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Udokan

Zabaikalsky Kray, Russia

Main commodities: Cu Ag
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Udokan is a major sediment hosted copper deposit located in Zabaikalsky Kray, northeast of Lake Baikal, in eastern Russia, and ~675 km NNE of Chita, the capital of the Kray. The deposit is ~25 km SSE of Novaya Chara railway station of the Baikal-Amur Mainline (BAM) loop of the Trans-Siberian Railway, and adjacent to the Chineskaya spur line (#Location: 56° 35' 15"N, 118° 26' 57"E).

Regional Setting

Udokan is hosted by metamorphosed terriginous, deltaic to lacustrine sedimentary rocks of the Palaeoproterozoic Udokan Supergroup, that is as much as 11 to 14 km thick. This sequence was deposited within the intra cratonic, up to 300 km long Kodar-Udokan Rift Trough, also known as the South Aldan Continental Rift Zone. Unconformably underlying basement comprises Archaean granitoids and meta-sedimentary sequences of the Chara-Olekma Terrane in the western third of the Aldan Shield. The age of metamorphism of the uppermost formation in the Udokan Supergroup is constrained by an errochron of 1939 ±101 Ma (Pokrovsky and Grigoriev 1995). The rocks of the Udokan Supergroup are intruded by the roughly coeval granite of the Kodar Complex, dated at 1873 ±3 and 1877±4 Ma, and the 1867±3 Ma gabbroids of the Chiney and 1863±9 Ma Kuranakh layered mafic-ultramafic intrusive complexes. Together these intrusions represent a large scale bimodal magmatic episode (Gongalsky and Krivolutskaya, 2015) associated with the extensional regime of the Kodar-Udokan Rift Trough. The immediate Udokan deposit and host sequence are cut by widespread gabbrodolerite dykes that are interpreted to be related to the Chiney Intrusive Complex (Gongalsky and Krivolutskaya, 2015).

Gological Setting and Stratigraphy

The Udokan Supergroup comprises, from the base (Narkelyun, et al., 1970):
Kodar Group, 1200 m thick - dark grey to black bedded shales and phyllites grading up into grey to lilac siltstones and sandstones with abundant pyrrhotite and pyrite, deposited in an environment that range from deep marine in the lower part of the sequence to littoral in the overlying upper formation. It is subdivided into the:
  Ikabia Formation, which is 1000 to 1500 m thick and is characterised by dark grey mica schist, locally containing abundant pyrrhotite and pyrite (Zientek et al., 2010);
  Ayan Formation, ~100 to 1100 m of thin, alternating dark grey to grey silty sandstone, siltstone and shale, with many carbonate-bearing beds. Ripple marks occur on bedding planes in the east of the basin (Zientek et al., 2010);
Chiney Group, up to 3000 m thick - pink, green and grey sandstones with some conglomerates near the base, with intercalated but lesser siltstones and argillites and some carbonates (marls, stromatolitic dolomites and limestone) from the middle upwards. Ripple marks, cross bedding and desiccation cracks increase from the centre towards the top. Sparse pyrite and some copper mineralisation is found in the carbonates. It is subdivided into the:
  Inyr Formation, ~600 to 800 m of fine-grained, grey arkosic to pure quartz sandstone with beds of black siltstone. Quartzose gravel beds occur locally at the base (Bogdanov et al., 1966);
  Chitkanda Formation, further subdivided into a:
  • Lower Member, comprising 400 to 500 m of fine-grained arkosic sandstone, commonly with carbonate cement, siltstone and shale. Stratification is horizontal to wavy, although wavy cross- to finely cross-stratified rocks with ripple marks are also present;
  • Upper Member that is ~400 to 800 m thick and is composed of light-coloured arkosic sandstone interbedded with thin-bedded black shale. Wavy stratification to wavy cross-stratification, locally enhanced by magnetite partings, is characteristic; ripple marks and mud cracks are also observed. Sandstones of this member have high sodium content, interpreted to suggest the presence of tuffaceous material (Podkovyrov et al., 2006).
  Aleksandrov Formation, an ~400 to 550 m thick alternating sequence of thin siltstone, shale, silty sandstone, marl and dolomite (Bogdanov et al., 1966). In the eastern part of the Kodar-Udokan Trough, the bedding planes show numerous ripple marks, mud cracks and turbidite structures, whereas horizontal stratification is predominant in the south and west;
  Butun Formation, ~1000 to 1500 m of alternating siltstone, shale, limestone and dolomite (Bogdanov et al., 1966). In the northeastern part of the Kodar-Udokan Trough, the rocks are altered to lilac grey albitite that shows only a vestige of original stratification. Carbonate rocks become more abundant to the west (Zientek et al., 2010).
Kemen Group, up to 4000 m thick - which unconformably overlies the Chiney Group, comprises the:
  Talakan Formation, which is 800 to 1500 m thick and is composed of fine-grained, mainly arkosic sandstone, siltstone and shale, that is horizontally to wavy- and finely cross-stratified (Bogdanov et al., 1966) and contains cupriferous sandstone and siltstone units;
  Sakukan Formation, which exhibits cross bedding, ripple marks, desiccation cracks, mud rolls and scour structures. It is divided into three sub-formations by Gongalsky and Krivolutskaya (2015) after Krendelev et al. (1983), although (Zientek et al., 2010) only recognise a Lower and an Upper Sub-formation;
  Lower Sub-formation, that is 1300 to 1800 m thick and consists of fine- to medium-grained, cross-bedded arkosic sandstone in which horizontal stratification is uncommon. Magnetite partings enhance stratification and are characteristic. Floating pebbles (dropstones ?) of intrusive, volcanic and metamorphic rocks are found near the base (Burmistrov, 1990). The unit is interpreted to have formed by longshore and bottom shelf currents and to a lesser degree, by storm surges and may represent a marine molasse deposit (Burmistrov, 1990).
  Middle Sub-formation, which is 1300 to 1800 m thick and includes magnetite-bearing sandstones and pebble conglomerates.
  Upper Sub-formation, that is 600 to 1100 m thick, and consists of fine-grained, more or less arkosic sandstone, accompanied by siltstone and shale (Bogdanov et al., 1966). A typical feature is the presence of calcite-cemented lenticular sandstone with shale fragments. The stratification varies from cross to wavy and horizontal, with ripple marks and mud cracks. The Upper Sakukan strata form fining-upward sequences typical of coastal-marine, subaqueous-delta, and terrestrial-delta environments (Burmistrov, 1990). The Udokan copper mineralisation is developed in the middle part of this unit, which has been split into the following members:
  • Sub ore Member, 250 m thick - grey and pinkish grey, fine and medium grained, cross bedded, quartz feldspar sandstone, with a sericite, quartz and calcite matrix. Numerous lensoid cross bedded calcareous sandstones from 0.05 to 1.5 m thick occur at 1 to 5 m intervals and characterise this unit. Extremely lean copper sulphides are present.
  • Ore Member, 20 to 300 m thick - this member is characterised by its complex facies relationships. The sandstones are commonly cross bedded in the lower sections and the siltstone laminae exhibit ripple marks and desiccation cracks. Layer and lens like ore bearing units are distributed in an en echelon fashion. Stratabound copper-bearing units within the ore member vary from 2 to 113 m in thickness. The individual ore bearing units are composed of claystone, siltstone, silty sandstone, sandy limestone and conglomeratic breccia, with intricate mutual transitions seen both laterally and down dip (Chechetkin et al., 2000). They comprise rhythmically repeating beds (from bottom to top) of conglomeratic breccia → sandstone → siltstone. Grey, fine to medium and mixed grain size quartz sandstone constitutes >90% of the ore host, whereas clayey rocks collectively account for no more than 3 to 5%. The sandstone is dominantly composed of mildly calcareous and non-calcareous facies, with <40% of the ore by volume in the sandstone with calcareous cement, and carbonate beds are rare. Quartz sandstone is fine- to medium-grained, grey and is not equigranular. In addition to the dominant clastic quartz grains, it contains abundant fragments of albite-oligoclase, saussuritised plagioclase, microcline, quartzite, micropegmatite and felsic volcanic rocks. Accessory minerals are magnetite, titanomagnetite, ilmenite, zircon, tourmaline, apatite, hematite and titanite. In the sandstone, the clastic grains are dominantly set in a cement of sericite and quartz, <10% of which is calcareous. Calcareous medium-grained and noncalcareous fine-grained and equigranular sandstone dominate in the lower part of the sequence, occurring as ~2.5 m layers and lenses that are <300 m in lateral extent. Fine-grained, non-equigranular quartz sandstone is widespread in the upper part of the member and is the typical host to copper mineralisation at Udokan, and include on their peripheries, fused light grey rocks with clastic grains often cemented by chalcocite and bornite. All sandstone facies have cross and wavy bedding, although cross-bedded rocks are predominantly localised in the lower part of this section.This member contains all of the economic mineralisation in the Udokan deposit.
  • Supra Ore Member, 100 m thick - light grey and pinkish grey, predominantly fine grained, horizontally and wavy bedded, quartz-feldspar sandstones and less frequently siltstones. No copper is present.
  Naminga Formation, which is 1000 to 1600 m thick, and is composed of dark grey to black shallow water siltstones and argillites with intercalated pink to grey sandstone. This group contains sparse magnetite. Ripple marks and mudcracks are common on bedding surfaces (Volodin et al., 1994). These sedimentary rocks most likely accumulated in shallow-water bays, lagoons, and lakes (Burmistrov, 1990).

Stromatolitic species that resemble those of the Riphean (1600 to 800 Ma) and medusoid imprints (Udokania Problematica) interpreted to resemble Ediacaran (Vendian) fauna (Burmistrov, 1993) have been found in different metasedimentary units of the Kemen Group, and have been interpreted to indicate that group is of Neoproterozoic age (Gablina and Malinovksii, 2008). If this were the case, it would require the group to be an allochthonous thrust slice overlying the Chiney Group, and would necessitiate the contact with Palaeoproterozoic intrusions to be re-examined and reinterpreted. Similarly, the dropstones in the Lower Sakukan Subformation could be equivalent to those in other Neoprotereozoic glacial sequences, e.g., in the Central African Copperbelt (Burmistrov, 1993)

Udokan
Geological map and cross section of the Udokan deposit (Soloviev, 2010, after Krendelev et al., 1983; Chechetkin et al., 2000, Smirnov, 1978, Bakun et al., 1966).


Mineralisation

Ore and sub-ore grade copper mineralisation occupies most of the extent of the Ore Member of the Sakukan Formagtion throughout the Naminga Syncline. Similar cupriferous units are found in the stratigraphic equivalents in adjacent areas over a strike length of several hundred kilometres around Udokan. Copper deposits and occurrences are also known within all three groups of the Udokan Supergroup, but mostly in the uppermost Kemen Group (Sakukan and Naminga Formations) and the underlying middle part of the Chiney Group in the Udokan area. The copper in the Chiney Group is accompanied by rare earth minerals (Narkelyun, et al., 1970; Smirnov, 1977; Gongalsky and Krivolutskaya, 2015). Numerous pyrrhotite- and chalcopyrite-bearing units, containing Ag, Co and Ni are hosted in the lower formations of the Kodar Group (Bogdanov et al., 1966; Arkhangel'skaya et al., 2004).

Copper mineralisation at Udokan occupies a 25 to 30 x 12 km synformal outlier, part of the regional Naminga Syncline. The rocks of the northern, eastern and western limbs dip towards the centre of the structure at from 10 to 12°, up to 35 to 40°. On the southern limb however, the fold is more complex, overturned with dips varying from 25 to 30°S in its western section, to as much as 45 to 50°SSW in the central and eastern parts. In the centre of the fold, at a depth of ~1.5 km, the mineralised beds are flat lying. The attitude of the limbs of the fold are complicated by small second order folds as well as small concordant and discordant crush zones, faults and thrusts with displacements of 0.1 to 15 m, accompanied by zones of intense jointing. Within the syncline, the Udokan Supergroup is cut by numerous dykes associated with various intrusive complexes. The most widespread are gabbro-dolerite dykes with thicknesses in some cases of up to 150 m or more. Adjacent to these dykes the sedimentary rocks are often strongly contact metamorphosed, with Cu being upgraded and the mineralogy modified from bornite-chalcocite to bornite and to chalcopyrite as the dyke is approached (Smirnov, 1977).

The ore-bearing units have been traced for 25 km along the current perimeter of the Naminga syncline in the Udokan outlier. Four ore-bearing position have been recognised in the vertical sequence (Chechetkin et al., 1995), labeled as 0, I, II and III with thicknesses that vary from 50 to 270 m. Within these, 53 separate orebodies have been outlined, which typically have strike lengths of from 300 to 2000 m, down-dip extents of from 400 to 2500 m and thicknesses of 16 to 52 m. Individual orebodies vary in shape from tabular and lenticular to ribbonlike. The orebodies thin on their margins where they split into a series of fingers. Compared to the northern limb, their thickness is markedly reduced on the southern limb (Gongalsky and Krivolutskaya, 2015).

Three main hypogene ore-sulphide assemblages are differentiated, namely, i). pyrite-chalcopyrite; ii). chalcopyrite-bornite; and iii). bornite-chalcocite. There is a mineral zonation within the deposit that correlates with the host lithologies. Bornite-chalcocite is usually found within coarser deltaic facies, while chalcopyrite-pyrite occurs in finer, deeper water facies. Bornite-chalcocite ore dominates on the northern limb of the syncline, with the ratio of the thickness of pyrite-chalcopyrite to bornite-chalcocite ore varying from 1:2 to 1:20. Southward, down dip, toward the hinge of the syncline, the amount of bornite-chalcocite mineralisation decreases, while the quantity of pyrite-chalcopyrite increases. On the southern limb, the proportion of bornite-chalcocite ore increases again, although the ratio of pyrite-chalcopyrite to bornite-chalcocite only reaches 1:1 to 1:3. Within the Cu-bearing sequence at the northern limb of the syncline, there is a stratigraphic upward zonation from pyrite-chalcopyrite to a bornite-chalcocite assemblage. A symmetric zonation occurs in the axis of the syncline, where the centre of the mineralised zone or unit is composed of predominantly pyrite, which transitions to pyrite-chalcopyrite → bornite-chalcocite mineralisation at both the base and top of the mineralised zone. On the southern limb, an inverse zoning is recorded, where, in contrast to the northern limb, the pyrite-chalcopyrite ore occurs at the stratigraphic top (but structural bottom) of the lode and the bornite-chalcocite assemblage is stratigraphically below (Gongalsky and Krivolutskaya, 2015).

Within the bornite-chalcocite assemblage ores, bornite and chalcocite always occur in association with magnetite. Chalcocite rims bornite grains, whose morphology changes, depending upon available interstitial space. Veinlets and veins of chalcocite-bornite are also mostly oriented conformably to the bedding. Among the rare minerals, native silver and carrollite are most frequently identified. Iron oxides, predominantly magnetite, and iron sulphides occur in several orebodies. The magnetite content in the disseminated and massive chalcocite-magnetite mineralisation assemblages is frequently as high as 50 vol.%, averaging 10 to 15 vol.%. Magnetite occurs as round grains and euhedral crystals, which are interpreted to either be products of recrystallisation due to superimposed hydrothermal alteration (Gablina and Ermilov 1990) or a hydrothermal mineral. Magnetite is often martitised with the relict magnetite grain forming a core, surrounded by hematite rims (Gongalsky and Krivolutskaya, 2015).

Light δ
34S isotopes in the hypogene mineralisation were measured between -20 to -24‰, to as much as -27‰ by (Gongalsky and Krivolutskaya, 2015). This is interpreted to suggest biogenic sulphate reduction for the sulphur. This may imply an original diagenetic pyrite deposited within the Ore Member that acted as a reductant nuclei for later introduction of post-depositional Cu in oxidised solution to convert pyrite to chalcopyrite, bornite and chalcocite as is common in sediment hosted copper deposits (e.g., White Pine in the US.)

The ore has been oxidised with a 'wide distribution' of supergene malachite, azurite, covellite, chalcocite, gypsum and iron hydroxides, such that currently the deposit is composed of 67.5% chalcocite-bornite, 6.5% chalcopyrite and 26.0% malachite-brochantite (Arkhangel'skaya et al., 2004; Volodin et al., 1994; Chechetkin et al., 2000). The ores of the Udokan deposit also contain Ni, Co, Zn, Mo, and other trace elements in addition to the main Cu-Ag-Fe components. Below the base of oxidation, the sulphide ore, 65% of copper is contained in chalcocite, 20 to 25% in bornite, and 10 to 15% in chalcopyrite. In addition to these major copper minerals, magnetite is widespread, as are pyrite and hematite, whilst valleriite, molybdenite, wittichenite, pyrrhotite, sphalerite, marcasite, tennantite, polydymite, cobaltite, stromeyerite, native silver, and native gold are recognised, but rare (Gongalsky and Krivolutskaya, 2015).

Where exposed, the outcrop of the copper bearing horizon is characterised by 'crusts and earthy friable accumulations of a green colour, consisting of malachite, bronchantite and other minerals of the oxidation zone'. Moreover ore seams have been recorded on the surface with only weakly oxidised sulphides (Smirnov, 1977). However, Gongalsky and Krivolutskaya (2015) note that oxidised and mixed ore constitute ~50% of total ore in the deposit. Iron hydroxides are widely distributed near the surface as 'scabs', crusts, veinlets and oolitic aggregates in cracks in outcropping mineralisation, and in faults. These include goethite, hydrogoethite, hydrohematite and lepidocrocite. Goethite substitutes for chalcopyrite, while hydrogoethite is present among oxidised bornite aggregates. Other supergene minerals in the oxide and mixed zone include, in order of significance, sulphates, carbonates, Fe-oxides, and silicates. Brochantite is the most important sulphate. It forms pseudomorphs after malachite and azurite and is altered to chrysocolla. Other less abundant sulphates are antlerite, chalcanthite, gypsum, melanterite, halotrichite, jarosite and dolerophanite. Carbonates, which are mainly developed in mineralised calcareous sandstone hosts, and include malachite, azurite and rare cerussite. Other supergene oxide minerals below the surface include psilomelane; cuprite after bornite-chalcocite but never after pyrite-chalcopyrite; tenorite that is found as a pulverulent black mass, smears and incrustations in cavities and fine cracks in pyrite-chalcopyrite mineralisation. The principal silicate is chrysocolla, which is rare and only locally developed. Secondary sulphides include chalcocite which is blue black to grey and forms pseudomorphs after bornite and chalcopyrite, and can be differentiated from hypogene chalcocite which is white; indigo-blue massive metallic covellite usually forms after chalcocite and bornite and to a lesser degree, chalcopyrite. Supergene bornite is rare, rimming chalcopyrite and is red to purple in colour; whilst similarly rare supergen chalcopyrite may rim chalcocite. Secondary native copper is usually located on the surface in association with cuprite and iron oxides, but may also occur at depth in some instances (Gongalsky and Krivolutskaya, 2015).

Within higher grade sections of the ore member, in addition to the disseminated sulphides, fine sulphide, quartz and quartz-sulphide veins are also developed, which may be a few cm to as much as 30 cm thick and persist over lengths of up to 20 m (Smirnov, 1978). Krendelev et al. (1983) recognized four types of bedding-parallel and crosscutting quartz-carbonate veinlets with chalcocite-bornite mineralisation. Quartz-sulphide veinlets are rimmed with metasomatic magnetite, which differs in morphology and composition from the magnetite in the sedimentary laminae. These veinlets carry up to 0.3 ppm Au, whereas the gold grade in the barren sandstone does not exceed 0.01 ppm. In addition to the crosscutting quartz-carbonate-sulphide veins, which have been widely documented, stratabound and crosscutting veins, complex in structure, often brecciated and with large sulphide segregations, are widespread in the upper part of the productive sequence. The brecciated, near bedding parallel veins contain fragments of quartz and host rocks (Petrovsky, 1985, 2003). Thick zones composed of a few tens of metres of brecciated host sandstone and claystone have also been outlined, cemented by gangue quartz with chalcocite, bornite and chalcopyrite. Similarly, fragments of host rocks and gangue quartz are cemented in central parts of the veins with coarse crystalline bornite and, to a lesser extent, by chalcocite. Sulphides within the matrix of breccia zones often penetrate into the zone of finely disseminated chalcocite ore, which, in turn, gives way to the zone of magnetite disseminations. The bedding-parallel and crosscutting sulphide and quartz-sulphide veins, together with the adjacent country rocks, are characterised by a zonation whereby coarsely-crystalline bornite which is dominant in the veins, has been replaced by chalcocite-group minerals along grain margins and along fractures. This zone passes out into finely disseminated chalcocite with much less bornite; and then to an outer zone containing magnetite disseminations (Gongalsky and Krivolutskaya, 2015).

The isotopic age of the sedimentary rocks at Udokan is constrained to 1980 to 1832 Ma (K-Ar; Chechetkin and Kharitonov 2002). Perelló et al. (2017) separated titanite crystals from a sample collected in the Medny orebody (north-western) section of the deposit, where typical high-grade disseminated and veinlet chalcocite-bornite mineralisation is well exposed. Titanite crystals from the disseminated and veinlet fractions were separately dated (ID-TIMS, U-Pb), with the disseminated fraction returning a concordia age of 1895.3 ±9.7 Ma whilst the veinlet fraction yielded a concordia age of 1896.7 ±7.8 Ma. The combination of both titanite fractions produced a concordia age of 1896.2 ±6.2 Ma, interpreted as synorogenic mineralisation (see age of metamorphism above; Gongalsky and Krivolutskaya, 2015).

As detailed previously, the Udokan deposit is located within section of the regional Naminga Syncline, flanked to the immediate south by the Chiney Anticline, a large domal antiformal structure, the core of which is occupied by the ~120 km
2 Chiney layered mafic-ultramafic intrusive complex. This complex is exposed ~10 km to the SSE of Udokan, although Konnikov (1986) suggested a northern continuation may have been down-faulted by the structure that defines its current northern exposed margin, to lie 3 to 5 km beneath the Udokan copper deposit. Furthermore, 3D modelling of gravity data suggests the Chiney Intrusive Complex is developed above a much larger deep magma chamber that extends to depths of >20 km. The multiple and diachronous injections of mafic melt phases that make up the Chiney Intrusive Complex suggests it is the result of repeated tapping of the deep, differentiating magma chamber. The Chiney Intrusive Complex hosts both extensive cumulate Fe-Ti-V mineralisation as titanomagnetite in its lower half, and cumulate copper mineralisation at the base of the intrusion (e.g., of the latter is Kontaktovyi), with stratabound disseminated and vein copper sulphides in the underlying meta-sedimentary rocks of the Udokan Supergroup (e.g., at Rudnoe). However, at deposits such as Pravoingamakitskoe, sediment hosted disseminated, massive and veined sulphide mineralisation is restricted to sandstones of the Chitkanda and Alexandrov formations that belong to the Chiney Group, which underlies the Kemen Group hosting Udokan. This mineralisation has been traced along host units within this sequence for as much as 4 km from their contact with the Chiney Intrusive Complex. These deposits, as described in the Chiney Intrusive Complex record, suggest a transition from magmatic cumulate to hydrothermal stratabound mineralisation (Gongalsky and Krivolutskaya, 2015). While sediment hosted exocontact mineralisation at Rudnoe, and stratabound massive, disseminated and veined sulphides at Pravoingamakitskoe and at Udokan are all similar in that they are sediment hosted Cu-Ag mineralisation, they differ markedly in stratigraphic position, mineralogy and chemical characteristics. However, as detailed above Udokan is one of a number of Cu-Ag deposits and a large number of occurrences developed over strike lengths of several hundred kilometres within the same host unit, but also at other stratigraphic positions throughout the Udokan Supergroup in the Kodar and Chiney Groups. This amount and spread of copper, including the potential 27 Mt of contained Cu metal inferred in the Udokan deposit (see below) and 50 Mt in the district as a whole (Gongalsky and Krivolutskaya, 2015), would require a large source supplying metal to a considerable volume of Udokan Supergroup. While basinal fluids may have leached Cu from the Udokan Supergroup, another possibility is a mantle input, such as the large, differentiating deep magma chamber below the Chiney Intrusive Complex and other similar intrusions in the Kodar-Udokan Rift Trough that were active during the period of hydrothermal mineralisation at Udokan. It is envisaged the deep magma chamber differentiated both Cu-rich magmatic cumulate melts and hydrothermal fluid fractions rich in Cu. The former physically formed the Chiney Intrusive Complex, while the latter were potentially released into the sedimentary pile to mix with basinal fluids and be transported to sites of deposition and reaction with sulphur. The differences in mineralogy and chemistry between the examples noted above would be a reflection of the source-release (i.e., magmatic or hydrothermal), transport, sulphur source, host lithology and deposition process in each case. Alternatively, the same deep magma chamber, once cooled and crystallised could act as a Cu source to be leached by basinal and/or metamorphic fluids.

Published JORC compliant resources as of March 2014 (Baikal Mining Company website - viewed December, 2020) are:
    Measured Mineral Resource - 339 Mt @ 1.03% Cu, 8.9 g/t Ag;
    Indicated Mineral Resource - 1483 Mt @ 1.01% Cu, 11.1 g/t Ag;
    Inferred Mineral Resource - 932 Mt @ 0.89% Cu, 14.3 g/t Ag;
  TOTAL Mineral Resource - 2.754 Gt @ 0.97% Cu, 11.9 g/t Ag;
    Proved Ore Reserve - 292 Mt @ 1.04% Cu, 8.9 g/t Ag;
    Proved Ore Reserve - 1147.5 Mt @ 1.05% Cu, 11.2 g/t Ag;
  TOTAL Ore Reserve - 1.4395 Gt @ 1.05% Cu, 10.8 g/t Ag (included in Mineral Resources).

According to the estimation data, economic reserves of Russian categories В+С1 = 16.864 Mt of contained copper; Category С2 = 3.232 Mt of copper and 17 119 t of silver; whilst sub-economic reserves of categories С1+С2 = 0.953 Mt of copper and 1012 t of silver. The resource potential of Udokan deposit is estimated at more than 27 Mt of copper, as of March 2014 (Baikal Mining Company website - viewed December, 2020).

The most recent source geological information used to prepare this summary was dated: 2015.     Record last updated: 3/1/2021
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.


Udokan

  References & Additional Information
   Selected References:
Gongalsky, B. and Krivolutskaya, N.,  2019 - The Cu-Ag-Fe Udokan Deposit: in Gongalsky, B. and Krivolutskaya, N., 2019 World-Class Mineral Deposits of Northeastern Transbaikalia, Siberia, Russia, Modern Approaches in Solid Earth Sciences, Springer, Switzerland,   v.17, Ch. 3, pp. 37-85.
Hitzman, M.W., Selley, D. and Bull, S.,  2010 - Formation of Sedimentary Rock-Hosted Stratiform Copper Deposits through Earth History : in    Econ. Geol.   v.105, pp. 627-639.
Podkovyrov, V.N., Kotov, A.B., Larin, A.M., Kotova, L.N., Kovach, V.P. and Zagornaya, N.Yu.,  2006 - Sources and Provenances of Lower Proterozoic Terrigenous Rocks of the Udokan Group, Southern Kodar-Udokan Depression: Results of Sm-Nd Isotopic Investigations: in    Doklady Earth Sciences,   v.408, pp. 518-522.
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.
Soloviev, S.G.,  2010 - Iron Oxide Copper-Gold and Related Mineralisation of Siberian Craton, Russia 2 - Iron Oxide, Copper, Gold and Uranium Deposits of the Aldan Shield, South-Eastern Siberia: in Porter, T.M., (Ed.),  2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.4, pp. 515-534.
Zientek M L, Hayes T S and Hammarstrom J M  2013 - Overview of a New Descriptive Model for Sediment- Hosted Stratabound Copper Deposits: in Zientek M L, Hammarstrom J M and Johnson K M, 2013 Descriptive Models, Grade-Tonnage Relations, and Databases for the Assessment of Sediment-Hosted Copper Deposits - With Emphasis on Deposits in the Central African Copperbelt, Democratic Republic of the Congo and Zambia USGS Scientific Investigations,   Report 2010-5090-J pp. 2-16


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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