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Location: 92 km E from Baguio, Philippines
Barangay Didipio, Nueva VizcayaKasibuPhilippines
Stay on top of the latest gold discoveries. Examine the latest updates on drilling outcomes spanning various commodities.
Mining scale, mining and mill throughput capaciites.Full profiles of select mines and projects.
Shaft depth, mining scale, backfill type and mill throughput data.Full profiles of select mines and projects.
Equipment type, model, size and quantity.Full profiles of select mines and projects.
Camp size, mine location and contacts.Full profiles of select mines and projects.
On May 13, 2024, OGC completed a secondary offering of 20% of its Philippine subsidiary, OceanaGold Philippines, Inc. (OGPI), through an Initial Public Offering (IPO) on the Philippine Stock Exchange (PSE), under the ticker ‘OGP’.
The listing fulfilled requirements of the renewed Financial or Technical Assistance Agreement (FTAA) with the Philippine government.
The Dinkidi Stock is an alkalic gold-copper porphyry system, NW-trending body that is roughly elliptical in shape at surface (480 m long by 180 m wide) and with a vertical pipe-like geometry that extends to at least 800 m below the surface.Porphyry-style mineralization is closely associated with a zone of K-feldspar alteration within a small composite porphyritic monzonite stock intruded into the main body of diorite (Dark Diorite). The extent of alteration is broadly marked by a prominent topographic feature (the Didipio Ridge) some 400 m long and rising steeply to about 100 m above an area of river flats and undulating ground. The northwestern end of the Didipio deposit is truncated by the Biak Shear. It is believed that the True Blue prospect is the displaced northern tip of the deposit.Didipio Deposit MineralizationThe Didipio copper-gold mineralization is associated with two main magmatic events, each accompanied by alteration and mineralization (Wolfe and Cooke, 2011). These magmatic events represent the evolution of the Didipio intrusive complex from a silica-undersaturated to a silicasaturated system.The silica-undersaturated mineralization is related to the intrusion of the Monzonite Porphyry and the Balut Dykes. The Monzonite Porphyry intrusion produced weak copper-gold mineralization accompanied by patchy pervasive orthoclase along the margins of the porphyry and biotitemagnetite alteration in the intruded rock. The copper-gold mineralization was further enhanced with the emplacement of the Balut Dykes causing calc-potassic alteration with Kfeldspar±actinolite-sulphide and diopside-perthite±actinolite-magnetite-sulphide veining. Bornite dominates the sulphide species of the veins and stockworks. The varied textures and composition of the Balut Dykes possibly heralds the onset of magma mixing and the shift to a more silica-saturated magma.With the emplacement of the succeeding syenitic porphyry intrusions (Feldspar Porphyry and Syenite), the system evolved to more silica-saturated. Quartz-sulphide veins began to form and were later hydrothermally brecciated to form a high-grade, quartz-dominated breccia (QBX) above the Syenite. Wall rock alteration consists of quartz-calcite-actinolite-sulphide and illitecalcite-sulphide. There is also a suggestion that the QBX is genetically related to the equally wellmineralized Balut Dykes (Sillitoe, 2017) which would imply that the QBX is co-genetic with the Balut Dykes and that it was emplaced prior to the intrusion of the Feldspar Porphyry and the Syenite.More recent underground exploration and development has discovered a pipe-like mineralized breccia body (called Eastern Breccia or EBX), east of the mine grid at level 2250 mRL and below. The breccia consists of two units, monzonite porphyry gradational to monzonite porphyry intrusion breccia, both intruded by a smaller cylindrical body of feldspar porphyry igneous breccia (Sillitoe, 2023). The breccia contains intergrown actinolite, apatite, calcite, magnetite, chalcopyrite and bornite. Some veinlets cut the breccia containing semi-massive chalcopyrite and bornite which give some high-grade Cu and Au values. The breccia pipe is probably related to the silica-saturated magmatic event.The deposit is oxidised from the surface to a depth between 15 m and 60 m, averaging 30 m. The oxide zone forms a blanket over the top of the deposit and largely comprises silicification, clay and carbonate minerals, accompanied by secondary copper minerals including malachite and chrysocolla. All of the oxide and transitional mineralization has been mined out since mining commenced in 2012.Description of DepositsThe Didipio Mineral Property is an alkalic porphyry copper-gold system (Jensen and Barton, 2000; Bissig & Cooke, 2014). Globally, alkalic deposits are relatively uncommon compared to calcalkaline porphyry copper deposits which occur the length of the main magmatic arcs known on the planet. Alkalic porphyry deposits are genetically associated with more spatially restricted alkaline volcano-plutonic geological provinces. The Didipio deposit exhibits features that are common to other alkalic porphyries found in British Columbia, Canada, and eastern Australia. The main features of this porphyry type are:• Alkalic porphyry intrusions are host to Au-Cu mineralization;• Generally associated with extensional tectonics and commonly occur in a back-arc setting;• The porphyry intrusion and associated mineralization tend to be small although higher grade and may contain appreciable gold and silver;• Presence of calc-potassic alteration consisting of orthoclase, magnetite, apatite perthite, and diopside is associated with the main stage Au-Cu mineralization;• Sulphur isotope compositions are characterized by negative sulphur isotope values consistent with oxidized magmatic sources of sulphur.
The Didipio open pit mine was completed to final design in May 2017 after five years of mining. The underground project commenced in March 2015 with the construction of the underground portal and has continued development since. Top-down longhole open stoping with pastefill is used throughout the mine.To facilitate the transition from open-pit mining to underground mining, a Crown Stabilisation Project (CSP) was initiated in 2017, whereby small amounts of material were mined from the pit floor before an engineered crown pillar consisting of cemented rock fill (CRF) were placed in the bottom of the pit to maintain stability and maximize recovery of ounces from the underground.The open-pit CRF activities total 101,927 m3 remaining to maintain a 25 m crown pillar above the Eastern crown stopes, with completion due in Q3 2026.The stoping front at Didipio is divided into three panels:• Panel 1: 2430 mRL to 2280 mRL;• Panel 2: 2250 mRL to 2100 mRL;• Panel 3: 2070 mRL to 1980 mRL.Mine DesignUnderground AccessAccess to the underground at Didipio is via a portal (Portal 1) from a bench in the upper open-pit. Portal 1 is the main travelway for personnel, materials and haulage equipment. A second portal (Portal 2) is located at the 2450 mRL on the southern side of the open-pit and provides fresh air for ventilation and secondary means of egress, with occasional use by some personnel and mobile equipment.Mining MethodDidipio employs a Long Hole Open Stoping mining method (LHOS) which is a commonly employed method suitable for steeply dipping orebodies. The method allows a high degree of mechanisation and offers good mining selectivity, good recovery and is relatively flexible to suit variable geometries and ground conditions. A transverse primary/secondary stoping sequence is predominantly used at Didipio. The sequence progresses from the top down beneath paste backfill, with personnel and equipment working on top of insitu rock (the exception to this is some stopes in the upper levels on the west of the orebody in the Breccia Zone that is discussed in further detail below).Primary stopes are mined first and are separated by secondary stopes. Extraction of the secondary stope can only occur after the two immediately adjacent primary stopes, and the stopes directly above in the crown, have been mined, pastefilled, and have had sufficient time to cure. The primary/secondary sequence employed at Didipio allows for stoping to be undertaken concurrently in multiple working areas, allowing for increased production rates compared to other methods such as longitudinal retreat.Productivities and Mine Production ScheduleThe Didipio underground schedule is based on productivity assumptions using a combination of historical rates achieved at Didipio and first principles based on expansion of the mine at depth and associated infrastructure that will facilitate an increase in throughput.The schedule was completed using Deswik mine planning software and is based on operations occurring 365 days/year, seven days/week, with two 12-hour shifts each day.PastefillPastefill is utilized at Didipio through the mixing of thickened tailings, water and binder. This process is essential for the management of regional stability and high recovery of the resource utilizing the top-down mining approach. Pastefill designs ensure structural strength to support the chosen mining method and mitigates liquefaction potential. The use of tailings material aids in reducing TSF emplacement and is considered in tailings volume calculations.The paste plant was commissioned in 2018 and delivers paste to underground stopes by a gravity distribution piping system. The paste plant sizing, based off earlier iterations of the LoM, was 150 m3 /hr at 60% utilization. Future pastefill requirements have increased in-line with planned increased production rates from the underground.
Primary CrushingThe crushing circuit is situated next to the ROM pad. Mining trucks haul ore from the open -pit stockpiles or from the underground portal to the ROM pad and dump on separate finger stockpiles to allow blend control. ROM ore is fed by a front-end loader (FEL) through an 800 mm square aperture static grizzly into a 100-tonne live capacity ROM bin. The FEL is required to remove oversize material retained by the static grizzly.The ROM ore is reclaimed from the ROM bin by an apron feeder and is discharged on to a static grizzly into a single toggle crusher. Fines will bypass the crusher. Static grizzly bars are set at a nominal 100 mm clearance.The single toggle crusher, selected to handle 900 mm maximum lump size, crushes the ROM ore to a typical P80 product size of 100 mm. An overhead travelling crane is provided for changing out crusher jaw plates and for maintenance on other adjacent equipment. Dust suppression water sprays are provided at the ROM bin and at the head of the transfer bin feed conveyor, emergency stockpile feed conveyor and SAG mill feed conveyor. The sprays can be automatically turned on/off from the plant control system.Primary and Secondary CrushingThe 7.3 m diameter by 4.57 m effective grinding length (EGL) SAG mill is fitted with steel liners and vortex discharge grate and pulp discharges. The SAG mill is equipped with a 4,300 kW wound rotor induction motor and Liquid Resistance Starter (LRS) and has capability to provide speed variation through a Slip Energy Recovery (SER) unit.Media charging is from 900 kg drums of 125 mm grinding balls via a kibble to the mill feed chute. A target ball charge of 13% is maintained with a media addition rate of 0.20 kg/tonne of feed. Mill load is determined from monitoring the hydrostatic pressure in the trunnion mill lube system. A rock sizing camera is installed on the SAG feed conveyor to monitor feed size distribution, and a vibration meter is placed at the outside shell of the SAG mill. The vibration meter or scanner can measure intensity/vibration energy, toe of the charge, and impacts (number of events whereby the ball is directly hitting the steel liner). The scanner gives live and accurate reading of the condition inside the mill. The integration of feed size, inside mill parameters (intensity, toe, and impact), mill weight, and SAG power is used to control the mill speed and feed rate.Discharge from the SAG mill flows through a rubber-lined trommel and into a common mill discharge hopper. Oversize from the trommel screen (scats) is directed to a Sandvik CH-440 pebble crusher through the scats recycle conveyor to reduce the scats size to -12 mm. A portion of the recirculating load (cyclone underflow) is fed back to the SAG mill to assist with the transfer of the scats out of the discharge end of the mill.The 5.5 m diameter by 8.38 m rubber-lined ball mill is fitted with a 4,300 kW wound rotor induction motor, LRS, trommel screen and retractable feed spout/chute. Discharge from the ball mill flows through a rubber-lined trommel into the common mill discharge hopper. The combined SAG and ball mill discharge is pumped to a nest of nineteen Cavex 15-inch hydro cyclones. The hydro cyclone underflow is split, with approximately 30% reporting to ball mill feed and 10% reporting to the SAG mill. The other 60% reports to an Outotec SK-500 Flash Flotation Rougher cell for recovery of the coarse liberated gold and copper particles. The concentrate from the Flash Flotation Rougher reports to a gravity circuit and the hydro cyclone overflow gravitates on to the flotation rougher circuit.The Flash Flotation Rougher utilizes a twin outlet design with the low-density top valve tailings reporting to the common mill discharge hopper to maintain ball mill density.
Recovery of copper and gold at Didipio is achieved from the use of a combination of flotation following a conventional SAG mill/ball mill grinding circuit and gravity gold recovery.The plant was successfully running and exceeding the 3.5 Mtpa nameplate since the 2014 processing plant upgrade, with a well-established workforce and management team in place until June 2019 when operations were suspended.Following renegotiation of the FTAA in July 2021, the plant was restarted in November 2021 with full production achieved by Q2 2022. An amendment to ECC in 2022 incorporated a processing rate limit increase from 3.5 Mtpa to 4.3 Mtpa. Process plant throughput was ramped up to 4 Mtpa by late 2022 and has been operating in the 4-4.1 Mtpa rate since with progressive debottlenecking studies undertaken to ramp up to the permit limit utilising stockpiled ore to fill capacity.Gravity CircuitThe purpose of the gravity circuit is to recover free gold from the mill discharge and flotation concentrate streams. The primary gravity circuit utilizes a Falcon SB2500 batch concentrator. A bypass option allows the Flash Flotation Rougher concentrate to bypass the concentrator and report directly to the Flash Flotation Cleaner when the concentrator is in a rinse cycle or is offline. Other gravity circuit components consist of a surge bin for the concentrate, a Gemini and a Deister table treating all the concentrate, and a further Falcon model SB250 concentrator on the table tails, all of which are located in the secured area of the gold room.The concentrate from the SB2500 concentrator unit gravitates to the gold room for further processing. The tailings from the concentrator reports to the Flash Flotation Cleaner TC-10 flotation cell where the coarse copper and gold particles are recovered with the concentrate, then report to the combined final concentrate hopper with the re-cleaner concentrate and pumped to the concentrate thickener. The tailings from the Flash Flotation Cleaner report to a hopper and are then pumped back to the combined mills discharge hopper to be pumped back to the cyclones.An additional Falcon SB750 batch concentrator was installed in November 2016 in the fine flotation circuit and was fully operational in February 2017. This gravity concentrator treats the Rougher concentrate stream prior to entering the Cleaner circuit. The concentrate from SB750 reports directly to the surge bin in the gold room while the tailing goes to the Cleaner circuit. A bypass option allows the Rougher concentrate to bypass the concentrator and report directly to the Cleaner circuit when the concentrator is in a rinse cycle or is offline.Flotation CircuitCyclone overflow reports by a gravity line to the first of six rougher flotation cells. Outotec TC-40 tank cells are used for the roughers with progressively increasing froth crowders installed down the train. Rougher concentrates are pumped to the Falcon SB750 fine gravity concentrator (GC003), while rougher tailings report to the flotation tailings hopper for pumping to the tailings thickener. Tails of the GC003 feed the cleaner bank, and its concentrate is discharged to the gold room.Concentrate from the cleaner cells feeds the bank of re-cleaner cells. Tailings from the re-cleaner cells mix with the GC003 tails as feed to the cleaner cells. Concentrate from the re-cleaner cells is directed to the final concentrate pump box and then transferred to the concentrate thickener. The tails from the cleaner cells feed into the cleaner-scavenger cells, while the tails from the last cleaner-scavenger cell report to the cleaner tails hopper, and then pumped back to the rougher feed bank. The concentrate from the cleaner/cleaner-scavenger cleaner cells can be fed to either the feed of the re-cleaner cells or the cleaner cells dependent on concentrate grade. The concentrate from the cleaner- scavenger cells report back to the feed of the cleaner cells. A control system called FrothSense was installed in 2016 to automatically control the operating parameters of the flotation cells. A Metso Courier 6 On Stream Analyzer monitors key flotation circuit streams continuously for copper, iron and solids concentrations. With the increasing proportion of underground ore in the processing feed, paste backfill contamination (consisting of 6-12% binder) occurs when mining secondary stopes and leads to increase in the natural pH of the flotation feed slurry. At times, slurry pH has exceeded 10 causing depression of gold bearing pyrite in the flotation circuit. Following laboratory testing and plant trial, a sulfuric acid dosing system was installed to control slurry pH to flotation to below 9.5 to ensure gold recovery is maximized from the recovery of pyrite to the flotation concentrate.Concentrate HandlingFinal concentrate is thickened in a 12 m diameter high-rate thickener fitted with a vane feed well and de-aeration tank. The underflow is pumped at about 60-70% solids to a pair of 450 m3 storage tanks. A Outotec PF-930 horizontal plate pressure filter press produces a concentrate filter cake at about 8% moisture, which is suitable for transport and sea freight to smelter customers. As part of the efforts to increase the annual throughput to 3.5 Mtpa, four additional plates were installed in the concentrate filter in 2014 to increase its capacity by 20% to a total of 26 plates. With the decreasing copper head grade in the underground ore and stockpiles compared to upper open-pit or the 4.3Mtpa milling rate requires less filtration capacity than is currently installed.The filter cake discharges to a concentrate stockpile of about 15 days capacity located within the concentrate storage shed. The concentrate is loaded into dump trucks using a front-end-loader with a nominal payload of 20 wet tonnes per truck. Composite samples are prepared from trucks as they are loaded, testing for moisture and metal content. A weighbridge weighs all trucks leaving site to account for movement, inventory control of material, and tracking for permit requirements.Concentrate is trucked by road to a storage shed located at Poro Point, La Union with the capacity to hold up to 15 kt of material. Ships are loaded periodically in 5.5 kt or 11 kt shipments. Turnaround time for the concentrate trucks averages 27-32 hours.Gravity Gold Concentrate TreatmentThe concentrates from the Falcon SB2500 and Falcon SB750 concentrators are screened with a Amkco Vibra-screen. The screen oversize product reports to the Gemini shaking table while the undersize product is treated using the Deister shaking table. Concentrate from the Falcon SB5200 concentrator are tabled separately on a Deister shaking table. Concentrates from the tables are filtered and dried prior to smelting in a standard diesel-fired barring furnace. The tailings and middling products from both table circuits are retreated in small Falcon SB250 concentrators, with the concentrate joining the Deister feed. The tailings from the combined SB2500/SB750 Falcon concentrators are returned to the final concentrate pump box to minimise any gold losses from the gravity cleaning circuit. Table tailings from the SB5200 circuit are pumped back to the mill discharge hopper.The dried gravity concentrates are mixed in batches with fluxes designed to allow the best separation of the gold and silver into doré. These batches are smelted and poured into molds to produce gold/silver doré bars, which typically assay 85% gold and up to 15% silver. Iron and base metal levels in the bars are typically less than 3%.
Raw water is currently sourced from the underground mine dewatering discharge water that has undergone solids removal via coagulant and flocculant addition, followed by flow through four settling ponds. Part of this discharge is from a pair of production bores located outside the completed open pit. These bores pump water to the mine dewatering tank which transfers water to the plant raw water tank for use in gland water systems, gravity and gold room operation, reagent mixing and potable water treatment. Raw water requirement is approximately 80 m3 /h. Process water is recovered from within the plant from the tailings and concentrate thickeners with makeup sourced from the TSF pond at 340m3 /h. Recycle rates of process water are high, exceeding 80% with the only raw water makeup into the system from services requiring higher quality water. The Paste Plant requires approximately 140m3 /h clean water supply for its operation. To supply this requirement, underground dewatering water is used. This is pumped through several stages of ponds intended for turbidity treatment before most of it is released to environment and part of it is directed to mine dewatering tank that supplies the Paste Plant.Since 2018, all water used in the processing plant is recycled, utilizing both the overflow water from thickeners and decantwater from the TSF tailings pond.
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