Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Cut & Fill
- Longhole stoping
- Drift & Fill
- Cemented paste backfill
- Cemented rockfill
- Unconsolidated rockfill
|
Production Start | ... |
Mine Life | 2037 |
Hecla’s Greens Creek Mine in southeast Alaska is one of the largest and lowest-cost primary silver mines in the world. |
Source:
p. 46,47,180,180
Company | Interest | Ownership |
Hecla Juneau Mining Company
(operator)
|
12.52 %
|
Direct
|
Hecla Alaska LLC
(operator)
|
29.73 %
|
Direct
|
Hecla Greens Creek Mining Company
(operator)
|
57.75 %
|
Direct
|
Hecla Mining Company
|
100 %
|
Indirect
|
Greens Creek mine is owned by Hecla Mining through wholly owned subsidiaries. Greens Creek Mine is owned and operated pursuant to the Greens Creek Joint Venture Agreement by Hecla Greens Creek Mining Company (57,75%), Hecla Alaska LLC (29.73%) and Hecla Juneau Mining Company (12.52%).
Contractors
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Summary:
The Greens Creek deposit is a volcanogenic massive sulfide deposit with a relatively high precious metal content compared to other deposits of its type. The host rock consists predominantly of marine sedimentary and mafic to ultramafic volcanic and plutonic rocks, which have been subjected to multiple periods of deformation. These deformational episodes imposed intense tectonic fabrics and folds within the rock. The deposits occur at the contact between Mississippian-age mafic meta-volcanic footwall and a hanging wall of Triassic-age argillite and basalt. Extensive hydrothermal alteration occurred within the meta-volcanic footwall prior to and during ore deposition, converting the basalts to sericite-rich, phyllitic schist. At ore deposition, thick and extensive lenses of base and precious metals, with pyrite and barite, formed at the footwall-hanging wall contact. Major sulfide minerals include pyrite, sphalerite, galena, and tetrahedrite/tennantite.
Work by Taylor and Johnson (2010) in the USGS Professional Paper 1763 indicated that the Greens Creek deposit displays a range of syngenetic, diagenetic, and epigenetic features that are typical of volcanic massive sulfide deposits (VMS), sedimentary exhalative (SEDEX), and Mississippi Valley-type (MVT) genetic models. Based on those observations the investigators indicated that the Greens Creek mineral deposit was a ‘hybrid’ type with elements of several deposit models.
Due to variations in mineralization ........
Mining Methods
- Cut & Fill
- Longhole stoping
- Drift & Fill
- Cemented paste backfill
- Cemented rockfill
- Unconsolidated rockfill
Summary:
Greens Creek is a portal accessed mine that utilizes conventional rubber-tired mining equipment, and drill and blast techniques. Production mining is primarily executed using cut and fill and drift and fill methods, supplemented by longhole stoping where orebody geometry permits.
The orebody is complex which has resulted in each of the nine mining zones being unique in size and shape. Each requires differing levels of mine development infrastructure which is included in the mine plan. Ore handling is performed with a fleet of underground haulage trucks and scoop trams or load-haul-dump units (LHDs). Waste is either trucked out of the mine to the waste disposal area or is placed in previously mined-out stopes when available. All LHDs are equipped with remote operating capability and can be operated from an operations room on surface. Production areas are backfilled with either paste fill, created from concentrator tailings, or cemented or uncemented rock depending on future strength requirements.
Fresh air is fed into the mine via the 920 level access portal and distributed through a series of internal ramps and raises, and exhausts through the 1350 level portal and the 2853 surface raise. A ventilation on demand (VOD) system is currently in place in a limited number of headings and is planned to be extended to the remainder of the mine.
The LOM plan is based on a 2,300 stpd production rate continuing through to the end of mine life in 2035. Or ........
Source:
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Flow Sheet:
Summary:
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Source:
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Reserves at December 31, 2023:
The reserve NSR cut-off values for Greens Creek are $230/ton for all zones except the Gallagher Zone at $235/ton.
The resource NSR cut-off values for Greens Creek are $230/ton for all zones except the Gallagher Zone at $235/ton.
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
9 k tons
|
Silver
|
11.3 oz/ton
|
100 koz
|
Proven
|
9 k tons
|
Gold
|
0.08 oz/ton
|
1 koz
|
Proven
|
9 k tons
|
Lead
|
3.5 %
|
310 tons
|
Proven
|
9 k tons
|
Zinc
|
8.4 %
|
740 tons
|
Probable
|
10,009 k tons
|
Silver
|
10.5 oz/ton
|
105,122 koz
|
Probable
|
10,009 k tons
|
Gold
|
0.09 oz/ton
|
880 koz
|
Probable
|
10,009 k tons
|
Lead
|
2.5 %
|
250,270 tons
|
Probable
|
10,009 k tons
|
Zinc
|
6.6 %
|
657,990 tons
|
Proven & Probable
|
10,018 k tons
|
Silver
|
10.5 oz/ton
|
105,222 koz
|
Proven & Probable
|
10,018 k tons
|
Gold
|
0.09 oz/ton
|
881 koz
|
Proven & Probable
|
10,018 k tons
|
Lead
|
2.5 %
|
250,580 tons
|
Proven & Probable
|
10,018 k tons
|
Zinc
|
6.6 %
|
658,730 tons
|
Indicated
|
8,040 k tons
|
Silver
|
13.9 oz/ton
|
111,526 koz
|
Indicated
|
8,040 k tons
|
Gold
|
0.1 oz/ton
|
800 koz
|
Indicated
|
8,040 k tons
|
Lead
|
3 %
|
239,250 tons
|
Indicated
|
8,040 k tons
|
Zinc
|
8 %
|
643,950 tons
|
Inferred
|
1,930 k tons
|
Silver
|
13.4 oz/ton
|
25,891 koz
|
Inferred
|
1,930 k tons
|
Gold
|
0.08 oz/ton
|
154 koz
|
Inferred
|
1,930 k tons
|
Lead
|
2.9 %
|
55,890 tons
|
Inferred
|
1,930 k tons
|
Zinc
|
6.9 %
|
133,260 tons
|
Corporate Filings & Presentations:
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