|
Bakyrchik |
|
|
Kazakhstan |
| Main commodities:
Au
|
|
 |
|
|
 |
Super Porphyry Cu and Au
|
IOCG Deposits - 70 papers
|
All available as eBOOKS
Remaining HARD COPIES on
sale. No hard copy book more than AUD $44.00 (incl. GST) |
|
|
The Bakyrchik gold deposit is located in north-eastern Kazakhstan, approximately 1100 km northeast of Almaty and 160 km southeast of Semipalatinsk. The deposit was discovered in the 1950's and opened for production in 1965 (#Location: 49° 43' 6"N, 81° 34' 53"E).
The deposit is one of a number of occurrences and deposits within the Kalba Gold Belt which lies within the central portion of the Kalbinsky synclinorium in the core of the north west trending Irtysh-Zaisan Zone mobile belt. It is hosted by Lower and Middle Carboniferous marine sediments of the Kalba-Narymsk structural zone.
The Carboniferous hosts comprise a sequence of predominantly sandstone and shale which, on the basis of geophysical measurements, is estimated to be 6 to 9 km thick. These sediments are believed to overlie 2 to 3 km of carbonates, which in turn are underlain by 4 to 5 km of relatively mafic extrusives and tuffs (Poltorykhin, 1974). This sequence has been complexly folded and faulted. The folds are mainly north-west trending, while the faulting trends in a similar north-west direction as well as sub-latitudinally.
These faults control the distribution of numerous small Permo-Carboniferous granitoid stocks and dykes which occur as chains along these structures (Poltorykhin, 1974). The granitoids are found as single stocks, while the numerous dykes are represented by plagiogranite porphyries, diorites, spessartites, kersantites, gabbro-diorites and gabbro-dolerites. The earliest intrusives are silicic and felsic, while the later are sub-alkalic varieties and are intermediate in composition. The more acid plagiogranites and the intermediate microdiorite, spessartites and kersantites are all pre-ore, while the gabbro-dolerites are probably Triassic and are post ore. The gabbro-diorites and plagiogranites are believed to be related to a Permo-Carboniferous intrusive phase which is equated with the formation of ore (Korobeinikov, 1990). Geophysical data indicates larger Permo-Carboniferous granitoid intrusives at a depth of 3 to 5 km (Poltorykhin, 1974).
The Kalba - Narymsk structural zone occupies a narrow 10 to 15 km wide strip lying between two prominent parallel northwest trending regional faults, the Kabinsky Fault Zone to the west and the Northeast Fracture on the east. Two main cross zones are known as the Kyzyl Shear (KZS) and the Parallel Zone (PZ). All contain gold bearing lenses within the shears with better mineralisation located in proximity to fault intersections.
The gold deposits consist both as a series of mineralised lenses or lodes closely controlled by faulting, and as zones of disseminated sulphides.
The lodes are mainly within the Kyzyl Shear which strikes east-west and dips about 35 to 40° N and forms a roughly tabular zone 11.5 kilometres in length consisting of strongly brecciated and sheared sediments. Gold mineralisation within the Kyzyl Shear is hosted by five mineralised zones numbered 1, 3-4-5, 8, 9-10 and 12 within carbonaceous ( 0.3 to 5% Corg) interbedded siltstones, sandstones, mudstones and claystones of the Kokpecty Formation. These mineralised lenses have been traced from surface to more than 1000 metres in vertical depth by diamond drilling.
The disseminated sulphide orebodies are crumpled, fractured, hydrothermally altered and sulphidised, carbonaceous sandstone-shale masses, including shungite, argillite, siltstone and sandstone. The sulphides, which account for 3 to 5% of the orebody mass, are usually finely disseminated, or segregated in veinlets, and are quite uniform in composition. The principal ore mineral is pyrite (60 to 80% of the sulphides), followed by arsenopyrite (carrying 70 to 80% of the available gold, and some other metals, as submicroscopic inclusions), with subordinate stibnite and minor amounts of other sulphides (Poltorykhin, 1974).
The productive vein and veinlet mineralisation is represented by differently aged quartz-gold-pyrite-arsenopyrite, quartz-gold-pyrite-pyrrhotite-chalcopyrite, quartz-gold-ankerite-galena-sphalerite and quartz-carbonate-chlorite associations. The first two of these associations comprise the main commercial vein, disseminated and stockwork deposits. The carbonaceous host rocks have been subjected to regional zeolite-prehnite-pumpellyite facies metamorphism; contact metamorphism and alteration that comprises weak albitisation, K-feldspar and more intensive beresitisation (feldspar alteration to a fine altered aplite like mass) and listvenitisation (coarse crystalline magnesite, quartz, talc and limonite) (Korobeinikov, 1990).
Inferred resources amounted to around 400 tonnes of contained gold at a grade of approximately 8.5 g/t Au, equating to about 47 Mt of ore in 2000.
Indicated mineral resources in December 2010 were 22.16 Mt @ 8.72 g/t Au, plus
Inferred resources of 9.67 Mt @ 7.43 g/t Au (Altynalmas Gold press release, Feb. 2011)
The most recent source geological information used to prepare this decription 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.
Bakyrchik
|
|
|
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.
|
Top | Search Again | PGC Home | Terms & Conditions
|
|
