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Aksug

Siberia, Russia

Main commodities: Cu Mo
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The Aksug porphyry Cu-Mo deposits are located within the Altai Sayan region of central Siberia in eastern Russia. 400 km SSE of Krasnoyarsk (#Location: 53° 25' 47"N, 96° 34' 47"E).

The deposit occurs within the Khamsarin terrane of Cambrian volcanic arc rocks on the northern periphery of the Todzhin metamorphic subterrane, all of which are cut by Late Cambrian granitoids. The closest unit with late Neoproterozoic (Vendian) to Early Cambrian ophiolites, the Kurtushibin ophiolites, which can be interpreted as a trace of the coeval subduction zone, is ~130 km to the west (Yakubchuk et al., 2012).

The deposit is localised within the Kandat Fault Zone, which cuts the granitoids of the composite Aksug Pluton. This pluton consists of at least two different intrusive suites, including Early (Silurian?) diorite-monzonite, granodiorite and granodiorite porphyries, emplaced into a 5 x 8 km gabbrodiorite to diorite intrusive massif. These units are intruded by dykes of leucocratic granite and granosyenite. The complex is also intruded by Late Devonian equigranular and porphyritic tonalite and trondhiemite.

At the deposit scale, the deposit is associated with a small cupola-shaped plagiogranite-porphyry stock, with steep-dipping (60 to 80°) contacts. The mineralisation follows the outer contact of the intrusion, which has a poorly mineralised core.

40Ar/39Ar dating of phases of the pluton has yielded an age of 497 to 462 Ma. These rocks of the pluton are intruded by stocks and dykes of ore-bearing porphyry which consist of quartz-diorite and granodiorite dated in the range 404 to 401 Ma, and 364 to 354 to 331 to 324 Ma ages, for the stocks and dykes of ore-bearing porphyry (Sotnikov et al., 2003). These dates are accompanied by Cambrian 40Ar/39Ar ages (532±3, 523±5 Ma; amphibole) for the oldest rocks at Aksug (Sotnikov et al., 2003). However, Berzina et al. (2003) reported Re-Os ages of 511±2, 516±2, and 518±2 Ma for molybdenite. Subsequently, Berzina and Berzina (2008) published 40Ar/39Ar results of 497 to 462 Ma for the plutonic phases. Recently, GRK Intergeo has obtained new Re-Os ages for early (517.4±3 Ma) and late (317.3±3 Ma) molybdenite, indicating a possible Middle Cambrian principal mineralising event and a separate Devonian event.

The stock was subjected to pervasive hydrothermally alteration, with a barren quartz stockwork in its core, and an outer well-developed pyrite halo of quartz-sericite-carbonate-pyrite, with rich copper mineralisation at depth.

Stockwork mineralisation is confined to quartz-sericite altered zones within the porphyry stocks. The mineralisation consists of two phases. The low-grade (0.1 to 0.2% Cu; 0.003% Mo) molybdenite-pyrite-chalcopyrite mineralisation is associated with the first-generation granodiorite porphyries. Subsequent emplacement of a second generation of granodiorite porphyries upgraded the initial disseminated mineralisation to produce a superimposed chalcopyrite-bornite-molybdenite assemblage (0.3 to 1.0% Cu; 0.01 to 0.02% Mo). The average Cu and Mo grades is 0.67% and 0.015% respectively. However, Yakubchuk et al. (2012) suggesty the two phases comprise an initial chalcopyrite-bornite-molybdenite assemblage and superimposed molybdenite.

The general sequence of mineral assemblages at the Aksug deposit has been distinguished as: i). quartz-pyrite with hematite, ii). quartz-molybdenite with pyrite and chalcopyrite, iii). quartz-chalcopyrite with bornite, pyrite and molybdenite, iv). tertahedrite-tennantite, enargite, galena and sphalerite, and v). quartz-calcite. At lower levels, the rocks are rich in anhydrite, and, to a lesser extent also barite and celestine.

The richest mineralisation at Aksug is in the Northern orebody, which to the west, is concealed beneath the Dashtygoi graben. Drilling in the graben has intercepted a continuation of the Northern orebody at depth of 800 to 1000 m, indicating additional potential. Geochemical and geophysical (gravity and magnetic) data indicate the potential extension of the Aksug structure to the west, beneath and along the Devonian graben, for >7 km (Yakubchuk et al., 2012).

The deposit is said to contain 4.2 Mt of Cu, 115 000 t Mo, 126 t Au and 795 t Ag in a resource of
    ~800 Mt @ 0.52% Cu, 0.014% Mo, 0.16 g/t Au, 1 g/t Ag.
Yakubchuk et al. (2012) quote resources of:
    928 Mt @ 0.52% Cu, 0.1 g/t Au

The most recent source geological information used to prepare this summary was dated: 2012.     Record last updated: 5/5/2015
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


Aksug

  References & Additional Information
 References to this deposit in the PGC Literature Collection:
Berzina, A.N., Sotnikov, V.I., Economou-Eliopoulos, M. and Eliopoulos, D.G.,  2005 - Distribution of rhenium in molybdenite from porphyry Cu-Mo and Mo-Cu deposits of Russia (Siberia) and Mongolia : in    Ore Geology Reviews   v.26 pp. 91-113.
Pollard, P.J., Pelenkova, E. and Mathur, R.,  2017 - Paragenesis and Re-Os Molybdenite Age of the Cambrian Ak-Sug Porphyry Cu-Au-Mo Deposit, Tyva Republic, Russian Federation: in    Econ. Geol.   v.112, pp. 1021-1028.
Seltmann, R., Soloviev, R., Shatov, V., Pirajno, F., Naumov, E. and Cherkasov, S.,  2010 - Metallogeny of Siberia: tectonic, geologic and metallogenic settings of selected significant deposits: in    Australian J. of Earth Sciences   v.57, pp. 655-706.
Sotnikov V I, Berzina A N, Economou-Eliopoulos M and Eliopoulos D G  2001 - Palladium, platinum and gold distribution in porphyry Cu±Mo deposits of Russia and Mongolia : in    Ore Geology Reviews   v18 pp 95-111
Yakubchuk, A., Degtyarev, K., Maslennikov, V., Wurst, A., Stekhin, A. and Lobanov, K.,  2012 - Tectonomagmatic Settings, Architecture, and Metallogeny of the Central Asian Copper Province: in Hedenquist J W, Harris M and Camus F, 2012 Geology and Genesis of Major Copper Deposits and Districts of the World - A tribute to Richard H Sillitoe, Society of Economic Geologists   Special Publication 16, pp. 403-432
Zvezdov V S, Migachev I F and Girfanov M M  1993 - Porphyry copper deposits of the CIS and the models of their formation: in    Ore Geology Reviews   v7 pp 511-549


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