The Pumpkin Hole undertaking is a high-grade iron-oxide copper-gold deposit situated south-east of Yerington, Nevada, US.
The mine is developed as each an open pit and an underground mine. It was found by US Metal in 1960 and bought by Nevada Copper in 2015.
Exploration has outlined 5 separate deposits to this point. Two high-grade deposits, designated East and E-2, are underground, whereas the remaining three, North; South; and South-East are open-pit deposits.
All state and country-level permits to start the event of underground entry have been granted in April 2011. The mine began underground manufacturing in December 2019 and has a projected mine lifetime of 13.5 years.
Nevada Copper introduced the submitting of a voluntary petition for reduction below Chapter 11 of the US Chapter Code in June 2024.
Pumpkin Hole mine location
The Pumpkin Hole property is located roughly seven miles (11.26km) south-east of Yerington, Nevada, inside Lyon County. The undertaking is situated within the Mason Valley, which runs north-south and lies between the Singatse and Wassuk mountain ranges.
Geology and mineralisation of Pumpkin Hole
The property is located on the japanese fringe of the Quaternary gravel-covered Mason Valley, and it contains a tertiary (Oligocene) tuffaceous volcanic meeting. This volcanic sequence contains quartz-latite ash flows and crystal tuffs, that are surmounted by the Singatse Tuff Formation, characterised by lithic-rich tuffs.
The southwestern phase of the Pumpkin Hole property is primarily characterised by Mesozoic strata from the early Jurassic, consisting of fine-grained felsitic siltstones and tuffs, that are in flip overlaid by thinly bedded carbonaceous, calcareous argillites, tuffs, and limestones.
The Jurassic Yerington Batholith intrusion has resulted in intensive IOCG (iron oxide copper gold) mineralisation, primarily skarn, which accommodates copper, magnetite, and ranging quantities of gold and silver. This skarn mineralisation is primarily situated within the center to decrease sections of the Gardnerville Formation, the higher a part of the Mason Valley Formation, and throughout the intrusive granitoid.
Reserves at Pumpkin Hole mine
The confirmed and possible reserves at Pumpkin Hole open-pit mine are estimated to be 385.7 million tonnes (mt) grading 0.47% of copper (Cu), as of January 2019. The overall contained copper is estimated at 3,590 million kilos (mlb).
The confirmed and possible reserves at Pumpkin Hole underground mine are estimated to be 23.9 mt (internet) grading 1.59% Cu.
Mining technique at Pumpkin Hole
The Pumpkin Hole property is developed utilizing each open pit and underground mining strategies.
The transverse long-hole stoping technique was chosen because the optimum mining approach for all three zones – EN, ES, and E2 – of the underground undertaking on account of security, mining restoration, dilution management, and productiveness concerns.
The stopes are 100ft excessive × 50ft extensive for the ES and E2 zones, and 75ft excessive × 50ft extensive for the EN zone.
Stopes are mined bottom-up to minimise lead time and upfront improvement. In narrower sections of the E2 zone, longitudinal long-hole stoping is used for better effectivity in lateral improvement.
The open-pit improvement contains two mining areas: the North Pit and the South Pit. Mining started within the higher-grade North Pit, adopted by the lower-grade South Pit. The North Pit is designed in 4 phases whereas the South Pit is designed in two phases.
Underground ore processing at Pumpkin Hole
The Pumpkin Hole copper underground ore concentrator is designed to course of 5,000 brief tons per day (stpd) of copper ore sourced from the East and E2 deposits.
The run-of-mine (ROM) ore undergoes crushing in a main jaw crusher earlier than being transferred to the grinding circuit. This circuit contains a semi-autogenous grinding (SAG) mill and a ball mill, which collectively facilitate a two-stage grinding course of inside a closed circuit that features a pebble crusher and classifying cyclones. The grinding happens as a moist course of.
The discharges from each the ball mill and the SAG mill converge into a typical cyclone feed hopper. From right here, the slurry is propelled to a cluster of cyclones. The overflow from these cyclones is directed into the rougher flotation conditioning tank, marking the graduation of the flotation course of. The pulp density of the slurry feeding the rougher flotation is persistently maintained at roughly 35percentw/w solids.
Within the rougher flotation circuit, the milled pulp is handled to get well the specified minerals. The ensuing rougher focus is floor additional after which handed via cleaner flotation to reinforce the focus to a marketable high quality. Subsequently, the flotation focus undergoes thickening, filtration, and storage in preparation for cargo.
Open-pit ore processing particulars
The Part I processing facility is designed to deal with 13.5mtpa and Part II provides capability for an additional 12mtpa.
In Phases I and II, ore from the North and South Pits is crushed on the pit crest by a single crusher. The crushed ore is transported through an overland conveyor to coarse ore stockpiles for every part, offering surge capability for feeding into the grinding circuits.
Ore is reclaimed from the stockpiles utilizing apron feeders and is discharged onto conveyor belts that feed the SAG mills. Each phases utilise a two-stage grinding circuit, with SAG mills in a closed circuit with pebble crushers and ball mills additionally in a closed circuit with hydrocyclones.
The ball mill and SAG mill each discharge into the frequent cyclone feed hopper, from which slurry is pumped to a cyclone cluster.
The milled pulp undergoes rougher flotation to get well goal minerals. The rougher focus is floor and processed via cleaner flotation to provide a high-grade copper focus. The ultimate focus is thickened, filtered, and saved earlier than cargo.
Web site infrastructure at Pumpkin Hole
The property is accessed through a sealed public street community to E Pursel Lane to inside 3.5 miles (5.6km) of the property.
A brand new 120kV transmission line is constructed from a service level on the present NV Power System to the mine web site.
Contemporary water is sourced from dewatering effectively WW-01.