Benqala, Benkala


Main commodities: Cu Ag Au
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Benqala North and South represent a small to medium sized porphyry Cu-Au system in northern Kazakhstan, approximately 450 km north of the Aral Sea, and 300 km southeast of Magnitogorsk in the Russian Urals (#Location: 51° 12' 22"N, 61° 46' 13"E).

They were emplaced within the Carboniferous Valerianov-Beltau-Kurama magmatic arc and are believed to comprise around 30 tonnes of contained gold at an average grade of 0.3 g/t, which would equate with approximately 100 Mt of ore. The hypogene Cu grade has been quoted at 0.42% Cu, with 0.55% Cu in the oxide zone.

Mineralisation is associated with Lower to Middle Carboniferous intrusions and dykes of the Sokolov-Sarbai diorite-granite complex which intrude a middle to upper Visean (Lower Carboniferous) volcano-sedimentary sequence. In the western part of the district, the latter is predominantly volcanic, comprising dacites, andesites, andesitic-basalt and basalt porphyrite, while to the east it is largely tuffs and sediments, including tuffites, tuffaceous sandstones, tuffaceous siltstones, and tuffaceous argillites, with thin interbeds of effusives and other sedimentary rocks. The mineralised intrusive comprises an early porphyritic quartz diorite and later associated granodiorite and plagiogranite porphyries. Pre-ore dykes of granite porphyry and post ore micro-dolerite, dolerite and lamprophyre are widespread.

Mineralisation is present as a stockwork which is restricted to the northwestern margin of the host porphyry. The main ore zone has dimensions of more than 1200 x 700 m and extends to a depth of 700 m. It has been subjected to oxidation to 110 m below surface, which is thickest over the immediate ore deposit and its altered hosts. Alteration comprises an early alkaline phase characterised by albite, K feldspar, biotite, silica and tourmaline, accompanied by a propylitic halo of chlorite, epidote and prehnite. This was overprinted by an acid quartz-sericite phase and the development of chlorite and carbonate alteration. The principal metallic minerals are pyrite, chalcopyrite and magnetite, with minor molybdenite, bornite, chalcocite, digenite and rutile (Seltmann et al., 2004).

The most recent source geological information used to prepare this summary was dated: 2004.    
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.


  References & Additional Information
   Selected References:
Plotinskaya, O.Yu., Grabezhev, A.I., Tessalina, S., Seltmann, R., Groznova, E.O. and Abramov, S.S.,  2017 - Porphyry deposits of the Urals: Geological framework and metallogeny: in    Ore Geology Reviews   v.85, pp. 153-173.

   References in PGC Publishing Books: Want any of our books ? Pricelist
Seltmann R and Porter T M, 2005 - The Porphyry Cu-Au/Mo Deposits of Central Eurasia: 1. Tectonic, Geologic & Metallogenic Setting and Significant Deposits,   in  Porter T M, (Ed),  Super Porphyry Copper and Gold Deposits: A Global Perspective,  v2  pp 467-512
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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