Deposit Type
- Epithermal
- Carlin-type
- Sediment-hosted
- Volcanic hosted
Summary:
Mineralization at MLP most closely resembles Carlin-type sediment-hosted gold systems of northern Nevada. The Mother Lode deposit model includes structurally and stratigraphically- controlled disseminated sulfide and oxide mineralization hosted in primarily in Tertiary sedimentary rocks and rhyolite porphyry dikes. Paleozoic sedimentary rocks comprise a smaller volume host in proximity to dikes and the basal Tertiary unconformity. Tertiary volcanic rocks and debris flow breccias are also mineralized at Mother Lode. Alteration types associated with gold mineralization include passive decalcification and illite-pyrite alteration. Unique features of Mother Lode-style mineralization compared to typical Carlin-type deposits include: the association with fluorine, the significant volume of mineralization that is rhyolite porphyry dikehosted, elevated tellurium and bismuth, and the generally passive, innocuous, very low-silica nature of the mineralization. Carlin-type gold deposits are generally known to form at depths of >2 kilometres, at temperatures between 180-240o C. Mineralization at Mother lode may have formed at depths of 500-1000 metres or less, and at temperatures <240o C (Weiss, 1996).
Gold mineralization in the main Bullfrog and North Bullfrog sub-districts is characterized as volcanic-hosted low-sulfidation epithermal type. Two styles of epithermal precious metal mineralization are present: 1) disseminated mineralization associated with sulfidation of iron in the volcanic host rocks; and 2) open-space filling quartz and/or carbonate veins, which are controlled by boiling. Pervasive quartz-adularia alteration of volcanic rocks is intimately associated with the disseminated mineralization and is an important ground preparation process for later vein forming events. Epithermal deposits form at shallow depth, from the surface to generally <2 kilometres. Temperatures of formation range between 150 to 300°C. Mineralization at NBP is typical of other low-sulfidation type gold systems in and around the Walker Lane trend such as: Bullfrog, Round Mountain, Rawhide, Aurora, Bodie and Comstock. These deposits commonly contain higher grade gold in vein and stockwork zones surrounded by zones of lower grade disseminated mineralization. This is the accepted exploration model at NBP.
Summary:
Conventional surface mining methods using surface drill and blast techniques with off highway haul trucks and front-end loaders will be employed at both the Mother Lode open pit and the North Bullfrog open pits. Higher grade mineralization from the YellowJacket vein and vein stockwork, and any Sierra Blanca sulfide mineralization with sufficient grade would be trucked on Highway 95 to a central mill facility located at Mother Lode.
In the conceptual mine plans, 10-metre-high benches would be drilled and blasted, then loaded into 133 tonne haul trucks using 20 cubic metre front end loaders. At NBP, the haul trucks would deliver the mineralized material to either the stockpile transfer system for the mill grade mineralization or place the blasted material directly on the leach pad. The stockpile transfer system would consist of a grizzly, a feeder and conveyor belt feeding bins. Highway haul trucks would be loaded from the bin and transport the mill grade mineralization to the MLP mill stockpiles using Highway 95. Mill grade mineralization from MLP would also be stockpiled at the mill location. Mining rates at both NBP and MLP are sufficient to create a mill stockpile that will allow higher grade mineralization to be fed (grade streaming) to the mill in early years of the schedule. The mill stockpile is scheduled to reach a maximum size of 11.7 M tonnes by the end of year 2, and then begin to decline through the LOM.
The mine plan calls for an average total mining rate of 66 million (“M”) tonnes per year of combined overburden and mineralized material. Of that, an average of 30 M tonnes per year would be mineralized material placed on a heap leach pad at an average rate of 82 k tonnes per day. Another 3 M tonnes per year would be delivered to the mill at an average of 8,200 tonnes per day. The average overburden to mineralized material (strip ratio) would be 1.08. Based on this mining rate, the Project would have an active life of 9 years, with minor gold production for the additional 3-year rinse down period on the leach pad.
Processing Technologies
- Gravity separation
- Flotation
- ROM/dump leach
- Counter current decantation (CCD)
- Concentrate leach
- Pressure oxidation
- Carbon in leach (CIL)
- Carbon in column (CIC)
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
The PROJECT Oxide materials will be processed in a standard heap leach recovery circuit commonly used in the region. The cyanide solutions from the heap leach will be treated in a Carbon-in-Columns (“CIC”) gold adsorption and desorption circuit.
The MLP mill will process NBP oxide, NBP sulphide and MLP sulphide materials separately from stockpiles. NBP Oxide material will be processed in a conventional gravity/CIL mill. Sulphide materials from both MLP and NBP will be processed through a milling and flotation plant to produce a concentrate. The flotation concentrate will be thickened, stockpiled, and processed through a pressure oxidation circuit followed by a CIL circuit. Oxide and sulphide CIL tails will be detoxified through an Inco/SO2 type process. Tailings will be pumped to a paste tailings thickener. Slurry will be deposited as a paste in a tailings facility. Detoxified, non-cyanide containing paste thickener overflow solution, will be returned to the mill.
Carbon from the CIC and CIL circuits will be processed in a carbon handling circuit located at the mill. The carbon handling will include carbon stripping, acid washing and reactivation circuits. The process solutions from carbon stripping will be sent to electrolytic cells for gold recovery in a precipitate sludge. The sludge will be retorted for mercury removal and then melted into doré bars in a furnace.
Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Gold
|
Recovery Rate, %
| 78 |
Gold
|
Head Grade, g/t
| ......  |
Silver
|
Head Grade, g/t
| 0.93 |
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Reserves at September 18, 2018:
Category | OreType | Tonnage | Commodity | Grade | Contained Metal |
Measured
|
Heap leach
|
34,560 kt
|
Gold
|
0.27 g/t
|
305 koz
|
Measured
|
Mill / Sulphide
|
9,311 kt
|
Gold
|
1.59 g/t
|
475 koz
|
Measured
|
Total
|
43,871 kt
|
Gold
|
0.55 g/t
|
780 koz
|
Measured
|
Heap leach
|
14,525 kt
|
Silver
|
1.41 g/t
|
658 koz
|
Measured
|
Mill / Sulphide
|
6,019 kt
|
Silver
|
11.47 g/t
|
2,220 koz
|
Measured
|
Total
|
20,544 kt
|
Silver
|
4.36 g/t
|
2,878 koz
|
Indicated
|
Heap leach
|
149,374 kt
|
Gold
|
0.24 g/t
|
1,150 koz
|
Indicated
|
Mill / Sulphide
|
18,249 kt
|
Gold
|
1.68 g/t
|
988 koz
|
Indicated
|
Total
|
167,623 kt
|
Gold
|
0.4 g/t
|
2,138 koz
|
Indicated
|
Heap leach
|
129,251 kt
|
Silver
|
0.66 g/t
|
2,758 koz
|
Indicated
|
Mill / Sulphide
|
8,315 kt
|
Silver
|
8.93 g/t
|
2,388 koz
|
Indicated
|
Total
|
137,566 kt
|
Silver
|
1.16 g/t
|
5,146 koz
|
Measured & Indicated
|
Heap leach
|
183,934 kt
|
Gold
|
0.25 g/t
|
1,455 koz
|
Measured & Indicated
|
Mill / Sulphide
|
27,560 kt
|
Gold
|
1.65 g/t
|
1,463 koz
|
Measured & Indicated
|
Total
|
211,494 kt
|
Gold
|
0.43 g/t
|
2,918 koz
|
Measured & Indicated
|
Heap leach
|
143,776 kt
|
Silver
|
0.74 g/t
|
3,416 koz
|
Measured & Indicated
|
Mill / Sulphide
|
14,334 kt
|
Silver
|
9.99 g/t
|
4,608 koz
|
Measured & Indicated
|
Total
|
158,110 kt
|
Silver
|
1.58 g/t
|
8,024 koz
|
Inferred
|
Heap leach
|
78,742 kt
|
Gold
|
0.26 g/t
|
549 koz
|
Inferred
|
Mill / Sulphide
|
2,284 kt
|
Gold
|
1.61 g/t
|
118 koz
|
Inferred
|
Total
|
81,026 kt
|
Gold
|
0.26 g/t
|
667 koz
|
Inferred
|
Heap leach
|
64,669 kt
|
Silver
|
0.48 g/t
|
1,008 koz
|
Inferred
|
Mill / Sulphide
|
116 kt
|
Silver
|
9.12 g/t
|
34 koz
|
Inferred
|
Total
|
64,785 kt
|
Silver
|
0.5 g/t
|
1,042 koz
|
Mine Management:
Job Title | Name | Profile | Ref. Date |
.......................
|
.......................
|
|
Feb 8, 2019
|
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Corporate Filings & Presentations:
Document | Year |
...................................
|
2018
|
...................................
|
2017
|
...................................
|
2016
|
- Subscription is required.
News:
News | Date |
Corvus Gold Expands Mother Lode Deposit Intersects New Deep Intrusive Zone Below Main Deposit with 50.3m @ 1.50 g/t Gold
|
December 5, 2019
|
Corvus Gold Makes New Vein System Discovery at Cat Hill, North Bullfrog Project, Nevada
|
October 23, 2019
|
Corvus Gold Inc. Closes C$23 Million Bought Deal Financing
|
October 10, 2019
|
Corvus Gold Inc. Announces C$20 Million Bought Deal Financing
|
October 2, 2019
|
Corvus Gold Ongoing Drill Program Continues to Expand Sierra Blanca Deposits to the West at North Bullfrog Project, Nevada
|
September 23, 2019
|
Corvus Gold Closes $1.3M Private Placement Financing with AngloGold Ashanti (USA) Inc. at $2.60 per Share
|
August 20, 2019
|
Corvus Gold Expands North Bullfrog’s Sierra Blanca Deposit to the West and North, Intersecting 16.8m @ 1.37 g/t Gold & 24.4m @ 1.21 g/t Gold and Stakes Land Package Adjacent to New Kinross Gold Claims
|
August 6, 2019
|
Corvus Gold Expands Mother Lode Deposit to the North, Intersecting 48.8m @ 1.15 g/t Gold & 36.6m @ 1.59 g/t Gold, Defines New Style of Gold-Silver Mineralization
|
June 11, 2019
|
Corvus Gold Expands Mother Lode Mineral Resource Potential to the West & Southwest, Drills 36.6m @ 2.03 g/t Gold & 25.9m @ 2.43 g/t Gold (including 18.3m @ 3.3 g/t)
|
June 3, 2019
|
Corvus Gold Signs Private Placement Financing and Alaskan Royalty Sale Totalling $1.25M with EMX Royalty
|
May 21, 2019
|
Corvus Gold: PEA Results for Combined North Bullfrog and Mother Lode Deposits, Nevada
|
November 1, 2018
|
- Subscription is required.