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Blagodatnoe, Blagodat |
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Siberia, Russia |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Blagodatnoe or Blagodat gold deposit is located on the Yenisey ridge, some 25 km north of the Olympiada deposit on the southwestern margin of the Siberian Shield in Russia.
The Yenisey ridge is a complex Precambrian fold belt on the margin of the Siberian craton adjacent to the Western Siberian terrane. Two segments of the fold belt, which are characterised by NW-trending structures, are separated by the ENE-trending Angara Fault, a strike-slip structure. North of the Angara Fault, the Yenisey ridge is predominantly composed of Neoproterozoic rocks, comprising the East Angara, Central Angara and Isakov terranes (after Vernikovsky et al., 2003). These three terranes were subjected to widespread thrusting and regional metamorphism during the late Mesoproterozoic (Late Riphean) Baikal tectonic stage.
The bulk of the known gold deposits of the Yenisey ridge are located in the Central Angara terrane, the internal structure of which is represented by a combination of narrow anticlinorriums and wider synclinoriums with local domes in the central part exposing the Palaeoproterozoic rocks. The Central Angara terrane comprises flysch-like and carbonate sediments that were metamorphosed from greenschist to amphibolite facies, reflected by increasing temperatures of regional metamorphism, from greenschist on the wings of anticlinoriums to amphibolite grade in their cores. In some cases, the spatial transition from the regionally metamorphosed low-pressure (andalusite-sillimanite type) rocks to higher-pressure rocks is marked by a kyanite isograde near largest thrust faults (Likhanov, Reverdatto, 2002). All these rocks were intruded by the syntectonic (Baikal), anatectic, 760 Ma Tatar-Ayakhta calc-alkaline granites (Vernikovskaya et al., 2003) and by smaller bodies of 720-750 Ma late- or post-tectonic Glushikha leucogranites (Vernikovsky et al., 2003; Vernikovskaya et al., 2002). In general, these, granitoids are focussed along the NW trending axes of anticlinoriums. The latest magmatic activity in the region accompanied continental rifting with the development of small 640-680 Ma (Early Vendian) alkaline basic and ultrabasic intrusions (Vrublevsky et al., 2003).
The gold-bearing sulphide mineralisation of the Blagodat deposit was formed in the upper section of the Mid-Mesoproterozoic Corda Formation rocks that are represented by staurolite- and garnet-bearing micaceous schists, metamorphosed to epidot-ampholite grade, defining three lithological units, namely: (i) staurolite-bearing; (ii) micaceous and (iii) quartz-rich schists. The staurolite-bearing schists are more widespread in the lower part of the vertical section, whereas micaceous and quartz-rich schists are located higher in the succession. In addition, quartz-rich and arkosic meta-sandstones and muscovite-bearing meta-siltstones in the middle section of the Corda Formation and calcareous rocks of the Palaeoproterozoic Ryazanov Formation, are located on the eastern flank of the Blagodat deposit.
Three main stages of deformation are evident: (i) an early stage defined by thrusting and folding of primary sedimentary layers with a local progressive metamorphism, forming NW-trending thrust-fold systems; (ii) a NW-trending, sub-parallel shear zone, developed along a synclinal hinge in the central part of thrust sheet under conditions of retrograde metamorphism, occurring as a normal fault with sinistral strike-slip displacement that controlled the gold-bearing sulphide mineralisation, represented by diamond-shaped ore bodies that suggest duplex or en echelon "pull-apart" structures; and (iii) late stage deformation that continued in a similar dynamic regime leading to a transverse dislocation of the deposit by N-trending normal faults.
Gold occurs in a wide range into ore bodies and is reflected by the accumulation of metal predominantly in local fracture zones within hinges of high order folds. Granite intrusions are rare in the mineralised area where is is mainly present as dykes of the Tatar-Ayakhta complex. The gold-bearing mineral paragenesis includes pyrrhotite, pyrite and arsenopyrite in association with quartz. Late smaller fluorite-carbonate veins additionally contain chalcopyrite, sphalerite and galena.
The Blagodatnoe operation is scheduled to produce ~12.8 t of gold per annum from 6 mtpa of ore treated. Mineral resources in 2010 were (Polyus Gold website):
Measured resources - 3.4 Mt @ 2.50 g/t Au;
Indicated resources - 132.8 Mt @ 2.40 g/t Au;
Indicated resources - 36 Mt @ 2.20 g/t Au;
for a combined 410 tonnes of contained gold
Remaining JORC compliant Ore Reserves and Mineral Resources at 31 December 2017 were (Polyus Ore Reserves and Mineral Resources Update 20 March, 2018):
Proved + Probable Ore Reserves - 216 Mt @ 1.4 g/t Au for 299 t of contained gold;
Measured Mineral Resources - 52 Mt @ 0.9 g/t Au;
Indicateded Mineral Resources - 292 Mt @ 1.5 g/t Au;
Inferred Mineral Resources - 69 Mt @ 1.3 g/t Au;
TOTAL Mineral Resources - 413 Mt @ 1.4 g/t Au for 578 t of contained gold;
This summary was paraphrased from Sazonov et al., 2009, Journal of Siberian Federal University, Engineering & Technologies v. 2, pp. 203-220
The most recent source geological information used to prepare this decription was dated: 2011.
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.
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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, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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