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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[Pressure Leach Vessel]
DEPOSIT DESCRIPTIONS

MODULE 1 - AUSTRALASIA
PART B - South West Pacific Laterites,
Sun 28 May to Fri 2 June 2000

This PART  commenced on the morning of Sunday 28 May in Sydney, NSW, Australia and comprised a seminar on "New Caledonian Geology and Nickel Deposits", followed by visits to a range of the different ore styles, major and small scale operating mines and new projects under development.  An overview of the mineralisation styles visited is detailed below.
This tour was divided into three Modules and  five constituent Parts.
The other parts were Yilgarn Sulphides & Laterites, Caribbean Laterites, Canadian Sulphides & Eurasian Sulphides.



MODULE 1 - AUSTRALASIA,   PART B,   South West Pacific Laterites

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New Caledonian Silicate Nickel Laterites

The lateritic nickel ores of New Caledonia are developed over variably serpentinised peridotites (predominantly harzburgites and some dunites). Much of the ore in New Caledonia is now exposed in steep terrane, with deep erosion of the laterite/saprolite profile on the steep mountainsides. A typical profile from the SLN deposits for instance, can have up to 40 m or more of saprolite and laterite developed above bedrock. A generalised profile is capped by a few meres of iron crust (0.3% Ni, 0.01% Co, 52% Fe, 1% SiO2, 0.1% MgO), underlain progressively by 0 to 10 m thick layers of red limonite with pisolites in the upper section (0.9% Ni, 0.08% Co, 50% Fe, 1% SiO2, 0.6% MgO), yellow limonite (1.4% Ni, 0.10% Co, 49% Fe, 3% SiO2, 2% MgO), earthy ore (2 to 3% Ni, 0.15% Co, 22% Fe, 30% SiO2, 16% MgO), soft saprolite (2.3% Ni, 0.08% Co, 10% Fe, 35% SiO2, 21% MgO), ore with boulders (2.5% Ni, 0.05% Co, 12% Fe, 39% SiO2, 28% MgO), rocky ore (3% Ni, 0.02% Co, 8% Fe, 43% SiO2, 33% MgO), and fresh rock (0.3% Ni, 0.01% Co, 6% Fe, 44% SiO2, 45% MgO).

The nickeliferous saprolites of New Caledonia are principally silicate 'garnierite' ores. These silicate ores are preferentially derived from serpentinised ophiolites. Serpentinite has a higher Ni content than the olivine of the protolith. Primary serpentinisation in turn is most strongly developed in shear zones, particularly those related to the late Eocene (37 Ma) over thrusting event where structures, including serpentinite mylonites, may be several hundred metres wide. These structures control both the development of serpentinite and the depth and degree of weathering. The degree of serpentinisation in the un-weathered rock also determines the type of saprolite produced, from earthy saprolite over poorly serpentinised peridotite, to smectite rich greenish earthy saprolites on moderate serpentinisation, to 'hard' pink to green nickel rich 'garnierite' silicate saprolites from strong serpentinite development. Colour however is not indicative of grade which may only be determined by assay. The nickeliferous 'garnierite' ores are composed of three Ni-Mg sheet silicates, 1). serpentines containing the bulk of the nickel, both residual primary (lizardite) and secondary (nepouite); 2). talc (willemseite); and 3). smectite-kerolite (pimelite). Nickel is also contained in limonite derived from the direct weathering of olivine. The nickel is enriched both through leaching and from concentration of nickel into serpentine and limonite from downward migrating Ni rich aqueous solutions leached from the overlying laterites. The original 'garnierite' ores mined from 1875 and which contained the mineral garnierite, were largely depleted by the 1930's.

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New Caledonia Oxide Nickel Laterites

A number of major oxide laterite deposits are located in the south-eastern section of the island of New Caledonia. The Goro (West Prony) Project, which is the largest of these oxide laterites, is described here as an example of the deposits of the district. Goro is located near the south-eastern tip of the island of New Caledonia, approximately 45 km east of the capital Noumea. The project is operated by Goro Nickel S.A., which is 100% owned by Compagnie des Mines de Xere (CMX) registered in France which is in turn 85% owned by Inco Limited. The drill indicated resource is 165 mt @ 1.6% Ni, 0.16% Co, with an initial proven mining reserve of 47 mt. The deposit is an oxide laterite in contrast to the silicate laterites of most of the other significant mines on the island. As such it is amenable to treatment by pressure acid leach treatment, rather than the ferro-nickel and matte smelters used for the silicate ores. Goro is developed over the same peridotite mass as the other main deposits on New Caledonia. It is composed of a thick limonite and thin underlying saprolite, and occurs on a plateau with deep lateritisation, protected by an iron cap cover. It has a lower MgO and higher Co content than the silicate ores of the island. A typical profile comprises an upper thin iron cap, generally <5 m thick, overlying a limonite over burden layer that may be 15 m thick, with a zone of iron shop in its upper sections. This limonite overburden carries around 0.8 to 1.2% Ni, 0.01 to 0.06% Co, 40 to 50% Fe, 1 to 2% SiO2, 0.5 to 2% MgO. Below this zone there is more than 10 m of limonite carrying 1.2 to 1.7% Ni, 0.1 to 0.5% Co, 40 to 50% Fe, 3 to 10% SiO2, 0.6 to 3% MgO. This is followed by a transition to the saprolite, which together are less than 10 m thick. The saprolite to sap-rock carries 1.2 to +3% Ni, 0.05 to 0.5% Co, 15 to 40% Fe, 20 to 40% SiO2, 10 to 30% MgO.

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Noumea Seminar - "New Caledonian Geology and Nickel Deposits"

The seminar included presentations covering the following topics:
  • The tectonic, geologic and structural framework of New Caledonia - Pierre Maurizot, (BGRM),
  • The distribution, controls and styles of Nickel mineralisation in New Caledonia> - Pierre Charlent (INGEMINE), jointly prepared with Bernard Pelletier (SLN) & Christian Picard (UNC),
  • The nickel industry in New Caledonia - Laurent Bergeot (Director, Services des Mines et de l'Energie),
  • The regulatory regime for exploration and mining in New Caledonia - Laurent Bergeot (Director, Services des Mines et de l'Energie).
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SMGM Tomo Mine at Tontouta

The small mines of New Caledonia produce a large percentage of the nickel from the island, commonly as high grade direct shipping ore.  Tomo is one of the efficient, high grade operations visited to provide an insight into this important part of New Caledonia's nickel industry.

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SLN (Société le Nickel) Thio

Société le Nickel operates a 60 000 tpa smelter at Doniambo, near Noumea in New Caledonia which it feeds from its current four mines at Thio, Kouaoua, Népoui-Kopéto and Etoile du Nord. This facility produces both ferro-nickel and nickel matte. The smelter treats around 3 mt of ore per annum. SLN, which was formed in 1880 to mine lateritic nickel in New Caledonia is the dominant producer on the island.  It is 90% owned by the French company Eramet, which is in turn 55% owned by the French State. The lateritic ores mined by SLN are principally silicates within nickel enriched saprolites. Inclusion of established mines such as those of SLN allows access to information on well known and understood mineralisation and allows a close study of the ore, overburden and bedrock.  The Plateau Mine at Thio was visited and studied in detail.

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Falconbridge - SMSP Koniambo

Falconbridge and their local partners have completed 35000 m of drilling testing a large silicate lateritic nickel deposit in the northern half of New Caledonia. This project was included to allow an appreciation of the testing and surface expression of such deposits, and as a further very important example of the major silicate laterites of New Caledonia.

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Goro / Prony / Plaine des Lacs District

A geological tour of the Prony / Plaine des Lacs district which hosts a number of large oxide laterite deposits in south-eastern New Caledonia, including Goro and Prony (a large tested resource that is currently available for tender) which are amenable to Pressure Leach Technology.  The tour comprised a comprehensive breifing and field inspection of the Inco, Goro Project, by Inco geologists, and a field visit to the Penamax pit at Prony led by Pierre Charlent of Ingemine.

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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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LINDEN PARK 5065
South Australia
Telephone: +61 8 8379 7397
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