The Kosmurun and Akbastau volcanic hosted copper-gold deposits are 8 km apart in eastern Kazakhstan, ~35 km WNW of the town of Koryk, ~280 km NE of Balkhash and 260 km SW of Semey.
These deposits are hosted within rocks of the Ordovician Kipchak volcanic arc, parallel to and ~450 km to the SW of the Middle Devonian Rudny Altay Volcanic Arc that hosts many of the important volcanic hosted massive sulphide (VHMS) deposits of Kazakhstan.
Kosmurun comprises an upper lens shaped oxidised orebody that was mined out to a depth of 100 m in an open pit to produce 2.7 Mt of ore from 2006 to 2008. The grades in 2007 were 3.55% Cu, 2.77% Zn. The ore was trucked 225 km to a concentrator in Karagaily.
A lower orebody, the top of which is ~200 m below the surface, and ~75 m in the footwall of the upper lens, is composed of massive sulphide up to 150 m thick, with a strike length of 400 to 450 m and down dip extent of ~300 m. This lens tapers and thins on its lateral and down dip margins.
Estimated resources are (IMC Technical Report to Kazakhsmys, 2011):
Measured resource - 16.034 Mt @ 3.15% Cu, 0.76% Zn, 0.86 g/t Au, 17.5 g/t Ag
Indicated resource - 1.539 Mt @ 3.13% Cu, 0.76% Zn, 0.86 g/t Au, 17.54 g/t Ag
TOTAL resource - 17.573 Mt @ 3.15% Cu, 0.76% Zn, 0.86 g/t Au, 17.5 g/t Ag.
Akbastau, which is ~8 km to the NW of Kosmurun, was mined by open pit to a depth of 50 m in 2007-08 to produce 1.4 Mt of oxide ore, which in 2008 graded 2.5% Cu, 0.63% Zn. The deposit basically comprises a single lens, which outcrops, with a strike length of 550 m, thickness of up to 150 m and dip of 75°. At depth the sulphides thin and divide, before pinching out at ~350 m down dip. Approximately 35% of the resource is classified as mixed oxide and sulphide, with oxidation persisting to a depth of ~100 m. Only 10 to 20% of the sulphides are massive, with the bulk being disseminated.
Estimated resources are (IMC Technical Report to Kazakhsmys, 2011):
Measured resource - 8.199 Mt @ 1.7% Cu, 1.10% Zn, 0.54 g/t Au, 13.79 g/t Ag
Indicated resource - 2.852 Mt @ 1.65% Cu, 0.70% Zn, 0.53 g/t Au, 17.54 g/t Ag
TOTAL resource - 11.051 Mt @ 1.69% Cu, 1.00% Zn, 0.54 g/t Au, 13.48 g/t Ag.
(Source: Porter GeoConsultancy, www.portergeo.com, 2015)
