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Zun-Holba Mine
The Zun-Holba mine is a producing underground cut and fill mining operation with a conventional carbon-in-pulp (CIP) processing plant. It is located in the Republic of Buryatia, Russia, approximately 315 kilometres by road from the Trans-Siberian Railroad, at the southwest end of Lake Baikal.
Geological Setting and Mineralization
The Zun-Holba deposit occurs within a narrow northwest trending anticline situated between two Archean intrusives (see geological map below). The anticline is composed of a sequence of strongly folded and metamorphosed Proterozoic volcanics and sediments (limestones, sandstones, schists and tuffs), and strikes northwest over 7 kilometres within the property, plunging 40-45 degrees to the southeast.
Click on image to enlarge
Gold mineralization is structurally controlled by 3 subparallel shear zones running axially along the anticline. Gold mineralization occurs within 13 subvertical, en echelon gold-bearing mineralized zones containing quartz-sulphide veins with strike lengths of 50 to 100 metres. The mineralized zones range from 0.3 to 8 metres in thickness, averaging approximately 2 metres. The combined ore-bearing zones measure about 3 kilometres along strike and have been traced to a minimum depth of 1 kilometre.
Gold mineralization is largely associated with quartz-sulphide veins, with some occurring in altered host rocks as well. Pyrite amounts to 7-8% of the mineralized rock by volume. Gold within the ore is disseminated and very fine grained (less than 0.07 mm).
History
The Zun-Holba deposit was initially discovered in 1955. Mine development and initial limited production started in 1986. Buryatzoloto acquired the license for Zun-Holba in 1991 and assumed control of day-to-day operations from the sub-contractor of the project in 1993. In 1995, Buryatzoloto became an open joint stock company and, shortly thereafter, 30% of the company's shares were acquired by High River via an open cash auction. High River increased its ownership in Buryatzoloto to 85% by 2005.
Mining
Mining methods currently used at Zun-Holba are cut and fill stoping (58% of production) timbered (square set) stoping (33% of production), and shrinkage stoping (9% of production). The Zun-Holba mine operates with a series of adits and internal shafts. Mining is currently focussing on the lower sections of the ore body.
Click on image to enlarge
| Operational Data |
2008 |
2007 |
|
|
|
| Tonnes mined |
286,000 |
266,000 |
| Tonnes milled |
272,000 |
260,000 |
| Head grade (g/t) |
8.3 |
8.9 |
| Recovery (%) |
95.3 |
93.9 |
| Gold production (oz) (100%) |
69,551 |
69,474 |
| Cash Operating Cost (US$/oz) |
649* |
422* |
*plus 6% government royalty
Processing
Gold recovery from the processing plant is approximately 95%. Ore is processed using the following flowsheet (see diagrams below):
- Two crushing stages
- Two grinding stages using ball mills
- Gravity separation produces concentrates for both the gravity and flotation circuits
- Gravity circuit to recover free gold (approximately 33% of total gold production)
- Flotation to recover finer gold particles into a flotation concentrate
- Cyanidation process and absorption leaching of the flotation concentrate
- Smelting to produce gold/silver dore bars
The Zun-Holba processing plant also processes flotation concentrate produced at Irokinda.
Mill Processing Flowsheet
CIP Processing Flowsheet
Exploration Potential
Known mineralization at the Zun-Holba mine is open along strike and at depth (see blue shading in Longitudinal Section under section titled "Mining" above). The mineralization does not appear to be constrained by any major geological features, although some cross-cutting faults appear to have offset the mineralization. Currently, underground drilling is testing this potential.
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