Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Heap leach
- Carbon in column (CIC)
- Elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
- Rotary kiln & Electric furnace
|
Mine Life | 7 years (as of Jan 1, 2018) |
The Gold Bar gold deposit is mined as four open pits: Gold Ridge (Ridge), Gold Pick (Pick) and two small pits at Cabin Creek (Cabin).
The Gold Pick, Gold Ridge and Cabin Creek deposits of the property are included in McEwen Mining's plans of open pit operations and the Gold Bar South deposit is now in the process of being added to the mining plan. |
Latest News | McEwen Mining: Updated Gold Bar Resource and Reserve Estimates January 7, 2021 |
Source:
Deposit Type
- Breccia pipe / Stockwork
- Carlin-type
- Sediment-hosted
Summary:
Central Nevada is underlain by Paleozoic sedimentary and volcanic rocks which were in turn covered by Tertiary volcanic rocks and sediments. During the early Paleozoic, this part of Nevada was the western pre- continental margin of the North American plate. From Silurian through Devonian time, extensive carbonate platforms developed along the continental margin, generating a thick wedge of carbonate sediments to the west as the basin subsided. Farther to the west in deep water, shale, chert and sandstone (siliciclastic rocks) were deposited during that time.
Within the Gold Bar North (GBN) area, three gold deposits have been defined: Gold Pick, Gold Ridge and Cabin Creek. Mineralization in Gold Pick has a strike length of over 4,000 ft with a width of 1,600 ft and thickness of 100 – 150 ft. Gold Ridge and Cabin Creek are ancillary deposits comprising together approximately 22% of the mineral resource. All defined mineralization lies within 500 ft of surface in oxidized carbonate host rocks.
There are two structural blocks in the district, separated by the regionally extensive RMT. Deep-water shale and chert, known as the Vinini Formation (upper plate) were pushed eastward onto the carbonates (lower plate) along the RMT. Late-Paleozoic clastic sedimentary rocks were deposited on both upper and lower plates. Younger (post-Permian) lowangle faulting locally placed lower plate rocks on top of both the upper and lower plates. Tertiary extension resulted in the complex basin and range high-angle block faulting that defines the range today.
SIGNIFICANT MINERALIZED ZONES
Gold Bar North
The Gold Pick, Gold Ridge and Cabin Creek deposits are found in the McColley Canyon Formation.
Mineralization is controlled both by stratigraphy and by overprinting structures. Much of the mineralization in all three deposits is at an orientation that mimics bedding and probably represents favorable permeability in certain debris flow subunits that were selectively more receptive to gold deposition. At Gold Pick East this bedding orientation is N50°E, 23°SE, at Gold Pick West it is N07°E, 24°E, at Gold Ridge it is N20°E, 20°SE and at Cabin Creek it is N01°E, 27°E.
Mineralization also tracks a strong northeast-southwest fabric that is supported by structures identified during surface mapping. These southwest-trending structures are at moderate to steep angles (45-70°NW). At Gold Pick East, the high-angle structures focus grade along on N245°E, 45-60°NW. At Gold Ridge, the orientation is N265°E, 70°NW. The highest gold grades in the deposit are concentrated along these structures likely at the intersection with low-angle stratiform mineralization.
All of the mineralization found to date at the GBN occurs as sediment-hosted, “Carlin-type” gold deposits. The deposits are hosted in carbonate-rich sedimentary rocks of the Devonian Nevada Formation and are characterized by micronsized gold and a distinct hydrothermal alteration suite.
If the term “Carlin-type gold deposits” is used in its strictest sense, the deposits are restricted to a small part of the North American Cordillera in northern Nevada and northwest Utah. Most such deposits are located along long-lived, deep crustal structures inherited from Late Proterozoic rifting and formation of a passive margin. They are hosted in a Paleozoic miogeoclinal carbonate sequence that is either structurally overlain by a eugeoclinal siliciclastic sequence (the Roberts Mountains Allochthon), or stratigraphically overlain by a miogeoclinal siliciclastic sequence deposited in the resulting foredeep (Overlap Assemblage). Gold mineralization is localized at intersections of a complex array of structures with permeable and reactive strata. Carbonate dissolution, argillization of silicates, sulfidation of ferroan minerals and silicification of limestone characterize alteration related to the main stage of mineralization. Gold is found as micron inclusions or solid solution in arsenian pyrite. Common trace elements are antimony, thallium and mercury.
Gold Bar South
The lower 100-200 ft of the overlying Mississippian Webb Formation (siltstone, mudstone), hosts the bulk of the GBS (Gold Bar South) gold mineralization.
The most economically prospective mineralization at GBS occurs at the crest of an east-tilted doubly plunging anticline, interpreted from consistent Devils Gate – Webb Formation contacts recorded in drill logs. Overall the anticline is tilted, with a steeper 25° dipping east limb and a flat west limb. The anticline plunges north at approximately 10° and plunges steeper to the south at approximately 20° before it is ultimately covered by deep basin-filling alluvium.
Mineralization occurred at the base of the Webb Formation and was subsequently offset by a series of east-side-downstepping northeast and northwest-trending normal faults. Mineralization is rarely preserved along these high-angle faults, though undoubtedly some of them served as conduits to fluid flow during the gold event. Locally, normal faulting has created small grabens, in which the thickness of mineralization appears to be enhanced. There is evidence, by reconstructing grade trends of some left- lateral oblique slip on northeast-trending faults, especially in the southern part of the deposit. Lastly, and similar to Gold Bar North, there appears to be some “ponding” of mineralization in troughs of the Devils Gate – Webb Formation contact. These are interpreted as potential karst dissolution zones or debris flows with enhanced permeability.
Gold mineralization at GBS was deposited in brecciated siltstones of the Webb Formation, at and immediately above its contact with the Devils Gate Limestone. Lesser, but important amounts of mineralization occur in the adjacent Devils Gate Limestone as well. Mineralization in GBS consists of epithermal, disseminated, sediment-hosted gold, in zones related to hydrothermal dissolution in limestone and the resulting collapse breccia in the overlying siliciclastic unit. Gold is associated with brecciated, oxidized, silicified, and argillized mudstones, siltstones, and sandstones of the Webb Formation and is usually accompanied by silicification and strong barite veining. Jasperoid along the trace of the fault is brecciated and contains veins of barite and scattered gold mineralization. In contrast to the sediment-hosted GBN deposits, GBS gold mineralization is associated with brecciation.
Approximate Depths and Extents of Gold Deposits in the Gold Bar Area:
Deposit - Gold Pick;
Depth Range - 0-500 ft;
Average Depth – 165 ft;
Strike Length - 4,000 ft;
Width - 1,650 ft;
Thickness – 150 ft.
Deposit - Gold Ridge;
Depth Range - 0-325 ft;
Average Depth – 115 ft;
Strike Length - 1,000 ft;
Width – 650 ft;
Thickness – 115 ft.
Deposit - Cabin Creek;
Depth Range - 0-325 ft;
Average Depth – 100 ft;
Strike Length - 1,000 ft;
Width – 1,300 ft;
Thickness – 115 ft.
Deposit - Gold Bar South;
Depth Range - 0-700 ft;
Average Depth – 350 ft;
Strike Length - 3,100 ft;
Width – 550 ft;
Thickness – 60 ft.
Summary:
The Gold Bar is planned for production using conventional hard rock open pit mining methods.
The Gold Bar is mined by a contractor. Contractor equipment on hand is often variable. There is flexibility in the fleet size and the actual mining fleet will likely vary depending on the contractor’s fleet on hand. The schedule and production requirements were based on 20 ft benches and the following fleet assumptions:
- Drilling will be completed with a dual sized drill fleet.
- Most of the waste is planned to be drilled with two rotary blast hole rigs with 60,000 lb pull down capacity and 6.75 in diameter blast holes.
- The ore zones are planned to be drilled with two percussion drills sized with a 3.5 in diameter blast hole.
- The blasted rock will be loaded into 100-ton haul trucks using three 15 cu yd front end loaders.
To date, mining at Gold Bar has been from three pits, two at Cabin Creek and one at Gold Pick West. The recent transition from the Cabin Creek pits to Gold Pick West has resulted in lower ore tonnes, gold grades and contained ounces from the upper benches of the pit as compared to block model. This observed disparity may be the result of greater structural control of the mineralization than was previously expected but is now visible in the newly-developed pit. With this recent information in mind, company is evaluating the model and the related mine plan with the third-party engineers retained by us to prepare the reserve estimate.
Overall Pit Slopes
Area – Pick:
Location – Central;
Max Interramp Slope Angle (degrees) – 54;
Bench Face Angle (degrees) – 70;
Bench Height (feet) – 60;
Berm Width (feet) – 22.
Area – Creek:
Location – East;
Max Interramp Slope Angle (degrees) – 54;
Bench Face Angle (degrees) – 70;
Bench Height (feet) – 60;
Berm Width (feet) – 22.
Area – Ridge:
Location – West;
Max Interramp Slope Angle (degrees) – 42;
Bench Face Angle (degrees) – 60;
Bench Height (feet) – 60;
Berm Width (feet) – 32.
Three mining areas were designed for the Gold Bar project with approximately 300 ft of operating width on each bench within a phase. The phases are designed to accommodate two-way haulage for a 100-ton haul fleet.
The following criteria were applied to the final pit and phase designs:
- Haul Road Width 85 feet
- Haul Road Grade 10% Maximum
- Operating width between pushbacks 200-300 feet nominal.
Processing will involve ore passing through a single stage of crushing, which will allow for belt conveyor stacking of the ore onto a heap leach pad. The new heap leach pad has been located and designed with expandability for an ore reserve increase.
The crushing, agglomeration, and stacking circuits are designed for 480 dry short tons per hour (stph), with operations scheduled for 24 hours per day, seven days per week, 350 days per year. At an expected 70% operating availability, this will result in placing an average of 8,057 stpd onto the heap leach pad, equivalent to 2,820,000 tons per year.
Run-of-mine (ROM) ore will be trucked from the mine to a stockpile close to the primary crusher and subsequently reclaimed with a front-end loader (FEL). The FEL will dump ore into a surge bin. A vibrating grizzly feeder will draw ore from the surge bin, with the feeder oversize reporting to a jaw crusher. The grizzly feeder undersize material will bypass the crusher and will combine with the crusher product on the primary discharge belt conveyor.
The grizzly undersize and the primary crushed ore will be conveyed to a vibrating, inclined screen. Screen oversize will bypass the agglomeration drum and report to the screening discharge belt conveyor. The undersize fraction from the screen will be conveyed to the agglomeration drum for the binding process. Cement and barren solution will be added on the screen undersize conveyor ahead of the drum. Agglomerated ore will combine with the screen oversize on the screening discharge belt conveyor. The agglomeration drum and all downstream material handling equipment are physically located within the containment of the heap leach pad liner system.
Crushed and agglomerated ore will be transferred to an overland conveyor. The screening discharge conveyor, which receives the agglomerated ore and screen oversize (+3 inch), transfers material onto the stacking feed conveyor. The stacking feed conveyor discharges onto a series of several mobile ramp conveyors and mobile grasshopper-type conveyors. Units of mobile conveyors and grasshopper-type conveyors will be added or removed as required, dependent upon the stacking location on the pad. The final conveyor will be a radial-type mobile stacker that will place agglomerated ore in lifts, up to 25 feet in height. As multiple lifts are placed, the edges of the heap will be concurrently reclaimed to a 3:1 slope. This will reduce closure costs and facilitate safer and easier leaching of the slopes.
Processing
- Heap leach
- Carbon in column (CIC)
- Elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
- Rotary kiln & Electric furnace
Flow Sheet:
Summary:
Gold and silver are extracted from mineralized material by either milling or heap leaching depending on, among other things, the amount of gold and silver contained in the material, whether the material is naturally oxidized or not, and the amenability of the material to treatment.
At the Gold Bar mine, precious metal recovery is through conventional heap leaching and adsorption, desorption, regeneration (ADR) technology for metal extraction from crushed and agglomerated ore.
HEAP LEACH PAD DESIGN
The heap leach pad is designed to be constructed in two phases (Phases 1A and 1B) with 4 cells each, for a total of 8 cells. The leach pad and process facilities extend from an elevation of 6,750 ft amsl at the toe of the process ponds to an elevation of 6,980 ft amsl at the northwestern edge of the leach pad perimeter road. The grade of the lined base receiving ore will range from 7 to 8% on the western half and 2 to 4% on the eastern half. In total, the leach ........

Recoveries & Grades:
Commodity | Parameter | 2019 |
Gold
|
Head Grade, g/t
| 0.81 |
Production:
Commodity | Units | 2019 |
Gold
|
oz
| ......  |
Gold Equivalent
|
oz
| ......  |
Silver
|
oz
| ......  |
All production numbers are expressed as metal in doré.
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Operational Metrics:
Metrics | 2019 |
Ore tonnes mined
| ......  |
Tonnes processed
| ......  |
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Reserves at December 31, 2018:
Resources and Reserves were updated as of December 31, 2018. Company will plan to revise estimate of Resources and Reserves at Q4 2020.
Category | Tonnage | Commodity | Grade | Contained Metal | Recoverable Metal |
Proven
|
2,411 k tons
|
Gold
|
0.037 oz/ton
|
88 koz
|
72 koz
|
Probable
|
15,725 k tons
|
Gold
|
0.028 oz/ton
|
436 koz
|
357 koz
|
Proven & Probable
|
18,136 k tons
|
Gold
|
0.029 oz/ton
|
524 koz
|
430 koz
|
Measured & Indicated
|
30,374 k tons
|
Gold
|
0.027 oz/ton
|
819 koz
|
|
Inferred
|
7,583 k tons
|
Gold
|
0.027 oz/ton
|
201 koz
|
|
Commodity Production Costs:
| Commodity | Units | 2019 |
Cash costs (sold)
|
Gold Equivalent
|
USD
|
......
|
All-in sustaining costs (sold)
|
Gold Equivalent
|
USD
|
......
|
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Financials:
| Units | 2019 |
Capital expenditures
|
M USD
| ......  |
Revenue
|
M USD
| ......  |
Gross profit
|
M USD
| ......  |
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Aerial view:
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