open Pit Initially open pit Pit size: 1.4km x 1.2km x 510m deep Ore mined: 8Mt/a Average Strip Ratio: 6.25 : 1 Stage 1 mine life: 9 years N Potential for further staged development Underground Larger pit E

20 Prominent Hill On Track for 2008 Initial Drilling Pre-feasibility Final Feasibility Final Assessment & Approvals Construction Commissioning Toda ay Late 2006 d Half nd Production Permitting

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