Orezone Gold Chas reported the summary results of an updated independent Feasibility Study (FS) for its 90%-owned Bomboré Gold Project in Burkina Faso, West Africa.
Image: The gold mineral. Photo: courtesy of carlos aguilar/Freeimages.com.
All reported figures are in U.S. dollars and are on a 100% project basis unless otherwise stated.
The FS envisions a shallow, free-dig open pit mining operation with a simple processing circuit consisting of a single stage grinding ball mill followed by a seven-stage carbon-in-leach (“CIL”) and standard Zadra gold recovery circuit. Tailings will be stored in a HDPE-lined facility that will be constructed in several stages over LOM from compacted mine waste, resulting in a smaller environmental footprint and improved costs.
“The robust FS results clearly demonstrate that Bomboré is a compelling project. The project’s favourable location, soft and shallow free-digging ore, simple flowsheet, modest power demand, and rapid leaching kinetics contribute to its low capital intensity and top-tier per tonne operating costs. Its modest upfront capital will also allow Orezone to advance directly into construction,” said Patrick Downey, President and CEO of Orezone. “With a strong treasury, we plan to commence with the Resettlement Action Plan (“RAP”) and detailed engineering in Q3 2018 followed by main project construction in Q2 2019. Furthermore, we see several opportunities to enhance value and increase LOM gold production, and we will advance these during the detailed engineering phase. Bomboré is one of the largest and most advanced undeveloped gold deposits in the region and has a very large free-milling sulphide resource directly beneath the oxide deposit that forms the basis of the FS. The Company plans to complete a detailed review of this sulphide resource in light of the excellent recent high grade drill results from the P17S zone with the aim of expanding the circuit to process higher grade sulphide zones as supplemental ore feed.”
BASE CASE SUMMARY
The Base Case assumptions include mineral reserves determined using an average gold price of $1,250/oz and revenues based on $1,275/oz. Capital estimates are based on quotes including taxes and freight received up to Q2 2018 from potential equipment and service providers. The thirteen-year operational plan is designed to bring forward a significant amount of gold production and cashflows by delivering higher grade ore in the early years with lower grade ore stockpiled and processed in the final two years of operations. However, based on a first stage review by the FS engineering consultants, the addition of one CIL tank and minor modifications to the remainder of the circuit could allow annual throughput to increase from the current design level of 4.5M tonnes per annum (“tpa”) to 5.2M tpa, enhancing Bomboré’s annual gold production profile as further described in the “Project Opportunities” section below.
Pre-production capital costs include the construction of a large water storage system and completion of all RAP activities. Previous studies envisioned a three-stage RAP program with only Stage 1 in the pre-production years.
Sustaining capital is estimated at $58.9 million consisting mainly of tailings dam construction. Replacement of process plant equipment will be minimal due to the projected low abrasion by the oxide material and all mining fleet replacement will be undertaken by the mining contractor. Reclamation and closure costs are estimated at $14.5 million.
The FS was completed by Lycopodium Minerals Canada Ltd. (“Lycopodium”) of Toronto, Canada (Process Engineering and Overall Study Manager), Knight Piésold and Co. of Denver, USA (Tailings and Water Storage Systems), AMC Consultants (“AMC”) of Vancouver, Canada and Maidenhead, United Kingdom (Reserves and Mining) and WSP Canada Inc. (“WSP”) of Montreal, Canada in conjunction with SOCREGE and BEGE of Burkina Faso (Social & Environmental).
Mineral Resource and Mineral Reserve
The Mineral Reserve estimate for the FS was prepared by AMC and is based on the January 5, 2017 Mineral Resource estimate prepared by RPA Inc. (“RPA”) of Toronto, Canada which includes 218.1 Mt of Measured and Indicated resources grading 0.68 g/t for 4.8 Moz plus 48.2 Mt of Inferred resources grading 0.64 g/t for 1.0 Moz. The mineral reserves used in the FS are limited to the Measured and Indicated near-surface saprolite and upper transitional resources to an average depth of 45 metres.
The Mineral Resource estimate consists of three separate block models:
The North model, which consists of the Maga, CFU, OCR, and P8P9 zones.
The South model, which consists of the P11, Siga E, and Siga W zones.
The Southeast model, which is to the south and southeast of the South model and consists of the P16 and P17 zones.
For the Mineral Reserve estimate, AMC developed new reserve block models, for each of the three resource block models, by applying the modifying factors necessary for conversion of Mineral Resources to Mineral Reserves. Those factors included amongst others, weathering profiles, mine cost centers, mining dilution and extraction factors, and pit slope angles. Cut-off grade (“CoG”) determinations for block assignments (ore versus waste) were based on a gold price of $1,250/oz.
Mine Plan and Processing Summary
The FS mine plan is based on an annual feed rate to the plant of 4.5M tpa of ore and delivering relatively higher-grade ore in the early years of the project. This results in building 6.1Mt of low grade stockpiles prior to Year 1 with further stockpile additions in Years 1 through 3 and subsequent drawdowns in the later years of operations. Over 80% of mine waste will be utilized as construction material for the tailings storage facility, thereby reducing water management costs and closure costs associated with waste dumps. The ore is free-digging with the oxides composed of over 70% passing 150 micron material that requires minimal grinding before leaching. The upper transition, although relatively soft, will require some grinding to achieve expected recoveries. The ball mill is sized to take a blend of 70% oxide/30% upper transition material. The current mine plan does not anticipate such a high percentage of transition material in the mill feed thus providing extra grinding capacity should a plant expansion be considered. Estimated gold ounces produced and diluted head grades for each year are summarized in the table below. An estimated 24,526 ounces of gold are recovered during the planned two-month commissioning period. During years 12 to 13, only lower-grade stockpiles are processed.
Mine Plan
The Company worked with AMC to develop a mine plan and production schedule (based on the January 5, 2017 resource model) which have been optimized to maximize project returns by processing the higher grade ore in the early years and stockpiling the lower grade ore for processing after mining is completed in Year 11. Initial head grades for Years 1 through 3 average 1.00 g/t, with Years 1 through 7 averaging 0.78 g/t. Mining will be by local contractor(s) using a conventional diesel-hydraulic excavator fleet, and small 30t and 50t road type rear-dump units as the ore and waste are all free-dig with little or no oversize material expected. This type of load and haul fleet is common in Burkina Faso and West Africa for similar free-dig material and will provide increased versatility as the mine plan consists of a large number of shallow pits of varying tonnage.
Total ore processed, including the lower grade stockpiles, will be 56.0 Mt grading an average of 0.64 g/t. The LOM strip ratio is approximately 1.68:1.
Mineral Processing
Significant metallurgical testing has been completed over several years which formed the basis of the Bomboré Project Study, with the most recent grinding and reagent optimization work completed at SGS in Quebec in Q4 2017. Lycopodium have reviewed the historical and recent test work data, and based the process flowsheet on this work.
The flowsheet and plant have been designed to process the soft fine-grained ore which eliminated the need for a crushing plant ahead of the grinding circuit. The ore is direct dumped across a static grizzly into a large hopper and on to a variable speed apron feeder. The system is designed to break any sticky, lumpy product that may be expected in the rainy season. From the apron feeder, the ore is transferred to a conveyor that feeds directly to the ball mill. The plant is designed with two ore transfer points and one conveyor, thereby eliminating potential issues associated with wet sticky ore in the rainy season. The ball mill is equipped with a variable speed drive sized to accommodate a wide range of ore types and hardness.
Ball mill discharge is pumped to a set of cyclones with the oversize reporting back to the mill and the undersize fed to a seven-stage CIL circuit for gold recovery. The CIL tails are thickened to recover process water and then pumped to a HDPE-lined tailings facility. The tailings facility is designed to be zero discharge, with water recovered in a decant tower and returned to the process water tank at the plant. Gold is recovered in a standard carbon desorption plant, finishing with electrowinning and smelting to produce gold doré bars.
Project Infrastructure
The project benefits from a mining-friendly jurisdiction, a strong mining culture, and excellent local infrastructure. Burkina Faso has experienced rapid development of its mining sector over the past decade which has contributed to the growth of available mining contractors, suppliers, and skilled labour. In addition, the project is favourably situated only 85 kilometres from the capital city of Ouagadougou, accessed off a 5 kilometre dirt road via the main sealed highway (RN4) that runs between the capital and the coast.
Offices and Accommodation
Orezone have already constructed a 76-bed camp which will be augmented by a new 18-bed private room accommodation block for senior staff. A fully functioning kitchen and dining facility are in place operated by a catering and accommodation service provider. A camp contractor will continue to be responsible for all operations at the accommodation camp including catering, cleaning and maintenance activities.
All offices and communication systems are in place and will require minimal upgrading.
Power Supply
A heavy-fuel oil (“HFO”) power station will be constructed at the process plant by an independent power provider (“IPP”) under a build-own-operate (“BOO”) agreement. The power station will be fitted with 7 x 1.6MW heavy duty HFO generator engines (or similar) with five operating and two standby units.
11 kV aerial transmission lines will be constructed from the power station to the tailings storage facility, waste storage facility, accommodation camp, and the mining contractor’s area.
The power station will utilize a dedicated bulk HFO storage facility located adjacent to the power house.
Water Supply
Raw water will be sourced from the seasonal Nobsin River and diverted by a permanent weir into an off-channel reservoir (“OCR”). The OCR is essentially one of the mine pits excavated early and designed to hold sufficient water for the project on an annual basis.
Pumps will transfer water from the OCR to the raw and process water tanks by HDPE pipeline.
Sustaining capital costs were estimated on the basis of quotes from potential providers. The closure and reclamation plan includes work to be conducted from the closure of the mine at the end of operating activities. The goal is to return the site to a satisfactory state as quickly as possible in terms of reducing the risks for health and safety, controlling erosion and developing a profile compatible with the future uses of the site.
Development Timetable
Estimated time to construct the Bomboré operation (pre-production) is 24 months, including time to excavate the OCR, complete the RAP, and commission the process plant equipment. The critical path items are the RAP and OCR excavation. Timely completion of the RAP will allow early commencement of the OCR excavation which will meet the water needs for commissioning, start-up and subsequent operations as the OCR is filled during the rainy season each year from May through October.
Permitting
The Bomboré project is fully permitted and ready for construction and operation. All necessary Environmental Baseline Studies were completed prior to submission of the Mining Permit application in 2015. The Mining Permit was granted on December 30, 2016 and remains in full force and effect.
Project Opportunities
Several opportunities exist for further improvements with the key ones being as follows:
The addition of one CIL tank and associated equipment could increase the processing rate to 5.2M tpa from 4.5M tpa. This change would increase production capacity and reduce the need for low-grade stockpiling and re-handle. This modification would increase annual production, particularly in the latter years of mine life, reduce LOM operating costs, and potentially improve project economics. The grinding circuit has been reviewed by Lycopodium and would not require any upgrades for this additional tonnage of oxide ore. Minor upgrades may be required to other ancillary equipment and services and these will be fully reviewed and costed during the early stages of detailed engineering.
Reduction of waste rock storage areas now provides more “real estate” to optimize the design of the tailings storage facility by reducing the overall height of the dam. A first stage trade-off between height and area by the engineers has indicated that this option may reduce sustaining capital through the LOM. Again, this trade-off will be fully investigated in the early stages of detailed engineering.
Mineralization is known to continue through areas of seasonal river flows which has been excluded from the Company’s current Mineral Resource and Mineral Reserve estimates. Orezone has performed studies in these “Restricted Zones” with WSP to examine potential mining procedures to allow for seasonal mining and concurrent final reclamation of these areas without significant impact to the environment. These plans were presented to the Ministry in charge of Environment which subsequently approved the ESIA process, and the Company is now advancing towards final approval to mine this mineralization and for inclusion in future Mineral Resource updates.
Recent drilling on the P17S target (see Orezone’s press release dated February 22, 2018) has indicated the potential to develop this area into a higher-grade shallow sulphide zone. Furthermore, there are several zones of high grade sulphides beneath the existing oxides. Orezone plans to review all data and if warranted will release a scoping study on the potential to mine and feed higher grade sulphides into the existing circuit using a small stand-alone crushing plant ahead of the ball mill.
Conversion of inferred resources to measured and indicated within the current mining permit area.
Regional drilling has indicated that oxide mineralization is present outside of the mining permit area on the surrounding exploration permits. The Company plans to continue exploration in these areas.
Technical Report Filing
Full details of the FS in the form of a National Instrument (“NI”) 43-101 technical report will be filed on SEDAR within the next 45 days. The Company is also in the process of updating the 2017 Mineral Resource estimate to include the drilling of several identified shallow high-grade shoots during 2017 and the mineralization in the Restricted Zones. A mineral resource update will be completed by Q4 2018.
Source: Company Press Release