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The Koktenkol Mo-W deposit is located ~160 km SSW of Karagandy and ~300 km NW of Balkash (Balqash) in Kazakhstan (#Location: 48° 36' 12"N, 72° 13' 31"E).
Koktenkol lies within the middle to late Palaeozoic Kazakh-Mongol magmatic arc of Central Asia, that also hosts the Nurkazgan porphyry Cu-Au deposit ~180 km to the north, and other major porphyry Cu-Au deposits to the SE, closer to Balqash.
The Koktenkol deposit occurs as a stockwork of quartz, quartz-feldspar and feldspar veinlets which carry molybdenite, wolframite, pyrite, chalcopyrite, bismuthinite, magnetite, hubnerite, rutile, muscovite, quartz, fluorite, feldspars, calcite, garnet and other minor minerals. The stockwork and its associated mineralisation is developed within a middle to upper Devonian sequence of volcanogenic and sedimentary rocks, above the apex of an oval shaped lower Permian or Upper Carboniferous, leucocratic granitic complex (Smirnov, 1977).
The granite apex outcrops over an area of 0.15 km2, but widens considerably with depth to form a concealed 15 x 18 km batholith. The Devonian sequence comprises andesite and dacite porphyries, with tuffs of rhyolite porphyry, interstratified with sandstones, siltstones and tuffaceous sandstones. These are overlain by carbonaceous chert, shales, marls and limestones of late Devonian age. Around the granites the Devonian alumino-silicates have been hornfelsed, intensely biotitised and feldspathised, and the carbonates have been skarn altered (Smirnov, 1977).
Alteration within the granite includes K-feldspar and more prominent albite development, followed by quartz veining, first containing molybdenite, then by wolframite, pyrite, bismuthinite, molybdenite, muscovite and fluorite. Later veining introduced further stages of wolframite, pyrite, chalcopyrite, magnetite, fluorite and muscovite and other minerals (Smirnov, 1977).
The southern sector of the deposit, which contains the bulk of the resource, is developed within Devonian volcanics which have been intensely altered by contact metamorphism. In the northern sector the stockwork is mainly included within metamorphosed Devonian rhyolite tuffs, tuffaceous sandstones, sandstones and skarn altered limestone, near the apex of the batholith. A minor proportion of the ore is contained within the granite itself. The main deposit covers an area of ~900 x 1200 m and extends from the surface down to an average depth of 550 m. Ore is developed over a maximum vertical interval of 800 to 900 m, 100 to 200 m of which is in the granite (Smirnov, 1977; Dala Mining, 2011).
The Koktenkol stockwork lies in a NNW striking tectonic zone which passes across the deposit. The veins of the stockwork vary from 1 to 2 mm, up to 100 to 150 mm, averaging 5 to 20 mm. The densest network of veining is above the upper-central axial portion of the granite, especially a dome like rise in its surface. Away from domal culminations, the network of veins diminishes and the mineralisation dies out. The maximum amounts of Mo are concentrated at the granite exo-contact above its apical portions, with only a small amount in the granite itself. The largest amounts of WO3, Bi and Sn correspond to the maximum Mo, while Cu occurs on the flanks of the deposit. The highest Pb values are lower in the system in the core portions of the Mo zone, decreasing towards the peripheries (Smirnov, 1977).
Published ore reserves and mineral resources in 2013 (Dala Mining LLP, website, 2013) at a cut-off grade of 0.04% Mo, were:
Proved reserve - 429.1 Mt @ 0.077% Mo, 0.152 g/t Re, 0.005% Bi, 0.038% Cu;
Inferred resource - 62.9 Mt @ 0.078% Mo, 0.152 g/t Re, 0.005% Bi, 0.030% Cu (additional to reserve);
The most recent source geological information used to prepare this summary was dated: 2011.
Record last updated: 11/9/2013
This description is a summary from published sources, the chief of which are listed below.
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