OTTAWA, ONTARIO -- (Marketwire) -- 03/27/13 -- Orezone Gold Corporation (TSX: ORE) is pleased to provide an update on the progress of the ongoing Feasibility Study, resource update and the latest drilling results for its wholly owned Bombore Gold Project in Burkina Faso, West Africa.
Highlights
-- Mining and processing costs for the oxide material have been reduced as
compared to those costs used in the August 2012 resource estimation. The
improvement in costs is based on the technical studies and current
design criterion for an oxide-only carbon-in-leach (CIL) plant. This
will have a positive impact on the next resource update and the
potential economics of the project.
-- Geotechnical work confirms that the pit slopes used in the previous
resource update were conservative and steeper slopes can be used and
should result in a positive impact on the next resource update and
feasibility study pit designs. No significant issues were discovered
with respect to ground water, infrastructure design, mine water
management or waste management.
-- Metallurgical studies indicate that previously estimated recoveries,
work indices and rapid leaching kinetics were reasonable. Further
optimization work including a gravity circuit, flotation and air
sparging with the addition of lead nitrate will be performed on the
sulphide material. Tests also indicate that approximately 67% of the
softer near surface saprolite oxide material (approx. 43% of the Aug.
2012 oxide resource) is amenable to using a scrubber as part of the
crushing/grinding circuit to send the already fine material directly to
the leaching circuit and thereby possibly reducing capital and operating
costs for an initial oxide-only CIL processing plant.
-- Drill results continue to indicate the potential to further expand the
oxide and sulphide resources.
Pit Slope Study
Golder Associates from Montreal, Quebec, delivered their final pit slope recommendations in a Technical memorandum that was received on March 14, 2013 and can be found on the Company website. Except for instances where the saprolite slope height would exceed 60 m, the pit slopes recommended by Golder are steeper than those used in the August 2012 resource estimation, i.e. between 36 and 55 degrees in saprolite (vs. 35 in 2012), 40 and 45 degrees in saprock (vs. 40 in 2012) and 45 and 55 degrees in fresh (sulphide) rock (vs. 45 in 2012). The final report is expected in Q2 2013.
Geotechnical Studies
Golder Associates from Montreal, Quebec, has essentially completed the field investigations and the laboratory test work that is required for the geotechnical design of the main infrastructure, the mine waste and potential construction material geochemical characterization and the water management plan. Golder will now focus on the engineering design and a feasibility design report that is expected in the following months.
Metallurgical Study
Orezone submitted a suite of 76 samples representative of Bombore oxide, sulphide and mixed gold-bearing material to McLelland Laboratories from Sparks, Nevada in October 2011 and their final report can be found on Orezone's website. The testing program was conducted under the technical direction of Mr. Jeffrey Woods, consulting metallurgist with the objective to determine ore variability and optimum conditions for cyanide leaching of the Bombore gold-bearing material. Each of the samples was submitted for detailed head analysis to characterize the samples by grade, cyanide solubility, elemental make-up and carbon and sulphide content. The majority of the samples were then combined into four different composites that represented medium grade oxide, high grade oxide, medium grade sulphide and high grade sulphide material. Metallurgical testing of the composite samples included gravity concentration, bulk sulphide flotation, direct agitated (bottle-roll) cyanidation, combined gravity concentration/cyanidation, bulk mechanically agitated CIL and carbon-in-pulp (CIP) cyanidation tests. A petrographic study, comminution tests and solid-liquid separation (SLS) tests were also conducted at third party laboratories.
The main conclusions of the McLelland Metallurgical report are:
- Gold recovery rates were generally rapid;
- Almost all variability samples were amenable to whole ore milling cyanidation treatment at optimized conditions;
- Conventional SO2/air tailings slurry treatment was effective in decreasing slurry CNWAD concentration to acceptable level;
- The optimum feed size for whole ore cyanidation of oxide composites was in the range of 100% -212um to 100% -150um;
- The optimum cyanide concentration for cyanidation of oxide composites was a maximum of 0.5 gNaCN/L (the lowest concentration used for this optimization work and could leave room for improvement);
- The optimum feed size for whole ore cyanidation of sulphide composites was 80% -53um;
- The optimum cyanide concentration for cyanidation of sulphide composites was 0.5 to 1.0 gNaCN/L;
- Gravity concentration prior to cyanidation may improve gold recovery for sulphide composites; and
- The sulphide composites responded well to flotation treatment for recovery of gold.
The main recommendations of the McLelland Metallurgical report are:
- Further optimization of the cyanide concentration for the oxide composites as gold recovery was not decreased at the lowest cyanide concentration tested (0.5 gNaCN/L);
- Further optimization of flotation conditions for the sulphide composites since they showed high gold recoveries by flotation;
- Further optimization of gold recovery for sulphide composites during agitated cyanidation testing should include air sparging and lead nitrate addition; and
- Mineralogical analysis of the tailings from outlier variability results may determine the causes for the few below trend recoveries.
Since December 2012, Orezone initiated the following complementary metallurgical studies
- Hazen Research Inc. from Golden, Colorado, has completed semiautogenous grinding (SAG) Mill Comminution (SMC) testing on three saprolite and saprock granodiorite PQ core samples. Their report was received on February 26, 2013 and is posted on the Orezone website.
- Orezone submitted a suite of 26 sulphide samples to SGS Laboratories from Lakefield, Ontario for additional comminution work including JK tech Drop Weight, Crusher Work Index and Bond Ball Mill Work Index test work. Their report is expected in Q2 2013. Preliminary results confirm the findings of previous similar studies by AMMTEC from Perth, Australia and McLelland on Bombore samples, indicating a Bond Ball Mill Work Index of 15 kWh/t for typical sulphide samples.
- Orezone submitted a suite of pyrrhotite-bearing sulphide samples to COREM from Quebec City, Quebec, for lead nitrate optimization tests, with the possible benefits of improving cyanidation recoveries and reducing cyanide consumption for this type of material. Their report is expected in Q2 2013.
- Orezone, with the supervision of G Mining from Montreal, Quebec, completed preliminary scrubbing tests on site which confirmed the potential use of scrubbers in a lower CAPEX\OPEX comminution circuit. Orezone then submitted a suite of eight oxide composite PQ drill samples to Met-Solve Laboratories Inc., from Langley, British Colombia, for scrubber test work and design parameters. The Met-Solve preliminary results are positive and indicate a scrubber is viable to process the upper and mid portions of the saprolite (softer portions). The final report of results and any suggested design parameters is expected in Q2 2013. Orezone plans to visit in April another gold operation in West Africa that uses a scrubber, with similar grades and resources to Bombore.
- Orezone has contracted Roche Ltd. from Montreal, Quebec, as the process engineers to deliver the preliminary mill design.
Resource Update
The Company has recently commissioned with SRK from Toronto, Ontario and G Mining an interim resource update using 68,400 m (843 holes) of the current program that will bring the total database to over 405,000 m (5,106 holes), including 72 recent P16 holes totalling 4,867 m. The update is expected to be completed in April 2013 and will be the basis for the reserves and the mine plan of the full Feasibility Study ("FS") to be released in 2H 2013.
Table 1 2013 Resource Update Optimization parameters
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Optimization Parameter Unit 2013 CIL 2012 CIL 2011 CIL
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Gold Price $/oz 1,400.00 1,400.00 1,000.00
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Govt. Royalty $/oz 70.00 70.00 40.00
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Selling Costs $/oz 2.5 2.5 2.5
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Dilution % 5 5 5
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Mining Loss % 5 5 5
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Overall Pit Slopes
Oxide Degrees 36(1) 35 35
Transition Degrees 44(2) 40 40
Fresh Degrees 51(3) 45 45
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Process recovery
Oxide % 92.0(4) 94.0 93.0
Transition % 89.0(5) 92.0 92.0
Fresh % 81.7(6) 82.0 81.0
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Mining Costs - Ore
Oxide $/tonne 1.74 1.90 1.40
Transition $/tonne 2.32 2.35 1.74
Fresh $/tonne 2.44 2.44 1.89
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Mining Costs - Waste
Oxide $/tonne 1.63 1.90 1.40
Transition $/tonne 2.18 2.35 1.74
Fresh $/tonne 2.28 2.44 1.89
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Incr. Bench Cost
per 10 m Bench $/tonne 0.03 0.04 0.03
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Processing Costs (7)
Oxide $/tonne 6.60 7.21 6.67
Transition $/tonne 7.83 9.76 8.52
Fresh $/tonne 15.02 12.66 12.43
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G&A Costs (8)
Oxide $/tonne 3.72 3.84 2.69
Transition $/tonne 3.72 3.84 2.69
Fresh $/tonne 3.72 3.84 2.69
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Notes:
(1),(2),(3) Average slopes were used for the 2013 Whittle optimization but
Golder's detailed recommendations will be used for the pit design; between
36 and 55 degrees for saprolite (where the height of the saprolite wall is
less than 80 meters), between 40 and 45 degrees for transition, and between
45 and 55 degrees for sulphide/fresh.
(4),(5),(6) For the 2013 Whittle optimization, this table shows the
metallurgical recovery expected around the average in-situ grade, and is
including fine carbon and solution losses of 0.017 gpt.
(7) 2013 Whittle optimization costs include $0.10/t in re-handling costs.
(8) 2013 Whittle optimization costs include $0.60/t of rehabilitation and
sustaining capital provisions. Ore haulage costs will be refined for each
pit in the feasibility study.
Exploration and definition drilling
The recent drilling has further expanded the southern P16 and the P17N deposits and with open ended mineralization, more expansion drilling is warranted. Scout drilling on the new P13 target on 400 m line spacing has intersected narrow mineralized zones on all fences in the northern portion of the target area; follow up reverse circulation (RC) and core (DD) drilling is required to confirm the geometry and the continuity of the mineralized zones intercepted during the scout drilling program. Results for this release include 7,734 m of RC drilling (151 holes) and 145 m of DD drilling (1 hole) and are essentially from the southern area of the property. The drilling in this location was designed to upgrade and expand the P16, P17N and Siga South deposits, as well as test new targets with limited to no prior drilling. Grades from P16, P17N and P13 remain higher than the average Bombore grade.
Drilling stopped at the end of February (drill rig moved to Orezone's Bondi project) and is expected to resume in April with one core rig and one RC rig until the end of June when the rainy season and two month break is planned.
An additional 92,000 m of results have now been released since the August 2012 resource estimation. The ongoing drill program continues to demonstrate the potential to upgrade and expand the resources, especially the softer near surface oxide resources. The current resource is constrained within optimized open pit shells that span 11 km and includes 4.13 Moz of measured and indicated (125 Mt @ 1.03 g/t) and 1.03 Moz of inferred resources (35 Mt @ 1.00 g/t) with an average depth of drilling to only 120 meters. The oxide portion of the resource occurs in the top 50 m and includes 1.76 Moz M&I and 0.26 Moz Inferred resources.
Table 2 Cumulative Results Excluded from the August 2012 Resource Reported to Date
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Total Drilling to Date Grade g/t
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Zone # of Holes Total m Uncut Cut(9)
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KT - RC 23 1,169 1.31 1.22
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CFU - RC 17 1,455 0.82 0.82
CFU - DD 16 2,517 2.72 1.08
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Maga - RC 268 17,885 1.09 0.96
Maga - DD 60 12,874 1.29 1.09
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P8P9 - RC 30 1,665 0.91 0.90
P8P9 - DD 44 8,416 1.04 0.99
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P11 - RC 22 1,100 1.29 1.11
P11- DD 4 641 1.66 1.14
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Siga E - RC 57 3,036 1.14 0.94
Siga E - DD 16 2,047 1.38 1.03
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Siga W - RC 35 1,750 0.89 0.89
Siga W - DD 17 2,127 0.93 0.88
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Siga S - RC 240 12,017 0.96 0.88
Siga S - DD 36 5,423 0.94 0.90
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P16 - RC 53 2,664 1.04 1.04
P16 - DD 10 2,032 1.41 1.28
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P17 - RC 4 175 2.43 2.25
P17 - DD 1 175 3.60 2.48
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P17 N - RC 51 2,598 1.09 1.04
P17 N - DD 1 175 0.72 0.72
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P17 S - DD 15 1,694 2.94 2.46
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P13 102 5,375 1.13 1.11
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North - RC 338 22,174 1.08 0.96
North - DD 120 23,807 1.29 1.04
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South - RC 354 17,903 0.99 0.90
South- DD 73 10,238 1.01 0.92
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SE - RC 57 2,839 1.14 1.13
SE - DD 11 2,207 1.53 1.34
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New targets - RC 153 7,973 1.11 1.07
New targets - DD 16 1,869 2.86 2.39
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All - RC 902 50,889 1.05 0.96
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All - DD 220 38,120 1.25 1.05
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Notes:
(9) Weighted average grade of individual assays, cut to 5 g/t.
Table 3 Breakdown of Drilling Meterage for this Release
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Zone Core Drilling RC Drilling
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# of holes Total m # of holes Total m
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P11 1 145 0 0
Siga South 0 0 63 3,140
P16 0 0 20 1,005
P17N 0 0 13 683
P13 0 0 51 2,705
Sterilization 0 0 4 201
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TOTAL 1 145 151 7,734
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Table 4 Highlights of Reverse Circulation Drilling Results for this Release
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Uncut Cut
From To Length Grade Grade Total
Zone Section Hole (m) (m) (m) (g/t)(10) (g/t)(11) Assay(12)
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P13 3400 TYC0038 25.00 32.00 7.00 1.57 1.57
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P13 2200 TYC0013 18.00 33.00 15.00 1.42 1.38
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P16 44225 BBC4008 29.00 43.00 14.00 1.05 1.05
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P16 43925 BBC4004 30.00 37.00 7.00 1.64 1.64
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P17 N 45975 BBC3989 36.00 57.00 21.00 0.83 0.83
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P17 N 45950 BBC3950 25.00 38.00 13.00 0.86 0.86
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P17 N 45950 BBC3951 12.00 19.00 7.00 1.60 1.60
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P17 N 45875 BBC3992 6.00 15.00 9.00 1.58 1.58
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Siga S 10650 BBC4072 30.00 42.00 12.00 4.08 2.40 Pending
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Siga S 9950 BBC4043 19.00 40.00 21.00 0.81 0.81 Pending
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Siga S 9900 BBC4036 10.00 32.00 22.00 0.69 0.69 Pending
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Siga S 9900 BBC4037 25.00 36.00 11.00 1.01 1.01 Pending
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Siga S 9750 BBC4025 39.00 50.00 11.00 1.25 1.25
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Siga S 9750 BBC4026 15.00 26.00 11.00 1.54 1.54
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Notes:
(10) Weighted average grade of uncut individual assays
(11) Weighted average grade of individual assays cut to 5 g/t
(12) Composite width and grade are preliminary where leach residue fire
assay results are pending
The mineralized intervals are based on a lower cut-off grade of 0.5 g/t, a minimal width of 3 m and up to a maximum of two consecutive meters of dilution being included. The true width of the mineralization is approximately 85% of the drill length intervals in KT, CFU, Maga, P16, P17 and P8P9 areas, and 95% of the drill length intervals in the Siga area. The true width is not known yet on P17N, P17S and P13.The half-core samples were collected by Orezone employees using a diamond saw. The core samples were prepared by SGS Burkina Faso s.a.r.l. at the Bombore site facility and then split by Orezone to 1 kg using Rotary Sample Dividers (RSDs). A 1 kg aliquot was analyzed for leachable gold at BIGS Global Burkina s.a.r.l in Ouagadougou, by bottle-roll cyanidation using a LeachWell™ catalyst.
The RC drilling samples were divided by Orezone employees using RSDs. A 2 kg split was prepared by SGS Burkina Faso s.a.r.l. at the Bombore site facility and then split by Orezone to 1 kg using RSDs. A 1 kg aliquot was analyzed for leachable gold at BIGS Global Burkina s.a.r.l in Ouagadougou, by bottle-roll cyanidation using a LeachWell™ catalyst. The leach residues from all samples with a leach grade in excess of 0.2 g/t were prepared by BIGS Global Burkina s.a.r.l. and then split by Orezone to 50 g using RSDs. A 50 g aliquot was analyzed by fire assay at SGS Burkina Faso s.a.r.l.. Orezone employs a rigorous Quality Control Program (QCP) including a minimum of 10% standards, blanks and duplicates.
Qualified Persons
The drilling program was executed under the supervision of Pascal Marquis, SVP Exploration for Orezone; the report titled "Report on Metallurgical Testing - Bombore Drill Core Samples, MLI Job No. 3625" was prepared by J. Davis, Metallurgist and Project Manager at McLelland Laboratories; the technical memorandum titled "Pit Slope Design for Bombore Project" was prepared by P. Frechette, Project Manager at Golder Associates and; the Whittle optimization parameters have been established by R. Gourde, Study Manager at G Mining Services Inc. All are Qualified Persons under National Instrument 43-101 and approved their respective technical information in this release.
About Orezone Gold Corporation
Orezone is a Canadian company with a gold discovery track record of +12 Moz and recent mine development experience in Burkina Faso, West Africa. The company owns a 100% interest in Bombore which is situated 85 km east of the capital city, adjacent to an international highway. Mineral resources are constrained within optimized open pit shells that span 11 km, and include 4.13 Moz of measured and indicated (125 Mt @ 1.03 g/t) and 1.03 Moz of inferred resources (35 Mt @ 1.00 g/t) with an average depth of drilling to only 120 meters. The Company is working to further expand the resources at Bombore while it completes a FS for a phase one oxide-only CIL plant in 2H 2013 and becomes a mid-tier gold producer by 2015.
FORWARD-LOOKING STATEMENTS AND FORWARD-LOOKING INFORMATION: This news release contains certain "forward-looking statements" within the meaning of applicable Canadian securities laws. Forward-looking statements and forward-looking information are frequently characterized by words such as "plan", "expect", "project", "intend", "believe", "anticipate", "estimate", "potential", "possible" and other similar words, or statements that certain events or conditions "may", "will", "could", or "should" occur. Forward-looking statements in this release include statements regarding, among others; ground water; infrastructure design; mine water management or waste management; scrubber and grinding circuit design; improvements in the project economics; optimization and trade-off studies; capital and operating cost estimates; gold production for the project; completion of technical reports in Q2 2013; completion of a resource update in April 2013; completion of a FS in 2H 2013; commencement of production at the Bombore Project in 2015.
FORWARD-LOOKING STATEMENTS are based on certain assumptions, the opinions and estimates of management at the date the statements are made, and are subject to a variety of risks and uncertainties and other factors that could cause actual events or results to differ materially from those projected in the forward-looking statements. These factors include the inherent risks involved in the exploration and development of mineral properties, the uncertainties involved in interpreting drilling results and other geological and geotechnical data, fluctuating metal prices, the possibility of project cost overruns or unanticipated costs and expenses, the ability of contracted parties (including laboratories and drill companies to provide services as contracted); uncertainties relating to the availability and costs of financing needed in the future and other factors. The Company undertakes no obligation to update forward-looking statements if circumstances or management's estimates or opinions should change. The reader is cautioned not to place undue reliance on forward-looking statements. Comparisons between any resource model or estimates with the subsequent drill results are preliminary in nature and should not be relied upon as potential qualified changes to any future resource updates or estimates.
Readers are advised that National Instrument 43-101 of the Canadian Securities Administrators requires that each category of mineral reserves and mineral resources be reported separately. Readers should refer to the annual information form of Orezone for the year ended December 31, 2011 and other continuous disclosure documents filed by Orezone since January 1, 2012 available at www.sedar.com, for this detailed information, which is subject to the qualifications and notes set forth therein.
Contacts:
Orezone
Ron Little
CEO
(613) 241-3699 or Toll Free: (888) 673-0663
rlittle@orezone.com
Orezone
Pascal Marquis
SVP Exploration
(613) 241-3699 or Toll Free: (888) 673-0663
pmarquis@orezone.com
