The Vasilkovskoye gold deposit is located 17 km north of Kokshetau in the Akmola Oblast in northern Kazakhstan. First discovered in 1963, the deposit was exploited by a pilot open pit mine from 1980-1986 and again from 1995-2007. Oxide ores were processed using heap leach technology and production is believed to be approximately 14 Mt up to 2011.
Currently operated by Kazzinc, a subsidiary of GlencoreXstrata Plc the mine has a production capacity of 8 Mtpa and construction of an underground extension to the existing open pit is expected to commence in 2013.
The Vasilkovskoye deposit is located in the NW-trending Shatskaya metallogenic zone within the Altai-Sayan Orogenic Belt. The deposit is located within the contact aureole of the Altybaysky granite intrusion (regionally the Ordovician Zerendinsky Complex) which has intruded a Precambrian metamorphic basal complex. A Mesozoic weathering profile is preserved and overlain by Cenozoic sand and clay sediments.
In the north of the deposit area a weakly mineralised diorite/gabbrodiorite suite represents the transition from the metamorphosed country rocks to the Altybaysky granite intrusion. A granite/granodiorite suite occupies the majority of the sourthern part of the deposit and hosts the majority of the mineralisation. In the south of the deposit quartz-diorites, diorites and gabbrodiorites have been intersected at depths of 400-500m. These intrusions may be related to the Stepnyaksky Complex, paragenetically related to the main gold deposits of northern Kazakhstan.
The Vasilkovskoye intrusion-relation gold deposit is cross-cut by numerous structures. The majority of these structures mimic the trend of the regional NW-trending Dongulagashsky fault and NE-trending Vasilkovskoye fault. Mineralisation is spatially associated with a stockwork of hydrothermal quartz and quartz-arsenopyrite veins and occurs as a flattened zone controlled by the intersection of the above faults and the contact aureole of the Alyybaysky granite, pinching out at depth.
Sulphides are dominated by arsenopyrite occurring in sulphide veins, with quartz veins, as disseminations, with native gold and with minor pyrite and trace amounts of chalcopyrite, bismuth sulphides and bismuth tellurides. Other sulphides present include sphalerite, galena, molybdenite, stibnite and tennantite. All sulphides occur throughout the deposit but pyrite and chalcopyrite are more commonly associated with the mafics. Uranium mineralisation also occurs in the deposit with grades up to 100 ppm. Uranium mineralisation appears to be later and grades outside of the gold deposit envelope exceed 1%.
Gold grade is associated with thin (<3 cm) microcrystalline quartz veins and veinlets oriented at a high angle to the main structures. Typically these veins occur 1-5 per metre but increase in concentrations of >10 per metre.
Alteration is concentrated in steeply dipping lenses and occurs as: chlorite; chlorite-albite; albite; carbonate; quartz-sericite; quartz-k-feldspar; k-feldspar; argillite. Ore phase alteration accompanied sulphide-quartz stockwork development and is dominated by quartz-sericite (phyllic) alteration and filling of vesicles. Argillic alteration post-dates mineralisation.
JORC compliant mineral resources at 1 Jan, 2011 (Wardell Armstrong 2011, for Kazzinc Glencore) were:
0.4 g/t Au cut-off
Measured + indicated resource - 186.80 Mt @ 1.72 g/t Au for 320 t of gold;
Inferred resource - 99.08 Mt @ 1.77 g/t Au for 175 t of gold;
0.9 g/t Au cut-off
Measured + indicated resource - 128.49 Mt @ 2.22 g/t Au for 286 t of gold;
Inferred resource - 68.63 Mt @ 2.27 g/t Au for 156 t of gold;
1.5 g/t Au cut-off
Measured + indicated resource - 78.49 Mt @ 2.90 g/t Au for 227 t of gold;
Inferred resource - 39.74 Mt @ 3.07 g/t Au for 122 t of gold;
JORC compliant ore reserve at 1 Jan, 2011 (Wardell Armstrong 2011, for Kazzinc Glencore), using a 0.48 g/t Au cut-off were:
Proved + reserve - 33.3 Mt @ 1.95 g/t Au for 65 t of gold;
Probable + reserve - 90.7 Mt @ 1.94 g/t Au for 176 t of gold;
TOTAL reserve - 123.97 Mt @ 1.94 g/t Au for 240 t of gold.
(Source: Porter GeoConsultancy, www.portergeo.com.au , 2013)
(Source: <http://www.kazzinc.com/#en/Operations/Organization of operations/Kokshetau/Altyntau Kokshetau/> accessed 20/08/2013)
(Source: Newell et al., 2011. Competent Person’s Report for the Assets held by Kazzinc Limited in Kazakhstan and Russia; prepared by Wardell Armstrong International, Truro, UK.)