Berezovskoe Belousovskoe Ore Field - Berezovskoe, Berezovsky, Belousovskoe, Novo Berezovskoe
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Berezovskoe is one of a group of deposits that includes Belousovskoe / Belousovsky and Novo-Berezovskoe, which together make up the Berezovskoe-Belousovskoe ore field. The ore field is located in the regional Irtysh Kink Zone, in the Rudny Altay district of Kazakhstan. It is 70 km WSW of Ridder, 170 km ESE of Semey [Semipalatinsk] and 18 km NNW of Oskemen (#Location:50° 7' 22"N, 82° 30' 25"E).
The Berezovskoe-Belousovskoe ore field is hosted within volcanogenic and sedimentary rocks that were deposited between the late Silurian and the lower Carboniferous. The structure in the deposit area is a combination of plate and lens-like blocks of moderately to slightly altered rock, enveloped by linear bodies of injective-tectonic mélange (Kozlov, et al., 1987).
The host sequence in the orebody area comprises:
Late Silurian to lower Devonian Kremenyushinskii Formation, which is >500 m thick, and in the orebody area is a narrow tectonic wedge of diverse altered tuffs and volcano-terriginous rocks (meta-conglomerates, meta-psammites and meta-pelites containing volcanic litho-clasts);
Devonian Shipulinskii Formation, divided into the,
Lower Series, which has in turn a lower, "Bed a", which is 150 m thick, and is composed of pyrite-bearing coaly-calcareous-clayey siltstone with horizons and lenses of limestone; pyrite-siliceous-clayey rocks; dolomite and siliceous dolomite bands, lenses and veins; and "Bed b", which is up to 140 m thick and consists of pyrrhotite bearing siltstones and silty shales with rare thin lenses and bands of siliceous meta-argillaceous rocks, and individual lenses of limestone and dolomite.
Upper Series, which is 430 m thick, commences with a bedded, thick (to 30 to 40 m) unit composed of pyrite-siliceous-meta argillaceous rocks, silicates, dolomites, chloritic rocks, sulphides and copper-pyrite ore. Various hydrothermal-sedimentary litho-facies are distributed as lenses and pinchout layers up to 400 to 500 m long, 100 m wide and 5 to 10 m thick. This sulphidic unit is replaced (laterally?) by uniform coaly-clayey siltstones with poor to 1% phenocrysts of pyrite and pyrrhotite. Extrusive bodies of quartz-biotite-albitophyres and associated coarse detrital horizons, along with beds of psammites and grits appear in the upper part of the Upper Series.
The Shipulinskii Formation is notable for its saturation by sulphides, mainly pyrite and pyrrhotite.
Intrusive rocks found within the ore-field include sub-extrusive albitophyres of Eifelian age; sub-volcanic and hypo-volcanic(?) intrusives of diorite, plagiogranite, andesite porphyry and felsite porphyry of late Devonian age; and a lower Carboniferous gabbro-pyroxenitic complex (Kozlov, et al., 1987).
More than 10 ore lenses have been identified, occurring at three different stratigraphic levels over a 600 m vertical extent from the surface (IMC Group Consulting Ltd, 2011, in a Competent Persons Report to Kazakhmys Plc).
The ore deposits are located within the Berezovskii tectonic block, which is 600 m wide and 10 km long, and is separated on all sides from neighbouring blocks by narrow, linear mélange zones. The mélange zones are around 150 m thick and composed of highly deformed metamorphic greenschist after the upper Silurian to lower Devonian volcano-sedimentary rocks of the Kremenyushinskii Formation. The Berezovskii tectonic block dips at 75 to 80° to the north-east, while the component beds dip at 50 to 75°, also to the north-east (Kozlov, et al., 1987).
The ores are composed of pyrite and marcasite with chalcopyrite, sphalerite, galena, valleriite, magnetite, sulphosalts if silver, stromeyerite, bournonite and arsenopyrite, and are hosted in Eifelian rocks of the middle Devonian. The pyrite has a high degree of crystallinity and occurs as massive and banded sulphides. Abundant sulphide and quartz-sulphide veining is also recorded. Only relict early colloform framboidal pyrite remains. The gangue includes calcite, quartz, muscovite-sericite, ferro-magnesite, chlorite and actinolite (Kozlov, et al., 1987).
Zinc grades are relatively evenly distributed, but copper shows a pronounced decrease from the base of the ore lenses to the top (IMC Group Consulting Ltd, 2011, in a Competent Persons Report to Kazakhmys Plc)
Strong hydrothermal alteration is obvious in the sequence, including the transformation of siliceous-dolomite rock to form lenses of talc, hydromagnesite-talc rocks, talc-chlorite and chlorite schists up to 2 km long, with a thickness of up to 10 m. Kozlov, et al., (1987), conclude that low grade pyritic mineralisation was first emplaced during the middle Devonian (Eifelian), but has been remobilised and hydrothermally enriched in the lower Carboniferous under higher temperatures and pressures accompanying the intense deformation adjacent to the Berezovskii tectonic block. They also argue that the later base metal sulphides were nucleated on the earlier, mainly pyritic mineralisation.
Mining commenced at Belousovsky in 1939.
Mineral resources remaining as at 1 January, 2011 were (IMC Group Consulting Ltd, 2011. Competent Persons Report to Kazakhmys Plc):
Measured resource - 4.326 Mt @ 0.75% Cu, 4.18% Zn, 0.66 g/t Au, 57.95 g/t Ag, 1.05% Pb;
Indicated resource - 8.027 Mt @ 0.41% Cu, 3.58% Zn, 0.35 g/t Au, 46.79 g/t Ag, 0.80% Pb;
TOTAL resource - 12.353 Mt @ 0.53% Cu, 3.79% Zn, 0.45 g/t Au, 50.70 g/t Ag, 0.89% Pb;
Ore reserves (same date and source - included in resource)
TOTAL proved + probable reserve - 0.264 Mt @ 1.85% Cu, 1.12% Zn, 0.38 g/t Au, 27.50 g/t Ag, 0.18% Pb.
The most recent source geological information used to prepare this summary was dated: 1997.
Record last updated: 15/5/2013
This description is a summary from published sources, the chief of which are listed below.
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