An AMF-PGC International Study Tour
Developed & Managed by Porter GeoConsultancy
Nickel 2000
The Major Nickel Deposits of the World
May-June 2000
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[Noril'sk Smelter]
DEPOSIT DESCRIPTIONS

MODULE 3 - EURASIA
Mon 19 to Wed 28 June 2000

This MODULE commenced in Moscow, Russia on the evening of Monday 19 June, 2000 and included visits to:
  • Noril'sk - Talnakh, Russia - Immense deposit associated with Permo-Triassic sills
  • Jinchuan, Gansu - China - Large deposit in a Proterozoic dyke
This tour was divided into three Modules and  five constituent Parts.
The other parts are Yilgarn Sulphides & Laterites, SW Pacific Laterites, Caribbean Laterites, Canadian Sulphides.



MODULE 3 - EURASIA, Eurasian Sulphides

Noril'sk - Talnakh - Siberia Russia

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The Permo-Triassic Noril'sk - Talnakh groups of deposits of Siberia, northern Russia are 35 km apart and are developed near the north-western margin of the Siberian Platform. The deposits are found within and adjacent to gabbro-dolerite sills that represent part of the feeder zone of the up to 3500 m thick, vast Permo-Triassic Siberian trap basalts. The basement to the Siberian Platform is composed of crystalline Proterozoic rocks overlain by late Proterozoic sediments, l ower Palaeozoic marine dolomites, argillites and sandstones, and by Devonian marls and evaporites. These are followed by Carboniferous shallow water limestones, continental sediments and coal measures. The Palaeozoic sequence is around 6000 m thick. The host sills are developed within and adjacent to the continental scale, NNE trending Noril'sk-Kharayelakh fault. These ore bearing sill like intrusive bodies have known dimensions of as much as 15x0.5 to 2 km and are from 50 to 300 m in thickness, although they only represent 1 to 2% of the total mafic intrusives in the district. A typical sill is said to consist of a lower olivine bearing, melanocratic gabbro-dolerite with a picritic composition, passing upwards into leucocratic gabbro-dolerites near the top. This has been variously interpreted to result from differentiation or from multiple intrusive pulses. On both the upper and lower margins there are zones of taxite containing increased sulphides, platinoids and chromite. A taxite is a mafic igneous rock with a very variable texture (from fine to pegmatitic) - and composition (leucocratic to melanocratic) - with discrete ghost-like remnants of inclusions of other gabbroic and country rocks. The upper zone is more weakly taxitic. A strong hornfels halo extends for 100 m below the sills and up to 250 m above. There are three main ore types developed at Noril'sk and Talnakh. These are: 1). Disseminated sulphides within the differentiated gabbro-dolerite sills, principally on the lower margins of the mineralised sills in the taxitic and to a lesser degree the picritic zones. They occur as droplets, schleiren and fine sulphide veinlets, forming sheet like conformable bodies up to 40 m thick and comprise combinations of chalcopyrite, cubanite and pyrrhotite with troilite and pentlandite. Grades average 0.5 to 0.6% Ni, 0.6 to 0.7% Cu, and 5 to 6 g/t PGE; 2). Massive sulphides found principally on the lower contact of the mineralised sills, both within the enclosing rocks and to a lesser degree the sill, and are often separated from the sill by several metres of barren sediment or cupriferous mineralisation. Sometimes they are also found on the upper margin of the sill. In other locations the massive sulphides cut across the sill to its upper margins. The massive sulphides are divided into either pyrrhotite, cubanite or chalcopyrite types, depending on the dominant sulphide, with associated pentlandite moihoekite and talnakhite. Individual massive sulphide bodies may be up to 60 m thick as at Oktyabr'sky where it cover an area of 3.5 km2. Grades vary drastically with the sulphide assemblage, but are of the order of 2.8% Ni, 5.6% Cu and 15 g/t PGE. There is evidence that the massive sulphides post date the disseminated sulphides; and 3). Vein disseminations of 'cupriferous' ore which are found below the massive sulphide, between the massive sulphide and the lower margins of the sill, and within sediments on the upper margin of the sill, often associated with zones of 'skarn' altered brecciated dolerite and marl/argillite. They may be 10 to 20m thick. The main metallic minerals are pyrrhotite, pentlandite, chalcopyrite, cubanite, millerite, pyrite, magnetite, bornite, chalcocite, etc.

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Jinchuan - Gansu China

The Jinchuan nickel complex is located in Gansu Province, some 1200 km to the west of Beijing. It lies on the south-western margin of the North China Platform, and the underlying Sino-Korean Craton, near the margin with the adjacent Qinling Fold Belt to the south-west. It lies within a north-west trending, uplifted terrane of Middle Proterozoic migmatites, biotite gneisses and marbles, bounded on both sides by two regional faults. Proterozoic mafic-ultramafic intrusions are found within the terrane, mainly along these two faults. The Jinchuan Intrusion, which hosts the Ni-Cu deposits, is found on the northern margin of the terrane and has been dated at 1510 Ma. It comprises a north-west elongated body, some 6 km long and 300 m wide. The Ni-Cu ores at Jinchuan are based on a 0.5% Ni cut-off. Numerous ore lenses have been defined, mainly in the lower part of the igneous mass. Most are very small, although three large bodies have been recognised, namely Orebodies 24, 1 and 2 which account for about 90% of the known resources. Orebody 24 lies within the western of three magma sub-chambers. The strike length of the sub-chamber, which lenses out on each extremity, is around 2100 m, with a maximum width and depth of 300 and 600 m respectively. The chamber has a central core of dunite and olivine rich peridotite, 50 to 100 m thick (lensing out at depth and towards the surface), bounded on both sides by lherzolite, and an outer thin discontinuous skin up to 30 m thick of olivine-websterite pyroxenite. Orebody 24 is a tabular shaped mass sub-parallel to the walls of, and with roughly the same length as the sub-chamber. It has a width of 100 to 200 m. All of the intrusive rock types, except the pyroxenite host sulphides. The largest mass of ore, Orebody 1, falls within the West-Central sub-chamber, the second of the three identified. This chamber has a length of 1700 m, width of around 300 m and depth extent of 500 to 1000 m. The distribution of lithologies and ore is similar to that of the West Sub-Chamber and Orebody 24, except that the main high grade dunite core is thicker. The orebody has dimension of 1500 m long, 150 m wide and extends from 200 to 1100 m down dip. The East Sub-chamber is wider and shallower, with a trumpet shaped cross section and a width of up to 530 m at surface. Orebody 2 is located at the base of the sub-chamber and is 1300 m long and 120 m wide. Four ore types are recognised at Jinchuan, namely: 1). net-textured sulphides, the dominant ore, which comprise sulphides filling the interstitial voids of the olivine cumulates, with grades of 1 to 4% Ni - usually forming lensoid bodies in the core and lower sections of the ore zone, and in Orebodies 24 and 1 grades outwards into disseminated ore; 2). disseminated sulphides comprise that part of the orebody where net-textured sulphides do not form a continuous network, and usually has a grade of <1% Ni, occurring as small lenses on the upper sections, ends or flanks of the ore zones; 3). massive sulphide ore is only present in 2 Orebody where it carries 4 to 9% Ni , occurring as aggregates or irregular up to 5 m thick veins parallel to the main ore zone - commonly occurring with gradational boundaries within the net-textured ore zones - the veins often contain xenoliths of sediment and may form a breccia type ore; and 4). metasomatic ore on the contact of the intrusive and marbles. The principal minerals are pyrrhotite (dominant), pentlandite (violarite), chalcopyrite, cubanite, mackinawite and pyrite. The Jinchuan complex contains in excess of 500 mt @ 1.25% Ni, 0.8% Cu, 0.34% Co, about 1 g/t (Au+PGE). Production commenced in 1963, with a total in excess of 50 mt having been mined to date. In 1990 the output was 27 300 t of contained Ni from 3.8 mt pa of ore. The mine currently produces around 40 000 t of contained Ni per annum.

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For more information contact:   T M (Mike) Porter, of Porter GeoConsultancy   (mike.porter@portergeo.com.au)

This was another of the International Study Tours designed, developed, organised and escorted by T M (Mike) Porter of Porter GeoConsultancy Pty Ltd (PGC) in joint venture with the Australian Mineral Foundation (AMF).  While the reputation and support of the AMF contributed to the establishment of the tours, after it ceased trading at the end of 2001, PGC has continued to develop, organise and manage the tour series.

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