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MNV

Overview
Geology
Mineral Resources & Ore Reserves
Mining
Mineral Processing

Overview

Mnogovershinnoe is located in the Nikolaevsk area of the Khabarovsk Territory in the far-east of the Russian Federation. The mine is located some 650 km north of the city of Khabarovsk and is accessed from Nikolaevsk-na-Amure, the principal regional centre, via a 132 km long gravel road.

The Mnogovershinnoe deposit was discovered in 1959 and detailed exploration commenced in 1963. Preliminary construction started in 1979, the mineral processing facilities were constructed between 1990 and 1993 and preliminary production started in 1991. Between 1991 and the present day the mine has produced over 2 million oz of gold.

MNV location map Click to enlarge
Thumbnail of Mnogovershinnoye (MNV) location map

The Group owns 100% of the MNV joint-stock company, which has a licence for the extraction of gold ore valid until December 2018. Operations at MNV consist of both underground and open-pit mining of several high grade gold deposits. In addition, MNV has its own gold processing plant. MNV was initially brought into production by its previous owners in 1991 and operated until 1997, when the mine was closed due to poor technical and financial performance and a lack of funds for reconstruction and development. Following a change of ownership and the introduction of a new management team, gold mining and gold extraction recommenced in 1999 under the direction of the new management team. Subsequent capital investment in mining and metallurgical equipment has meant that the technical performance of the mine has significantly improved over recent years.

Geology

The Mnogovershinnoe (MNV) gold deposit is located at the junction of the Amgun synclinorium and the East Sikhote-Alin volcanic belt. The area is characterised by numerous subvertical faults which control location and orientation of the volcanics, intrusives and gold and silver mineralisation. The mineralisation occurs over an area of some 120 km2.

The Mesozoic basement rocks in the MNV area encompass sandstones, siltstones and shales which are overlain unconformably by late-Mesozoic to Paleogene andesitic volcanics. Both the basement sediments and the overlying volcanics have been intruded by numerous dykes of granodiorite, granite and porphyries.

Mineralisation is controlled by major north-easterly trending faults. Post-mineral block faulting of north-west orientation caused segmentation of the mineralization zones along strike.

Mineralization consists of silicified and veined fault breccias and displays banded quartz-chalcedony-carbonate textures typical of low-sulfidation style epithermal deposits. The total sulphide content is relatively low (<2%) and consists primarily of pyrite-marcasite. Quartz constitutes more than 95% of the ore bodies. Gold is distributed irregularly in the form of fine disseminated impregnations, small individual pockets and thin veinlets.

MNV geology map Click to enlarge
Thumbnail of Mnogovershinnoye (MNV) geology map

The ore bodies at Mnogovershinnoe are located within the Main Zone and the Intermediate Zone. The Main Zone is some 5.8 km long and contains the Central, Upper and Reindeer ore bodies. The Intermediate Zone is some 6.2 km long and is located 1.5 km north-west of the Main Zone and contains the Intermediate I and II ore bodies together with the South, Flank, North, Deep, Quiet and Pebble ore bodies. The overall width of the two zones is some 2.5 km. All ore bodies strike north-easterly and dip steeply to the north-west. Generally, both thickness of ore bodies and distribution of gold grade are highly irregular.

The Main Zone is confined to a steeply dipping fault and marks a central quartz vein system surrounded by a zone of veinlet-impregnated silicification. The total thickness of the zone varies from 10 m to 60 m. The structure of the Main Zone is complicated by numerous post-mineralisation faults and intrusions.

The Intermediate Zone is likewise confined to a steeply dipping fault and consists of a thick quartz vein surrounded by a halo of quartz veinlets. The total thickness of the zone varies between 20 m and 80 m. The Intermediate Zone is subdivided into blocks by a number of north-west trending faults with vertical displacement.

The majority (92-96%) of the gold and silver (80-90%) occurs in a free form amenable to standard cyanidation leaching. Minor amounts also occur as fine inclusions in quartz, other rock-forming minerals and sulphides. Visible gold is uncommon and cyanide leaching test work confirms that the gold is non-refractory, with extraction levels of over 90% being achievable at standard grind parameters.

Mineral Resources & Ore Reserves

Mnogovershinnoe Mineral Resource Statement as at 31 December, 2012
Reported in accordance with JORC
Ore, tonnes
Gold
(g/t)
Contained gold,
ounces
Measured
3,136,061
4.2
421,953
Indicated
872,256
4.1
116,063
Measured + Indicated
4,008,317
4.2
538,016
Inferred
3,294,000
4.4
465,575
Total
7,302,317
4.3
1,003,591


Mining

Mining at Mnogovershinnoe is done by both open pit and underground methods. In 2011, open pit and underground mining provided 744.6 and 527.7 thousand tonnes of ore, respectively.
Open pit mining at MNV Click to enlarge
Thumbnail of Underground mining at MNV

Open Pit
Mining is standard open pit benching. Waste benches of 10 m and ore benches of 5 m are drilled using both Atlas Copco and Russian-made drill rigs with hole diameters of 125 mm to 250 mm. Holes are charged with Anfo(Ammonium Nitrate Fuel Oil) and the blasting ratio is 0.25 kg/t of rock (ore and waste). The overall pit slopes are between 45º and 55º. The mountainous topography enables the pits to be designed to minimise water pumping and maximise the advantages of downhill haul gradients.

Primary loading is done using a combination of diesel and electric shovels. Belaz trucks of 55 t and CAT trucks of 40 t capacity are used for ore and waste transport.

Underground

The mining method currently in use is long hole sub-level caving with an interval of 14 m between sub-levels. 100 mm diameter long holes are drilled up from each sub-level using a Russian drill rig. Development is undertaken using modern mobile jumbo drill rigs and LHDs.

Ore is loaded from the draw points using modern diesel-powered 3.5m3 LHDs. The ore is either tipped into a central ore pass system where it gravitates into a series of loading chutes on the No11 level or loaded onto u/g trucks for delivery to surface via declines. At No 11 level both ore and waste is loaded from the chutes into 2.6 m3 wagons which are hauled to the tip at the mouth of the adit by a locomotive powered by electricity from an overhead power line. Ore and waste is loaded at the surface tip by a conventional front end loader into 40 t off-road trucks and transported 3.6 km to the mill or the waste dump.

Mineral Processing

Pre-blended ore is delivered to the plant feed hopper by trucks, which either direct tip or stockpile for subsequent feeding via the front-end loader. Ore is withdrawn from the base of the bin by an apron feeder, which is then fed through a jaw crusher. Crushed ore is conveyed to a series of 14 feed hoppers.
The MNV processing plant and administration building Click to enlarge
Thumbnail of The MNV processing plant and administration building

The milling circuit comprises two 7.0 m x 2.3 m SAG mills each fitted with 1,600 kw motors and three 3.6 m x 4.0 m ball mills each fitted with 1,000 kw motors. The normal running format is to operate two SAG mill with three ball mills.

SAG discharge pulp passes into a spiral classifier. The spiral overflow is pumped through a series of hydro cyclones generating a final product of 85% minus 74 microns. Some of the flow is split to several centrifugal gravity concentrator units which pull a percentage of gravity gold which is then processed by an in-line leach reactor. The cyclone overflow is pumped to the cyanide leach circuit. Following pH adjustment, sodium cyanide is added at a rate of between 0.8 to 1.0 kg per tonne of ore and the pulp is then leached for approximately 10 hours. The pulp then passes through the resin absorption circuit, where leaching of gold from the ore and absorption onto the resin particles continues for a further 10 to 12 hours.
Inside the MNV milling complex Click to enlarge
Thumbnail of Inside the MNV milling complex

Loaded resin is periodically removed from the leaching circuit and treated through the desorption and electro winning system to generate plated cathode gold. This gold is then smelted to produce bullion bars, which are shipped off site for final refining.

Leached pulp containing approximately 300 to 400 ppm residual cyanide is neutralised using the calcium hypochlorite technique, prior to being deposited in a tailings facility approximately 4 km from the plant. All decanted water is recycled from the dam and returned to the plant; any additional make up water requirements are drawn from a nearby stream.