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New Caledonia : Geology and Mining
Chapter · January 2007
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Pirard Cassian Research School of Earth Sciences The Australian National University
Table of Contents
Executive Summary……………………………………………………………………. 3
1.0. Overview of New Caledonia………………………………………………………. 4
1.1. Geography…………………………………………………………………. 4
1.2. Climate and Ecology………………………………………………………. 5
1.3. History, demography and politics…………………………………………. 6
1.4. Economy…………………………………………………………………… 7
2.0. Geology……………………………………………………………………………. 9
2.1. Regional geological settings………………………………………………. 9
2.2. General tectonics…………………………………………………………... 1
2.3. Terranes of New Caledonia………………………………………………... 1
2.3.1. Ante-Senonian basement……………………………………….. 1
2.3.2. High pressure rocks…………………………………………….. 1
2.3.3. Obduction nappes………………………………………………. 2
2.3.4. Post-obduction rocks…………………………………………… 2
3.0. Mining in New Caledonia…………………………………………………………. 3
3.1. Major Past and current extracted products……………………………. 3
3.2. Minor exploitations…………………………………………………… 4
3.3. Subeconomic enrichments……………………………………………. 4
3.4. Non-metal resources…………………………………………………... 5
0
1
2
7
3
9
3
5
6
9
4.0. References…………………………………………………………………………. 5
2
3
2
Executive Summary
New Caledonia is an island of the south-western Pacific Ocean which belongs
to France. This island has a long geological history which goes back to the break up
of Gondwana during the Mesozoic. The succession of large scale events including
accretion, subduction and obduction has formed 4 main groups of rocks in New
Caledonia. The Ante-Senonian basement is the accretion of oceanic terrane on the
eastern margin of Gondwana from Permian to Late Jurassic. Subduction processes are
the main feature of the northern terranes which show high pressure metamorphism
from shallow zone to blueschists and eclogite facies. In the same time, obduction of
oceanic crust on New Caledonia continent has created the main feature of the island’s
geology with large ultramafic massifs underlying nearly half of New Caledonia
surface area. The last group of rock occurring after the subduction and obduction
events is mainly characterized by sedimentary rocks and important tropical alteration
processes of the older rocks.
This complex geological history provides the basis for the formation of ore
deposits. The most remarkable feature of New Caledonia mining landscape is nickel
laterite. These ores cover most of the ultramafic terranes and have been exploited for
decades. New projects are underway in Goro and Koniambo areas which will re-
establish New Caledonia as one of the biggest producers of nickel in the world.
Cobalt and chromium are also by-products of the ultramafic terrane exploitation.
Other deposits are more limited in size such as Cu-Zn-Pb-Ag mineralization in the
Diahot area and occurrences of platinoids and gold appear to be uneconomic. Minor
occurrences of iron ores, coal and manganese are known.
The institutional arrangements in New Caledonia, particularly the Geological
Survey, provide basic information on the geology and mineral resources of the island.
3
1.0. Overview of New Caledonia
1.1. Geography
New Caledonia is an archipelago composed of several islands (Loyalty
Islands, Belep Islands, Ile des Pins, Grande Terre), reefs and lagoons located in the
western Pacific Ocean. It lies approximately 1500km east of Australia, 2000km north
of New Zealand and just south of Vanuatu (Fig. 1).
Grande Terre (translation. : large land), the main island, forms more than 80%
of the New Caledonia surface area and is an elongated island nearly 400km long and
over 40km wide. The name New Caledonia is often considered as a synonym of
Grande Terre and the minor islands are only significant at a local scale. Grande Terre
is the only mountainous island in the area with Mount Panié (1628m) and Mount
Humboldt (1610m) the highest points. Mountains form a continuous chain across the
island, steep on the east coast and forming numerous rias, whereas the west has low
and swampy coastal plains between hilly massifs (Paris, 1981). Most of the rivers are
transversal to the central ridge and run down in those lowlands and mangrove finally
entering in the lagoon which rims the entire island.
Fig.1. New Caledonia in the south western Pacific Ocean (Cluzel et al., 2001).
4
The lagoon is one of the largest and most diverse in the world. The barrier reef
lies 10 to 50km offshore, with several passes between the lagoon and the open-sea.
The whole archipelago is part of a submerged continental mass called Zealandia
which has the shape of a long ridge orientated NE-SW, connecting New Caledonia to
New Zealand. This ridge (Norfolk Ridge), with an average depth of 1000 to 1500m, is
evident from the presence of other small islands such as Belep Island., Ile des Pins or
Norfolk Island. The Loyalty Ridge runs parallel to New Caledonia on the eastern side
and is also evident from a series of small islands. In the vicinity of Grande Terre, the
edge of the reef marks the limit of Zealandia and seafloor dives down to more than
3000m into the New Caledonian and Loyalty Basins (Paris, 1981; Wood et al., 2003;
Keith et al., 2007) (Fig. 1).
1.2. Climate and Ecology
New Caledonia lies astride the Tropic of Capricorn, between 19° and 23°
south latitude. The climate of the islands is tropical, and rainfall is highly seasonal,
brought by trade winds that usually come from the east. Rainfall averages about
1500mm annually on the Loyalty Islands, 2000mm at low elevations on eastern
Grande Terre and 2000 to 4000mm at higher altitude. The western side is drier, lying
in the rain shadow of the central range and an average rainfall averages of 1200mm
per year.
Because of the particular geology of New Caledonia compared to other
oceanic and volcanic islands, the ecology is extraordinary and unique, endemic and
extremely primitive, with plants and animals of Gondwanan origin. Zealandia
separated from Australia 85 million years ago and New Caledonia has been isolated
from any other island for the past 55 millions years (Keith et al., 2007). This
remoteness has allowed conservation of a prehistoric gondwanan biodiversity with no
mammals (except for flying foxes). The main emblematic species of this endemism
are Araucariaceae, Niaoulis (Melaleuca quinquenervia), Kagu (Rhynochetos jubatus)
or Amborella trichopoda (Jaffré et al., 2004; CBNC, 2007; Richer de Forges, 2007).
The main island contains two floral zones: Higher-rainfall areas (eastern side
of Grande Terre and small islands) which support rain forests and a more arid region
with shrinking dry forests caused by extensive European-style farming. In addition to
5
those precipitation zones, soil type, altitude and geographic location have a major
effect on the ecological provinces (CBNC, 2007).
Endemism is not only visible in terrestrial environments but also in the
freshwater ecosystem which has evolved as a result of long isolation. Offshore, the
New Caledonia barrier reef is the world’s second largest coral reef reaching a length
of 1500km. It has developed a great diversity and is home to endangered species such
as dugongs (Dugong dugong), the green sea turtle (Chelonia mydas) and the Nautilus
(Richer de Forges, 2007).
1.3. History, demography and politics
According to Lapita pottery fragment, the first human settlement on New
Caledonia started approximately 3000 years ago. The Lapita culture was replaced in
200BC by the Naia Oundjo period and the domination of the Kanak people (Galipaud,
1992, 1995).
In 1774, James Cook discovered a land which he named New Caledonia
because of its supposed resemblance to Scotland. Several French navigators then
sailed to New Caledonia area, with the first European settlement occurring 1841. In
1853, New Caledonia was proclaimed a French colony, with Nouméa founded in
1854. Initially like Australia, the French republic used New Caledonia as a detention
island. Apartheid-like laws were used against the native people and these lasted until
the end of the Second World War. In the same time, New Caledonia showed rapid and
important economic growth due to nickel mining, becoming the world’s third largest
producer. In the eighties, confrontation between independence fighters and French
partisans degenerated into civil war and ethnic conflict culminating in the Ouvéa Cave
hostage-taking in 1988. This last event caused both groups to negotiate; they signed
the Matignon Accords for a 10-year transitional status with a self-governing
referendum at the end of this period. In 1998, the Nouméa Accord was accepted by
72% of the voters. This allowed a strong autonomy for New Caledonia. The final
referendum about the institutional future of New Caledonia (independency or part of
the French Republic) will be voted on between 2014 and 2018.
The population of New Caledonia is currently 240400 but is growing rapidly
due to the natural birth rate and immigration (ISEE, 2007). The total area covered by
land in New Caledonia is 18575km2 and the population density is 13h/km2. However,
6
in 2004, the population of Nouméa was 146000 inhabitants which represent 2/3 of the
total population. As mentioned before, different ethnic groups are present in New
Caledonia.
- Kanak (Melanesians): 44.1%, which are the native people of New Caledonia.
- Caldoches (Europeans): 34.1%, often mixed blood, offspring of the first Europeans.
- Wallisians & Futunians (Polynesians): 9% who arrived in New Caledonia during
the 60’s and 70’s.
- Tahitians (Polynesians): 2.6%
- French, Indonesian, Vietnamese, Japanese, Chinese, Kabyles, Ni-Vanuatu (10%)
The official language is French; however, there are more than 28
Austronesians local languages and additional languages spoken by immigrants (ISEE,
2007).
1.4. Economy
The New Caledonian gross domestic product (GDP) is estimated to be 3.158
billion US dollars in 2003 which is approximately US$14800 GDP per habitant
(ISEE, 2007). This economy is supported by three main pillars: the nickel industry,
tourism and financial transfers from continental France.
The nickel mining industry represents more than 10% of the GDP and has
increased considerably since 1998, which was the low point (3% of GDP) for the
nickel mining industry in New Caledonia in the last 50 years (Fig. 2). Nickel products
represent 90% of the value of exports from New Caledonia (ISEE, 2007).
19651970
19751980
19851990
19952000
20040.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
% o
f min
ing
in th
e G
DP
19651970
19751980
19851990
19952000
20040.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
% o
f min
ing
in th
e G
DP
Fig. 2. Importance of mining industry in New Caledonia economy (modified from ISEE, 2007).
7
New Caledonia is self-sufficient in livestock but crops are scanty due to
unsuitable soils for farming. The main products are fruits, tropical roots and potatoes.
Most other foods have to be imported. Fishing is mainly based on various species of
tuna and holothurians which are partly exported to Asia. Recently, shrimp aquaculture
has started and is likely to increase in importance (ISEE, 2007).
Tourism represents 4% of the GDP and employs 6% of the total working
population. Tourists mainly comes from Japan (31%), France (28%), Australia (16%)
and New Zealand (6%) (ISEE, 2007).
Finally, large scale financial transfers with continental France are the source of
substantial income, making up 25% of the GDP in 1998 (ISEE, 2007).
The balance of payments is still in deficit, with the value of exports of nickel
ore and ferronickel more than counterbalanced by imports of consumer goods, food
and transport. The recent expansion of in the nickel industry will have lot of
importance to the balance of exports and imports in the future.
8
2.0. Geology
2.1. Regional Geological Settings
New Caledonia is an unusual oceanic island for the southern Pacific. Most
islands of the Pacific are relatively young and formed by recent volcanic activity;
Grande Terre in contrast has a complex Palaeozoic and Mesozoic geology (Fig. 4).
The island is an emerged part of the Norfolk Ridge. This latter structure is,
with the Lord Howe Rise and the Fairway Ridge, part of a large continental plate
called Zealandia which drifted away from the Australian continent as a result of the
Late Cretaceous Gondwana break-up (Dubois et al., 1976; Crawford et al., 2003;
Lafoy et al., 2005). Norfolk Ridge has been studied through the Deep Sea Drilling
Program and through seismic studies. These have revealed a 32km thick sialic crust
(Dubois, 1969) covered by Oligocene to Recent sedimentary rocks (Dupont et al.,
1975; Dubois et al., 1976; Daniel et al., 1976).
The New Caledonia geological history can be divided into three parts which
represents major changes in the geodynamical status of Grande Terre. During the
Palaeozoic and most of the Mesozoic, New Caledonia was attached to the eastern
coast of Australia, somewhere near Brisbane (Glympie Terrane; Cluzel & Meffre,
2002). The primary basement of Grande Terre was covered by several accreting
terranes making a complex mosaic of volcanic, sedimentary and metamorphic units
(Aitchison et al., 1992). This tectonic collage occurred from the Late Jurassic to Early
Cretaceous and is related to the New Zealand Rangitata orogeny (Bradshaw, 1979;
Paris, 1981). These Pre-Rangitata terranes form the central part of Grande Terre and
are often regarded as the basement of New Caledonia.
At the end of the Cretaceous, the Tasman Sea started to open and the various
ridges forming Zealandia also drifted apart forming narrow basins (Davies & Smith,
1971). The New Caledonia basin lies on the west side of Grande Terre. It is a 3000m
deep basin, filled with 200-300m to 4000m of sediments where the thickness is a
function of the proximity to faults which bound the basin (Dubois et al., 1974; Launay
et al., 1979). These sediments are dated as Palaeocene to Recent (Goslin et al., 1972.).
The Loyalty ridge is interpreted to be an Eocene island arc with a back-arc
basin (Cluzel et al., 1999, 2001). The Loyalty basin, a remnant of the fore-arc basin
9
formed during subduction, lies between the Norfolk and Loyalty ridges. It is 2000m
deep and covered by major Oligocene to Recent terrigenous deposits, covering
important extension faults on the edge of the basin (Weissel & Watts, 1975). The
Mohorovičić discontinuity of this area occurs at 17km under the basin and 24km
under the volcanic arc (Collot & Misègue, 1977a,b; Weissel et al., 1977).
At the end of the Eocene, a part of the Loyalty basin was obducted on to
Grande Terre. This supra-subduction event is characterized by different metamorphic
rocks with high-pressure facies or ophiolitic features. These latter ophiolites extend
discontinuously from Papua New Guinea to the South Island of New Zealand. This is
a widespread but diachronic phenomenon which occurred on the Australian plate
margin in the south western pacific during Cenozoic (Aitchison et al., 1995; Auboin
et al., 1977).
Since at least the middle Miocene, the whole Zealandia continent has been
carried along by the Australian plate; its eastern margin is being subducted beneath
the Pacific plate along the Vanuatu trench (Auzende et al., 1995).
2.2. General tectonics
With the exception of the main transcurrent zone, there is no major tectonic
feature in New Caledonia. However, most of the terranes have faulted boundaries and
faults related to different events that are still visible throughout these units.
Thrust faulting is mainly associated with the two obducted terranes of the
Poya and Ultramafic nappes (Fig. 3). These faults are easily visible by their low
dipping angle and the intense serpentinization and mylonitization at the contact
between these terranes and the basement. Serpentinization is also widespread
throughout these terranes on the margins of dip-slip faults.
On the western side of the South Massif, a dextral transcurrent fault is
described by Brothers (1974). This faulting offsets the western margin of the
obducted mafic sheet, spreading ophiolites massifs along the western coast.
The present day New Caledonia is mainly affected by extension faulting with
a NW-NNW trending direction. This faulting has been occurring since early Miocene
as recorded by fluvial Neogene formations (Lagabrielle et al., 2005; Chardon &
Chevillotte, 2006). These recent tectonic movements are responsible for drowned
valleys in the western lagoon and the occurrence of uplifted reefs on the east coast
10
(Lagabrielle et al., 2005). These extension processes seems to be controlled by post-
obduction isostatic readjustments and more recently by the possible flexure of the
oceanic lithosphere currently subducting under the Vanuatu trench at a rate of
12cm/yr (Lagabrielle et al., 2005).
Strike-slip faults
Extension faultsOverthrust faultsLimits of the New Caledonia lagoon
0 50 100
N
New Caledonia Basin
Loyalty Basin
Strike-slip faults
Extension faultsOverthrust faultsLimits of the New Caledonia lagoon
0 50 1000 50 100
NN
New Caledonia Basin
Loyalty Basin
Fig. 3. Simplified tectonic map of New Caledonia (modified from Chardon & Chevillotte, 2006).
2.3. Terranes of New Caledonia
Four geological groups can be distinguished in New Caledonia and represent
the main phases of the island geological history.
- Ante-Senonian terranes [Koh, Téremba, Central Chain, Boghen]
- High-Pressure metamorphic terranes [Koumac, Diahot, Pouébo]
- Obducted terranes [Poya, Ultramafic nappe]
- Post-obduction rocks of intrusive and sedimentary origins.
11
Fig. 4. Simplified geological map of New Caledonia (modified from BRGM & DIMENC, 2005).
2.3.1. Ante-Senonian terranes
Koh Ophiolite
Age : Late Carboniferous to Permian
Lithology : Gabbro, dolerite, boninite, tholeiite, plagiogranite,
chert, sandstone, siltstone
Thickness : 3000m at Koh, thinner in the northern and southern units
Context : Convergent margin settings; Supra-subduction from a back-arc basin
References : Guérangé et al., 1975; Paris, 1981; Cameron, 1989; Meffre et al.,
1996; Aitchison et al., 1998; Ali & Aitchison, 2002
The Koh terrane is a part of the Central Chain volcanics. It occurs in several
small units in the middle of Grande Terre and is considered to form the oldest rocks in
New Caledonia. In the type locality of Koh, where the ophiolite is the thickest, three
main units are described (Meffre et al., 1996) (Fig. 5).
12
- Upper tholeiite basalts and intrusions : This upper unit is 100 to 300m thick
and is the least altered rock of the Koh terrane. Intrusive rocks are common
with small dikes and or small bodies of altered gabbros and diorite.
- Boninite pillows and felsic volcanics : This member is restricted to the Koh
area and separates the lower from the upper tholeiites. It is made of long
pillow lava tubes associated with cherts, hyaloclasites and breccias in a 250m
thick sequence. The lithology changes upwards to more dacitic compositions
with prominent quartz, clinopyroxene and tuffs.
- Cumulate rocks and lower tholeiite : This is the lowermost part of the Koh
ophiolite. Plutonic rocks forming the base of this unit are cumulate gabbros
with minor gabbronorite and pyroxenite. These lithologies evolve
progressively upwards into isotropic gabbros cut by dikes of plagiogranite and
dolerite which feed tholeiitic pillow-lavas. On the basis of geochemical
pattern, all these rocks form one magmatic sequence. Peridotites and
ultramafics cumulates, common at the base of many ophiolites, are absent in
Koh, probably removed during obduction or subsequent strike-slip faulting.
Fig. 5 : Stratigraphical column of the Central Chain terrane and Koh ophiolites. Diagonal lines are faults and arrows show that Central Chain sedimentary sequence continues conformably upward (modified from Meffre et al., 1996).
Subseafloor alteration is widespread in the basaltic lavas and characterized by a
greenschist facies with numerous secondary paragenese (chlorite, actinolite,
pumpellyite, prehnite, serpentine) affecting petrological observations. Moreover,
13
northern ophiolites (Cantaloupai, Sphinx & Tarouimba) are affected by blueschist
metamorphism (Ali & Aitchison, 2002).
Lateral variations are mainly noticeable by the absence of boninitic units in other
ophiolites outcrops. Although the sequence remains fairly thick in Sphinx and
Tarouimba, in other units, only the shallower magmatic rocks are preserved (Fig. 5).
On the basis of plagiogranite zircons, U-Pb dating gives an age from 302±7 to
290±5Ma for the formation of the ophiolites (Aitchison et al., 1998). These ages are
similar to Dun Mountain Ophiolite Belt in New Zealand and geochemical similarities
are also to be found with that terrane. The occurrence of N-MORB tholeiite at this
time has some importance to geodynamic reconstruction of the eastern margins of
Gondwana during Late Palaeozoic and early Mesozoic.
Central Chain Terrane
Age : Permian to Upper Jurassic
Lithology : Volcanoclastic sandstone; tuffaceous and black
siltstone; conglomerate
Thickness : >7000m
Context : Convergent margin settings; SSZ from a back-arc basin Resources : Au
References : Guérangé et al., 1975; Maurizot et al., 1985; Meffre et al., 1996; Potel
et al., 2006; Potel, 2007
The Central Chain Terrane is in a continuity of mafic ophiolites of the Koh
terrane. It crops out in the mountains and on the east coast, covering approximately
15% of the island (Guérangé et al., 1975).
This terrane is relatively monotonous, starting with the pelagic green and red
chert overlying pillow basalts of Koh Terrane in a sequence 130m thick. This unit is
succeeded by tuffaceous siltstones, volcanoclastic sandstones and conglomerates for
approximately 1150m. Volcanoclastics are then interbedded with black siltstones
which provide a paleontological dating based on ammonoid fauna of mid-Triassic
(H.J. Campbell, IGNS, New Zealand, written communication, 1990)
contemporaneous with the New Zealand Maitai terrane. Black siltstones
approximately 1000m thick are overlain by other volcanoclastic sandstones and
14
conglomerates which continue up section and form a Middle Triassic to Upper
Jurassic sedimentary sequence a few thousands meters thick.
North of the Cantaloupai Koh Ophiolite, rocks are affected by the same
metamorphic event that affected the Diahot and Pouébo Terrane. TA lawsonite-facies
in the volcanoclastic sequence is apparent as well as some fine grained blue
amphiboles. The lowest metamorphic grade is reached west of Ponérihouen where
stilpnomelane-chlorite metapelites were investigated by Potel et al. (2006) and Potel
(2007). The latter also shows an increasing metamorphism towards the southwest,
reaching glaucophane isograde close to the contact with the Poya Terrane (Cluzel &
Meffre, 2002; Potel, 2007).
Téremba-Moindou Terrane
Age : Mid-Permian to Late Jurassic
Lithology : Calc-alkaline volcanoclastic sedimentary rocks
Context : Convergent margin settings; Proximal arc-related terrane
References : Paris, 1981; Campbell, 1984; Campbell et al., 1985;
Aitchison et al., 1998
The Téremba block is the smallest unit of the ante-Senonian terranes. It occurs
only on the south-western coast of New Caledonia where it is largely covered by
Quaternary alluvium.
The base of the terrane is composed of calc-alkaline volcanic rocks, which
become more terrigenous with calc-alkaline volcanoclastic lithology in the upper
section. The eastern part of the terrane is dominated by shallow to deep volcanoclastic
sedimentary rocks; volcanic rocks are absent. Further east, a poorly understood fine-
grained volcanoclastic sedimentary rock is sometimes described as the Moindou
Terrane (Aitchison et al., 1998).
The terrane was affected by a low-grade high-pressure metamorphic event
which brought the Téremba province in the pumpellyite-chlorite range (Paris, 1981;
Campbell et al., 1985; Cluzel & Meffre, 2002).
Many comparisons have been made between the Téremba terrane and the
Murihuku Group in New Zealand. Similarities includes the fauna (Campbell & Grant-
Mackie, 1984 ; Ballance & Campbell, 1993), palynomorphs (de Jersey & Grant-
15
Mackie, 1989), volcanoclastic sources (Roser & Korschand, 1988) and age (Campbell
& Grant-Mackie, 1984; Aitchison et al., 1998).
Fig. 6. Reconstruction of Eastern Gondwana margin during Jurassic. Ante-Senonian terranes are represented in their more likely geodynamical position (modified from Cluzel & Meffre, 2002).
Boghen Terrane
Age : Lias and older
Lithology : Schist, metagreywacke
Thickness : Several thousands of meters
Context : Derived volcanic-arc rocks
References : Avias & Gonord, 1973; Paris, 1981; Campbell et al., 1985;
Cluzel, 1996; Cluzel & Meffre, 2002
This terrane is formed by three main massifs (Boghen, Ouango, Netchaot) and
many smaller tectonic units (Karaka, Dothio,…). All boundaries are faulted and no
stratigraphic correlations are possible.
The base is formed of 500m of alternating tholeiitic pillow lavas, hyaloclasites
and radiolarites. A few breccia horizons and sparitic limestone are also present. The
upper part of the terrane consists of a thick monotonous schist and greywacke
sequence. The schist composition varies between pelitic, carbonaceous and mafic
volcanic ‘greenschist-blueschist’ end-members. Psammitic layers contain
volcanogenic plagioclase and clasts of angular quartz and pelagic chert. These
sediments are interpreted as having been deposited within a deep sea fan and derived
from mixed terrigenous and volcanic-arc sources. These sediments were probably
16
accumulated on the oceanic crust and were subsequently reworked in an accretionary
complex.
Boghen terrane seems related to Torlesse rocks in New Zealand, sharing same
zircons age. The Torlesse Group is more proximal than Boghen but both show detrital
Precambrian zircons from Gondwana. However, their histories diverge during the
Jurassic when the Boghen terrane is partially subducted to 20-25km depth into a
blueschist facies (Fig. 6) and then exhumed through the Central Chain terrane during
late Mesozoic (Cluzel & Meffre, 2002).
2.3.2. High pressure rocks
Formation à Charbons
Age : Cenomanian to Santonian (Upper Cretaceous)
Lithology : Coal, conglomerate, arkose, sandstone, siltstone
Thickness : 200 to 1000m
Context : Transgressive sedimentary sequence
References : Aronson & Tilton, 1971; Aitchison et al., 1995; Aitchison et al.,
1998; Cluzel et al., 1999.
The “formation à charbons” unit (translation: coal-bearing formation) is the
first formation to overlay the eroded Rangitata basement and is regarded as the clear
limit to the end of the Carboniferous to Lower Cretaceous accretion process.
The formation is characterized by deltaic deposits from the Australian
continent which alternate some mangrove facies, rare limestone and coarse sandstone
and volcanics (Black, 1995; Picard, 1995) (Fig. 7). In the Koh area, sedimentation
starts above the basal unconformity with 20 to 30 meters of sandy matrix-supported
conglomerate where pebble-sized clasts are formed of rocks largely derived from the
pre-Cretaceous basement. This conglomerate evolves in quartz-rich sandstone with a
thickness of 50 to 180m (Aitchison et al., 1998). Clastic sedimentation is less and less
pronounced and the upper part is dominated by organic-rich layers of siltite and
argillite (Cluzel et al., 1999). Large variations of thickness and the presence of
marginal outcrops with breccias and olistostromes features underline the existence of
active faults and a tilted block system.
17
Zircon dating has been done out on Senonian arkosic sandstone layers of the
formation à charbons. Ages show two main populations of 90-140 Ma and 170-220
Ma as well as some rare detrital Precambrian zircons from 670±30 to 1055±40 Ma.
Jurassic zircons are similar to those found in Torlesse rocks and could be related to an
Australian (New England) orogen source but this remains problematic (Aitchison et
al., 1998; Aronson & Tilton, 1971).
Fig. 8. Pre-obduction megasequence of Bourail flysch during Late Eocene with upward coarsening and olistotrome. (modified from Cluzel et al., 2001).
Fig. 7. Post-Jurassic sedimentary sequence in Nouméa area with terrigeneous, volcanoclastics and hemipelagic rocks (modified from Cluzel et al., 2001).
Koumac Terrane
Age : Upper Cretaceous to basal Eocene
Lithology : Chert, limestone, marl, flysch
Thickness : >200m
Context : Transgressive deep (meta-)sedimentary sequence
References : Cluzel et al., 1999; Potel et al., 2006
This unit is concordant with the upper part of the Formation à Charbon. It
occurs throughout New Caledonia but is especially abundant in the north western part
of the island where most of the terrane shows a low-grade high pressure – low
temperature metamorphism.
18
The lower part of this formation starts with sandstones which show an
increasing content of carbonate along with stratigraphy. Planktonic foraminifers-
bearing marls are the main basal lithology, overlain by 100-170m of fine-grained
black chert (phtanites) containing diverse siliceous organisms of Campanian to Late
Paleocene age (Bodorkos 1994; Paul, 1994). In many areas, this black chert is
interbedded with pelagic micrite which is sometimes the dominating lithology (Fig.
8). However the trend of this terrane is to be more siliceous in the upper part, with age
ranging up to middle Eocene (Gonord, 1977; Maurizot & Feigner, 1986). In the north-
western area, Koumac terrane boundaries are not well defined to the east. Using the
lawsonite metamorphic isograde as the boundary between Koumac and Diahot
terrane, Potel et al. (2006) placed the limit of the Koumac terrane on the edge of
Bwaluyu Fault.
The evolution from the Formation à Charbons to these cherts and micrites is
clearly seen as a progressive decrease of terrigenous material. This observation is
related to the opening of New Caledonian basin and the separation between Lord
Howe Rise and Norfolk Ridge (Cluzel et al., 1994). The increasing siliceous content
in those rocks represents gradual deepening marine conditions related to post-rift
thermal cooling and associated subsidence (Aitchison et al., 1995).
Metamorphism in the Koumac Terrane is discreet as is the case when it occurs
in siliceous rocks. However, a prehnite-pumpellyite facies is described in basic
igneous rocks (Brothers, 1974; Black 1977). Clay minerals provide more information
on the basis of their Kübler and Árkai index and vitrinite reflectivity is of some help
in this low-grade metamorphism (Potel et al., 2006).
Diahot Terrane
Age : Upper Cretaceous to Middle Eocene
Lithology : Blueschists
Context : subducted sedimentary and volcanic rocks
Resources : Cu, Pb, Zn, Ag, Au, Bi, Sn
References : Black & Brothers, 1977; Clarke et al., 1997; Fitzherbert et al., 2003
19
The Diahot terrane is a metamorphic unit in the northern part of New
Caledonia. It lies between the Koumac and Pouébo terranes as the middle part of the
HP-LT metamorphic belt.
The Diahot terrane ranges from lawsonite to epidote—omphacite facies and/or
ferro-glaucophane—lawsonite to albite—epidote—omphacite zone (Black &
Brothers, 1977) (Fig. 9). Rocks forming this terrane are similar to the Koumac unit,
with meta-sedimentary and meta-volcanic rocks. This heterogeneity leads to several
different metamorphic zones (Clarke et al., 1997; Fitzherbert et al., 2003).
- Basaltic protolith
- Zone 1 : Lawsonite blueschist (Lawsonite-Omphacite-Glaucophane)
Fine-grained metabasalts which retained their igneous textures and
remains of the basaltic mineralogy (augite, plagioclase).
- Zone 2 : Epidote blueschist (Lawsonite-Clinozoisite-Garnet)
The metabasites are coarse-grained and two lithological subfacies are
distinguished with a spessartine-bearing assemblage which sometimes sees
the disappearance of lawsonite and the formation of almandine in coarser
areas.
- Zone 3 : Epidote-Hornblende blueschist (Clinozoisite-Almandine-Hornblende)
Even if the protolith seems slightly different, this zone is still referred
as a metabasite. Barroisitic hornblende defines the zone and makes, along
with almandine and clinozoisite, the main component of these rocks.
- Zone 4 : Hornblende-paragonite eclogite (Clinozoisite-Almandine-Omphacite)
This zone is the highest grade in Diahot terrane and is referred as
eclogite type-II in Clarke et al. (1997). It is characterized by the
reappearance of omphacite-forming layers between hornblende-
clinozoisite rich zones.
- Metasedimentary rocks
- Ferro-glaucophane-Lawsonite
In the southwest part of Pam peninsula, Fe-glaucophane-albite
phengite fine-grained meta-sedimentary rocks are described (Yokohama
et al., 1986) and sometimes contain some lawsonite, chlorite and titanite.
- Glaucophane-Albite-Garnet schist
These schists, who occur in the central part of Pam peninsula, are
carbonaceous and fine-grained.
20
- Albite-Epidote-Omphacite
Because of the large variety of metasedimentary protoliths, several
assemblages occur in that zone, containing phengite, garnet, glaucophane,
chloritoid
- Felsic eclogites
- Felsic eclogites were described by Black et al. (1988) in the vicinity of the
peak Bouehndep and mapped as meta-rhyolite by Maurizot et al. (1989). These rocks
are feldspar-rich variations of Albite-Epidote-Omphacite facies. Jadeite, phengite,
chloritoid and chlorite are also present.
According to metabasites assemblage, Pressure-Temperature conditions range
from 350°C/8-10kbar for zone 1 to 620°C/17kbar in zone 4.
Pouébo Terrane
Age : Upper Cretaceous to Middle Eocene
Lithology : Eclogite
Context : subducted volcanic rocks
References : Clarke et al., 1997; Carson et al., 1999, 2000;
Spandler et al., 2005
The Pouébo rocks are a high-pressure metamorphic terrane which lies along
the northernmost eastern coast of New Caledonia. It stands as the continuity of Diahot
terrane through higher metamorphic conditions.
The Pouébo terrane is a well known area of New Caledonia showing eclogite-
facies for metabasic and metasedimentary rocks. These eclogites occur in a
glaucophanite matrix made by rehydration of eclogite (Maurizot et al., 1989) (Fig. 9).
- Eclogite Type I
This metamorphic rock forms the main part of the Pouébo terrane
even if most of the time, rehydration modified the mineralogy to garnet
glaucophanite. Eclogite contains large grains of garnet enveloped in a
granoblastic foliation of barroisitic hornblende, quartz, epidote, phengite
and rutile, with or without omphacite, apatite and titanite.
- Eclogite Type II
21
Also described as the Hornblende-Paragonite eclogite (Zone 4) in
Diahot terrane (Fitzherbert et al., 2003).
- Eclogite Type III
This type is inferred as metamorphosed chert, occurring in rare
meta-quartzite lens of the metabasic eclogite. Quartz is dominant (>70%)
with andradite, epidote, glaucophane and titanite.
- Garnet Glaucophanite
Garnet glaucophanite represents the hydrated and variably
recrystallized equivalent of metabasite eclogite type I. These rocks are
almost everywhere dominated by crossite and clinozoisite with garnet.
Different sub-types are distinguished according to their content in
barroisitic hornblende, omphacite and phengite (Carson et al., 2000).
- Shear Zone
Discrete shear zones of 1 to 100m wide cut type I eclogites. They
are not related to shallow exhumation shear zones or to the distribution of
metamorphic grade in the Pouébo terrane. These shear zones are
characterized by a greenschist facies assemblage of crossite, chlorite,
clinozoisite, barroisite, actinolite and phengite. Garnet is partially
pseudomorphed by albite and chlorite (Clarke et al., 1997; Carson et al.,
2000).
Based on relic mineral assemblage, the highest metamorphic conditions
reached by Pouébo eclogite are 24kbar at 600°C. Hydration of Pouébo eclogite in
glaucophanite occurs during decompression at P=14kbar. The peak eclogitic
metamorphism took place 44Ma ago (Spandler et al., 2005) and the unroofing and
cooling of the terrane lasted until 34Ma (Cluzel et al., 2001).
22
N
0 50 100Lawsonite in
Na-amphibole inEpidote inGarnet inHornblende inOmphacite in
NN
0 50 1000 50 100Lawsonite in
Na-amphibole inEpidote inGarnet inHornblende inOmphacite in
Fig. 9. Simplified geological map of metamorphic isograd in Northern New Caledonia. (modified from Black & Brothers, 1977; Spandler et al., 2003).
2.3.3. Obduction nappes
Poya Terrane
Age : Senonian (Upper Cretaceous) to Paleogene
Lithology : Basalts, hyaloclasites, diverse sediments
Thickness : <2000m
Context : obducted marginal basin oceanic crust
Resources : Mn, Co, Cu, Au
References : Eissen et al., 1998; Ali & Aitchison, 2000; Cluzel et al., 2001
Poya terrane is a regionally extensive unit of New Caledonia which occurs
mainly on the western coast between Bourail to Koumac and in several smaller
outcrops on the east coast and Nouméa area.
Called “Formation des Basaltes” (Translation : Basalts Formation) by previous
authors (Routhier, 1953), the Poya terrane is the upper section of an oceanic crust.
Therefore, it is mainly composed of pillow basalts which alternate with bathyal black,
red or green argillite and chert. Some massive basalts occur as well along with rare
outcrops of dolerite and fine-grained gabbro. Magmatic rocks are also associated with
minor oceanic floor mineralization.
The MORB geochemical signature of the Poya tholeiite clearly shows it to be
allochtonous feature and the Poya terrane is now confirmed as an obducted oceanic
crust. Radiolarian fauna found in the chert shows Campanian to basal Eocene ages.
The nearly complete absence of continental sediments would indicate that the Poya
terrane was formed in an intra-oceanic environment (Cluzel et al., 2001).
The Poya terrane has been affected to various degrees by low-temperature and
low-pressure metamorphism. The resultant paragenese are greenschist facies or lower
grade. Another metamorphic event occurred during the Eocene and is evident from
now by the presence of infra-subduction blueschist facies (crossite-glaucophane) in
the northeast outcrops of the Poya basalts.
Numerous dykes cross the Poya terrane but all of them are younger than the
terrane itself, crossing also the ultramafic nappe. Ca-rich boninite dykes have been
studied and revealed to be of a Miocene age and not directly related to the subduction
events (Black et al., 1994; Eissen et al., 1998). However in some places (Pinjen and
23
Foué peninsula), older alkaline basalts have been found and are interpreted as
remnants of an oceanic island formed on the Poya oceanic floor (Fig. 10).
Due to complex folding, faulting and disruption, the Poya terrane seems to be
emplaced as a duplex of tectonic slices pinched beneath the ultramafic terrane. The
asymmetric folding observed was probably formed during or immediately after
eclogite exhumation.
Fig. 10. A geodynamic model for the evolution of the Eocene accretion/subduction complex of New Caledonia (modified from Cluzel et al., 2001).
24
Ultramafic Terrane
Age : Upper Cretaceous
Lithology : Peridotite, Gabbro, Chromitite, Felsic rocks
Thickness : <4000m
Context : obducted oceanic crust and mantle
Resources : Ni, Co, Cr, Fe, Au, PGE
References : Prinzhofer, 1980; Dupuy et al., 1981a; Paris, 1981
The ultramafic nappe is the main feature of New Caledonia geology. It covers
8000km2 of Grande Terre but is thought to have once overlain the whole island
(Dupuy et al., 1981a)(Fig. 10). The main outcrops include several massifs on the west
coast, some small nappes in the central chain area and the ‘Grand Massif du Sud”
which dominates the whole southern part of the island. Peridotites also occur on
islands of the Norfolk Ridge in altered outcrops (Belep Is., Pine Is., Ouen Is.).
Most of the ophiolitic massifs have similar properties. The main exception is
the Tiébaghi massif which shows some lherzolite outcrops and important chromitite
bodies. The large Southern massif is also much more diverse than other nappes and
show upper terms of the ultramafic series whereas other massifs are only part of the
depleted mantle. However, only 20% of the southern massif is above the paleo-Moho
(Dupuy et al., 1981a) and the absence of upper and middle oceanic crust is probably
due to deep erosion or tectonic detachment (Cluzel et al., 2001)(Fig. 11). In addition
to this, most of the rocks from the ultramafic terrane are deeply serpentinized and
lateritization affect important surface of the nappe, making fresh outcrops relatively
rare compared to the extension of this terrane.
From bottom to top, the ultramafic sequence in the southern massif is mainly
divided in harzburgitic mantle, dunitic transition zone and gabbroic crustal rocks (Fig.
11). This ultramafic nappe lies on Poya basalts and occasionally on the Central Chain
terrane. Rare high-Ca boninites are also described as sandwiched within a fault zone
between Poya and the ultramafic nappe. These last rocks remain enigmatic and might
represent manifestations of near-trench fore-arc volcanism (Aitchison et al., 1995).
25
Fig. 11. Simplified geological map of the southern part of the Grand Massif du Sud (inspired from Noesmoen, 1971; Guillon et al., 1974; Guillon & Trescases, 1976; Trescases & Guillon, 1977).
The lower part is magnesian harzburgite (Mg# = 0.93) composed of forsterite
and enstatite and minor chromian spinel. Sulphides and alloys (pentlandite,
heazlewoodite, awaruite, copper) are also present in this lower zone, associated with
orthopyroxene rich layers. The main variations in the harzburgite zone are a decrease
of the Mg-number from 0.93 at the base to 0.90 in the transition zone, a decrease of
nickel content in silicates and an increase of MgO, Al2O3 and TiO2 in spinel phase
along with stratigraphy. Foliation is clearly visible, underlined by porphyroblastic
orthopyroxene and layering is sometimes well developed with centimetric segregated
olivine and orthopyroxene layers (Guillon et al., 1974; Guillon & Trescases, 1976;
Trescases & Guillon, 1977).
The dunite zone is discordant with regard to the harzburgite. The contact is
progressive over a few tens of meters with the disappearance of orthopyroxene. These
dunitic bodies have complex relationship with harzburgite with many cross-cutting
apophyses. The main minerals are forsterite and chromian spinel and rare plagioclase
(melatroctolite) in dunite bodies of Prony area.
26
The transition zone between dunite and gabbro is gradual and shows the
successive appearance of orthopyroxene, calcic plagioclase (An75-90) and
clinopyroxene in the cumulative dunite. This leads to the formation of numerous rock
types such as orthopyroxene-dunite and harzburgite, troctolite, wehrlite and noritic
and anorthositic rocks. These rocks are emplaced with a cumulative structure and are
reminiscent of stratiform complexes. This fractionated crystallization which leads to
the formation of the oceanic basaltic crust, has a strong geochemical evolution with a
decrease of iron, magnesium and nickel and enrichment in aluminium, calcium and
titanium (Guillon & Trescases, 1976).
Gabbros crop out at the top of the sequence, just above the dunite and
transition zone. Mineralogy is mainly calcic plagioclase, chromian diopside, pigeonite
and hypersthene but alteration is frequent and ouralitisation and saussuritisation form
tremolite, nephrite, epidote, smaragdite, etc. Layering is still visible, mainly as
alternation of pyroxenitic and anorthositic decimetric layers. The general composition
is gabbronoritic.
Fig. 12. Stratigraphic log of the ultramafic nappe of Southern New Caledonia. The thickness of harzburgite has been reduced.
Many dikes occur through the ultramafic terrane. These are related to different
processes and show different compositions and geochemical affinities.
Dunite dykes and pods can be concordant or discordant. Their formation is
related to the isothermal and peritectical reaction which leads to the consumption of
27
orthopyroxene out of harzburgite and forms dunite channels (Kelemen, 1990). This
reaction also helps in the precipitation of chromite and chromitite bodies in small
magmatic chambers.
Concordant pyroxenitic dykes are related to segregation processes in
harzburgite giving alternation between dunite and orthopyroxenite. Discordant dikes
are related to a silica enrichment of the mantle rocks in confined zone. Some of these
dikes could be related to a pre-obduction subduction process and show a modal
composition of orthopyroxene, clinopyroxene and amphiboles.
Tholeiitic basaltic dikes occur in the peridotite of the gabbro. These feeding
dikes have an intermediate olivine fractionation which contrasts with the gabbro itself
which show limited fractionation. The theoretical source of these dykes is the anatexis
of pyrolite (strongly depleted mantle) to partial melting ratio of 11 to 13% (Dupuy et
al., 1981a).
In the higher part of the mantle section, felsic dykes and small intrusions are
present with composition ranging from diorite to granite. Geochemical features, age
and field relationship do not fit with plagiogranites described in other ophiolites.
However, by comparison to the post-obduction granitoids, these rocks do not show a
strong contact metamorphism with the ultramafic rocks. Their age based on zircons is
around 50Ma (Prinzhofer et al., 1980; Cluzel et al., 2006).
The whole ultramafic sequence is 4000m thick (Harzburgite: 3000m; Dunite:
500m; Transition zone: ±100m; Gabbro : >300m) and is still attached in places, to the
Loyalty basin seafloor (Paris, 1981; Prinzhofer, 1981). By comparison with other
ophiolites and oceanic crust, it seems that 8km of rocks are missing over the gabbros
(Prinzhofer et al., 1980), removed by tectonic processes or erosion. High temperature
stretching lineation and wrench shear zones visible in peridotites are interpreted as
transform faults (Prinzhofer et al., 1980) and provide evidence that the obduction
which occurred in the Eocene was a north over south overthrusting direction as a
result of the synchronous opening of the Loyalty basin (Collot et al., 1987).
The age of the ultramafic and events which affected these rocks are difficult to
determine. On the basis of K-Ar geochronology, crosscutting dikes displays two age
groups of 77-100Ma and 48Ma (Prinzhofer, 1981). This would mean that the oceanic
crust was probably formed at the beginning of the Late Cretaceous and the 50Ma
event, which is also dated on zircon (Aitchison et al., 1995; Cluzel et al., 2006), is
28
probably related to a pre-obduction subduction process which has also formed the
blueschists and eclogite terranes of Diahot and Pouébo.
2.3.4. Post obduction rocks
Post-obduction granitoids
Age : Late Oligocene
Lithology : Granodiorite, adamellite
Context : subduction related magmatism and slab break-off
Resources : W, Mo, Au, Sb
References : Cluzel et al., 2005
These intrusive rocks are observed in two areas, Koum-Borindi on the east
coast, just south of Thio and St Louis area near Nouméa. Host rocks are peridotites
from the ultramafic terrane.
The St Louis intrusion is a relatively homogeneous hornblende-biotite
granodiorite with numerous subvolcanic dykes and comagmatic enclaves. The typical
composition is plagioclase (40-50%), K-feldspar, quartz, biotite and hornblende with
pyroxene relics. Accessories are apatite, zircon, rutile, magnetite and ilmenite which
crystallized early and epidote, muscovite and chlorite formed during postmagmatic
alteration. Dikes are mainly microgranodiorite intruded in the hot host rock whereas
enclaves are darker hornblende-rich fine-grained rocks (Cluzel et al., 2005). The St
Louis stage which resulted from the obduction event (32Ma) related to this intrusion
(27Ma), is interpreted as the result of the new subduction zone forming along the west
coast in response of the opening of the North Loyalty basin (Cluzel et al., 1999, 2002;
Paquette & Cluzel, 2007 ).
The Koum-Borindi intrusive complex is more heterogeneous and
differentiated. Two main facies are present: a leucocratic tonalite (plagioclase, K-
feldspar, quartz and biotite) mainly found in dykes and intrusive stocks and an
amphibole-biotite-bearing granodiorite apparently restricted to the main Koum
massif. The tonalite facies varies in quartz (15-40%), plagioclase and K-feldspar
where plagioclase is zoned and K-feldspar show perthite and/or granophyre
subsolidus textures. In the granodiorite, amphibole frequently displays Mg-rich biotite
(Mg#=0.59) pseudomorphs. Corroded quartz grains also occur in the subvolcanic
29
dykes. These observations of chemical instability are probably created by
intraplutonic magma mixing processes (Cluzel et al., 2005). The Koum-Borindi Stage
(24Ma) is related to the shrinking of the New Caledonia basin, the break-off of the
older slab and the exhumation of the HP/LT terrane complex (Cluzel et al., 2002;
Paquette & Cluzel, 2007 ).
Post-obduction Fluvial and Lacustral Formations
Age : Late Oligocene to Lower Miocene
Lithology : Conglomerate, breccia to sandstone, calcarenite
Context : Fluvial erosion of ultramafic terrane
Resources : Ni, Co, Mn, Au, PGE, Limestone
References : Coudray, 1976; Paris, 1981; Chevillotte, 2005;
Chardon & Chevillotte, 2006
After the obduction of the oceanic crust, erosion affected the ultramafic
terrane and produced some onshore sedimentary deposits which have not received
much attention until recently. Three phases are known and called Goa N’Doro
formation, Népoui formation and unspecified lateritic planations which have formed
up to the present day.
The Goa N’Doro Formation is a Miocene fluvial complex of sandstone
overlain by conglomerate. It occurs mainly as a cover on the ultramafic terrane and on
some parts of the Koumac and Poya terrane on the west coast (Orloff & Gonord,
1968; Orloff, 1968; Carroué, 1972; Guillon & Trescases, 1975; Trescases, 1975;
Paris, 1981; Vogt et al., 1984).
The lower sequence (Goa N’Doro s.s.) comprises conglomerates and breccias
of a reworked bedrock and material derived from weathering profiles. It is then
overlain by microconglomerates and sandstones passing into siltstones with traces of
paleosols, indicative of a flood plain environment. The younger conglomeratic unit
(Goa N’Doro s.l.) is almost exclusively made up of peridotite pebbles, rests on a
channelling erosion surface truncating both the Goa N’Doro s.s. and peridotite
substrate. This formation has a strong lateral variability related to the geomorphic
environment but most of the stepped lateritic surfaces from 1600 to 400m elevation
are recognized as part of these rocks (Chevillotte, 2005; Chardon & Chevillotte,
2006)(Fig. 13).
30
Rocks described as the Népoui Formation (Coudray, 1976) are a deltaic
sequence of Aquitanian to Langhian age showing a gradation from prominent coarse
conglomeratic fluvial deposits to biocalcarenitic deposits (Coudray, 1976; Paris,
1981). Further studies and the description of other post-obduction fluvial deposits
seem to indicate that the upper conglomerate of the Goa N’Doro Fm. is correlated to
the early Miocene Népoui Fm. (Chardon & Chevillotte, 2006).
Fig. 13. Stratigraphical columns of Goa N’Doro and Népoui formations with correlation lines. Elevation thicknesses are in meters (modified from Chardon & Chevillotte, 2006).
31
The complex assemblage of these sedimentary bodies is mainly due to an
equilibration profile with a fluctuating sea level creating erosional unconformities.
Two regional river aggradation cycles are distinguished, each of which is preceded by
a deep river incision phase. Moreover, Neogene extension tectonics have deeply
affected the deposition of these rocks with the disruption and collapse of the aggraded
sedimentary sequences (Chardon & Chevillotte, 2006).
Quaternary Alluvial and Recifal deposits
Age : Quaternary
Lithology : Sand, Silt, Limestone
Context : Recent deposits
Resources : Limestone
References : Lagabrielle et al., 2005
The Neogene and Quaternary epochs are characterized by the erosion of
Grande Terre and the development of the lagoon. Due to extensional tectonic
movements, fault blocks have moved on both side of the island. In consequence, some
coral reefs have been uplifted on the east coast tilted blocks and drowned valleys and
sediment-filled graben occur beneath the lagoon floor of the west coast (Lagabrielle et
al., 2005).
32
3.0. Mining in New Caledonia
Interest in the mineral deposits of New Caledonia started in 1864 with the
discovery of garnierite (Dana, 1873) by the French geologist and explorer, Jules
Garnier. Industrial mining started in 1876 in New Caledonia and has not stopped
since. At the present time, New Caledonia is the world’s second ranked producer of
ferronickel just after Japan and the fourth ranked source of nickel ore (laterite and
sulphides) after Russia, Canada and Australia (Mining Journal Ltd., 2003; Jorgenson
et al., 2004; Kuck, 2006, 2007) (Fig. 14).
Fig. 14. Main nickel laterite world producer. Saprolite has spots and limonite small lines for a same country (modified from Elias, 2002).
This industry has a major impact on the New Caledonian economy and
politics, accounting for more that 12% of the gross domestic product (GDP),
employing more than 3200 workers and contributing an estimated 90% of foreign
exchange earnings in 2007 (Lyday, 2003, Australian Trade Commission, 2007).
Politically, regarding to the Kanak indigenous community and relationships with
France, the nickel industry has strong interactions and could play a definitive part in
the forthcoming independence referendum.
The mineral industry of New Caledonia is dominated by the mining of
nickeliferous laterite-saprolite-limonite-garnierite and the production of ferronickel
and nickel-cobalt matte of various commercial grades. 7Mt of nickel ore are extracted
each year (4.5Mt of garnierite, 2.6Mt of laterite). 4Mt are exported to Asia and
33
Australia and the remaining 3Mt are processed locally by Société Le Nickel (SLN)
(Australian Trade Commission, 2007)(Fig.15).
Fig. 15. Nickel mineral production of New Caledonia from 1900 to 2004 (ISEE, 2007).
Since 2000, the New Caledonia territory has been is free to make its own
decision concerning hydrocarbon, nickel, cobalt and chromium resources. The three
provinces have their own mining policy (mining, environment, work) and two groups
are working to maintain coherency between institutions and legal procedures (Fig.
16).
Conseil des Mines (CM) : Mining Council is where the French state, New
Caledonia and the provinces try to reach an accord concerning mining issues. Council
members are executive of government and provinces councils.
Comité Consultatif des Mines (CCM) (Consultative Mining Council) has State
representatives, New Caledonian representatives, congress, senate, professional and
syndical organizations and environment protection associations. This group is
consulted for any mining regulations that are proposed by the Congress or the New
Caledonian Assembly.
Service de Géologie et des Mines (Geological Survey) : The main objective of
this institution is to regulate and facilitate the mining activity in a variety of ways.
This service is a subdivision of DIMENC and works in parallel with the French
Geological Survey (BRGM).
34
Direction de l’Industrie, des Mines et de l’Énergie de Nouvelle Calédonie
(DIMENC) has as its objective to control and promote the New Caledonian industry
abroad.
Fig. 16. Application procedure for acceptance of mining issues.
Application InstructionInquiry
DeliberationProject
CCMproposal
CMproposal
Haut-commissaire
Secondreading
New proposition
Accepted Provincialdeliberation
NotificationPublication
Accepted
Not accepted
New CaledonianGovernment
Not accepted End of the procedure
8 days
8 days
Eventual procedure
2 months
Application InstructionInquiry
DeliberationProject
CCMproposal
CMproposal
Haut-commissaire
Haut-commissaire
SecondreadingSecondreading
New proposition
AcceptedAccepted ProvincialdeliberationProvincialdeliberation
NotificationPublicationNotificationPublication
AcceptedAccepted
Not acceptedNot accepted
New CaledonianGovernment
New CaledonianGovernment
Not acceptedNot accepted End of the procedureEnd of the procedure
8 days
8 days
Eventual procedure
2 months
3.1. Main past and current extracted products
Nickel
Geological Control : Ultramafic Terrane alteration
Rocks : Laterite, saprolite, limonite, garnierite
Minerals : Ni-bearing phyllosilicates (nontronite, népouite, pimelite, willemseite,
pecoraite), uvarovite, pentlandite, heazlewoodite, violarite, millerite, nickel,
awaruite, orcelite, vaesite, Ni-bearing forsterite
Companies : Société Le Nickel; Société Minière du Sud Pacifique; Société des Mines
de la Tontouta; Société Minière Georges Montagnat; JS Berton Mines; Inco;
Falconbridge
Quantity : 7Mt of Nickel Ore
40% are processed in New Caledonia with 75000t/yr of ferronickel (80%)
and nickel matte (20%).
Geology
Nickel ores are formed by the alteration of the peridotite massif. This
geological process is mainly based on the mobility of silicon and magnesium
compared to nickel and cobalt during leaching of the serpentinized peridotite.
The primary mineral in this process is fosterite [(Mg,Fe)SiO4] . This
magnesian olivine which is also composed of small amounts of iron, contains
approximately 0.3% of nickel and 0.01% of cobalt. Under wet tropical conditions, this
olivine is not stable and decomposes into clays and other phyllosilicates (serpentines,
chlorites) which cover most of ultramafic massifs. During these hydration reactions,
35
some silica and magnesium are leached by the water and the newly formed minerals
are enriched in non-mobile element such as nickel.
The development of a Ni-enriched laterite profile needs the right conditions.
The climate must be warm and wet, such as tropical and equatorial areas covered by
rainforest or humid savannah. The other main factors controlling laterite formation
are well developed topography and drainage to avoid stagnant water and to provide an
efficient process to remove soluble elements. Additionally, the development of
important silicate laterite is promoted by tectonic uplift and the composition and
structure of the parent rock (Elias, 2002). All these conditions occur together in New
Caledonia, facilitating the formation of extensive nickel-bearing laterite.
The first facies to appear during laterization is a nickel-bearing limonitic layer
overlying the serpentinized peridotite. As the alteration continues, a part of the nickel
contained in this zone, is transported further down the weathering profile and reacts
with silica in solution to form the nickel-rich saprolite. During this same process, the
iron crust forms at the surface by a complete leaching of all the major elements except
iron. In some places, the saprolite is so enriched that green garnieritic pockets and
veins are found. Garnierite is a mix of true nickel silicates and has a very high grade
in nickel, from 10 to 30% Ni (Fig. 17). However, since its intense exploitation in the
beginning of the last century, this replacive rock has become rare.
Fig. 17. Laterite accumulation processes and nickel enrichment (inspired from McFarlane, 1976).
36
The enrichment in nickel of the lower horizons of the lateritic profile is
confirmed until the alteration front of the basement reaches the groundwater table
level. All elements are then dissolved in the water and no further precipitation of
metals occurs.
Mining
Mining activities are confined to lateritic deposits overlying ultramafic
massifs. 17 mines are currently active and the Goro Project should be starting in a few
months (Fig. 18).
At present, there are 6 large companies involved in New Caledonian Mining industry
- Société Le Nickel (SLN) owned by Eramet and processing 45% of the ore
to Doniambo
- Société Minière du Sud Pacifique S.A. (SMSP) owned by the Northern
Province and accounts for 70% of the export.
- Société des Mines de Tontouta (SMT) owned by Groupe Ballande
- Société Minière Georges Montagnat (privately owned)
- New Inco (merging of Inco and Falconbridge)
- Queensland Nickel Inc. owned by BHP Billiton but not carrying out any
mining operations yet.
0 50 100
Ile Art
Poum
TiebaghiEtoile du Nord
KaalaOuazangou Taom
Koniambo
OuatilouTchingou
Plaine des Gaiacs Kopeto
Me Maoya
MoneoCap Bocage
PoroBoulinda
PoyaLe Cap
Bourail
KouaouaBoakaine
Mt Do
NaketyThio Plateau
Thio MissionPort BouquetNingua
Ouenghi N’GoyeTontouta Ouinne
Mt Dore/Plum
Baie N’Go
PronyPort Boise
Haricot NordGoro
Plaine des Lacs
Operating MinesNot in production or closedDoniambo smelter
NOUMEAN0 50 100
Ile Art
Poum
TiebaghiEtoile du Nord
KaalaOuazangou Taom
Koniambo
OuatilouTchingou
Plaine des Gaiacs Kopeto
Me Maoya
MoneoCap Bocage
PoroBoulinda
PoyaLe Cap
Bourail
KouaouaBoakaine
Mt Do
NaketyThio Plateau
Thio MissionPort BouquetNingua
Ouenghi N’GoyeTontouta Ouinne
Mt Dore/Plum
Baie N’Go
PronyPort Boise
Haricot NordGoro
Plaine des Lacs
Operating MinesNot in production or closedDoniambo smelter
NOUMEANN
Fig. 18. Distribution of active and inactive nickel mine in Grande Terre of New Caledonia.
37
Société Le Nickel (SLN)
SLN is mining limonite-saprolite nickel ore from the following opencut
operations : Koumac, Kouaoua, Népoui-Kopéto, Thio and Tiébaghi. SLN is a
consortium of the Eramet Group of France (60%), Société Territoriale Calédonienne
de Participation Industrielle (30%) and Nisshin Steel Co. of Japan (10%) (Resource
Information Unit, 2004).
- Etoile du Nord (Koumac) produces 18% of the total SLN production.
Limonite is also exploited and exported to Australia. This site is operated by Société
Minière Georges Montagnat for SLN.
- Kouaoua is mined by SLN for a saprolitic ore which averaged 2 to 3%
nickel. The ore is conveyed to coastal stockpiles by a single 11km long conveyor. It is
loaded onto carriers at the offshore terminal at a rate of 1200 t/h, the saprolite is then
shipped to the Doniambo smelter. The main site in Kouaoua, called the Méa deposit,
has been exploited since 1977 with an output of 1Mt/yr of sorted ore (Resource
Information Unit, 2004; Mbendi, 2005).
- Népoui-Kopéto Mine reopened in 1994 after more than a decade of closure.
The orebody is a saprolite extracted at a rate of 4Mt/yr then sent to a sorting plant
where the ore is screened, scrubbed and sized onsite and then hydraulically
transported via a 7km long pipeline to the washing plant at the foot of Népoui massif.
The washed ore is stored, blended and shipped to the Doniambo smelter which has an
input of 830 kt/yr (Resource Information unit, 2004).
- Thio is one of the first mines opened in New Caledonia. Mining started in
1880 and by 1999, the mine had produced 900000 tons of nickel from 40Mt of
saprolite. Several sites were operated simultaneously in the past but only Camp des
Sapins and the Plateau des Mines are in operation now. Plateau des Mines itself has
produced 25Mt of ore assaying 3% nickel, making it one of the largest nickel deposit
in the world (Mbendi, 2005). Ore is trucked and then transported by a 7.5km long
cable way to coastal piles. The output is 750 kt/yr with a portion exported to Japan
and the remainder processed at Doniambo.
- Tiébaghi was first mined for chromium-cobalt ores and nickel enrichments
have been discovered relatively recently (around 1970) (Mbendi, 2005). Tiébaghi was
recently acquired by SLN and proved difficult to mine as the iron crust was too hard
for direct extraction and explosives had to be used. Tiébaghi Mine opens directly onto
the Port of Paagoumene. First ore deliveries from Tiébaghi mine to the Doniambo
38
smelter began in September 1998. From 2003 to 2006, plans to extend the Tiébaghi
mine were in place and production was brought from 250 kt/yr in 2003 to 1Mt/yr in
2006 (Resource Information Unit, 2004, Australian Trade Commission, 2007).
JC Berton Mines (JCBM)
Bienvenue opencut mine is owned by JCBM. It is a small scale mining
operation of high-grade saprolitic nickel ore (3.15% Ni) which has been carried out
intermittently for more than 70 years. In 1990, JCBM began mining limonite ore for
exportation to BHP Billiton Ltd.’s Yabulu nickel refinery in Townsville, Australia.
Ore reserves of this deposit should allow the mine to maintain deliveries of 450 kt/yr
wet ore for the next several years (Resource Information Unit, 2004).
Société Minière du sud Pacifique S.A. (SMSP)
This company is mining small size deposits of saprolitic nickel ore at
Boakaine, Kouaoua, Nakéty, Poum, Poya and Ouaco mining centers.
Société des Mines de la Tontouta (SMT)
Mining operations are underway at Karembe, Monéo and Nakéty mining
centers. Gemini S.A. is operating the Nakéty-Bogota Mine for SMT. All the outputs
from these deposits are exported to Townsville smelter in Queensland.
Goro Nickel Project
Inco discovered the Goro deposit in 1969 and acquired the mining rights in
1992. It is an extensive low-grade laterite deposit with the potential to have one of the
lowest cost sources of nickel in the world. In 2001, Inco began discussions with a
number of companies. The French Geological Survey, Bureau de Recherches
Géologiques et Minières (BRGM) obtained a 15% interest (Lyday, 2003).
In May 2005, the shareholding were revised and Goro Nickel is now owned by
Inco (69%), Sumic Netherlands Nickel (a joint venture of Sumitomo Metal Mining
Co. Ltd. and Mitsui & Co.) (21%) and Société de Participation Minière du Sud
Calédonien which are the provincial authorities of New Caledonia, holds 10% (Fig.
19).
39
Goro Nickel Shareholding
New Inco
Sumic Netherlands Nickel
New Caledonian SouthernProvinceNew Caledonian NorthernProvinceLoyalty Islands Province
10% SPMSC
21%
69%
Fig. 19. Goro Nickel shareholding, (Goro Nickel 2006)
The main features of the Goro deposit are its size and its consistent geometry
and mineralogy. Moreover, its localization in a humid area, fractured and drained by
underground water, has created basin morphologies with high metal contents. The
total thickness of the alteration sequence of the Goro Plateau is important and can
reach 60 meters with an average of 40m (Fig. 20). The laterite exploited has a high
content of free water, (up to 50%) and nickel grades higher than Australian deposits
but lower than New Caledonian saprolite. It is mainly for this last reason that the Goro
deposit wasn’t previously exploited.
Fig. 20. Lateritic sequence in Goro area with element content in correlation with the log (modified from Goro Nickel, 2006).
Hydrometallurgical process (Fig. 22) developed by Inco is likely to make this
deposit highly profitable. The mine which should open in late 2007, is designed to
produce 60000 t/yr of nickel and 5000 t/yr of cobalt at full capacity. In a few years,
Goro Nickel could become the world’s biggest producer of low-cost nickel and the
40
lifespan of the Goro Plateau Mine is estimated to be at least 30 years. 57Mt of proven
probable reserves makes it the best undeveloped laterite orebody (Mbendi, 2005) but
it is likely that more than 120Mt of ore is present and exploitable with an average
nickel content of 1.48% and cobalt of 0.11% (Goro Nickel 2006).
Koniambo Project
The Koniambo project is the other major new project. It is being undertaken
by Inco-Falconbridge in a joint venture with SMSP. 49% of the project will be owned
by Falconbridge and 51% by Société Minière du Sud Pacifique (Falconbridge, 2006;
Australian Trade Commission, 2007). A feasibility study for the nickel laterite has
been completed. Nickel is contained in both saprolite and limonite with good grades.
The saprolite orebody contains 142Mt of measured and indicated resources grading
2.12% nickel and 156Mt of inferred resources grading 2.2% Ni. The expected annual
production would be 60000 tons of nickel as ferronickel.
Nickel will be extracted using a new smelting process to produce ferronickel
from the saprolite. In a future extension, 100Mt of nickeliferous limonite with 1.6%
Ni could be exploited by hydrometallurgical processes (Falconbridge, 2006;
Australian Trade Commission, 2007) (Fig. 22).
The capital cost of Koniambo project was US$2.2 billion in September 2004
and the earliest possible start-up is expected in 2009 (Falconbridge, 2006).
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.60 50 100 150 200 250 300 350 400
Quantity of ore (Mt)
Ni g
rade
(%)
Koniambo
Pom East
Bahodopi
Soroako
Goro
Sampala
Murrin Murrin
Weld RangeMt Margaret
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.60 50 100 150 200 250 300 350 400
Quantity of ore (Mt)
Ni g
rade
(%)
Koniambo
Pom East
Bahodopi
Soroako
Goro
Sampala
Murrin Murrin
Weld RangeMt Margaret
41
Fig. 21. Global nickel laterite resources tonnage-grade plot with some important deposits. Triangles are saprolite deposits and circle are limonites (modified from Elias, 2002).
Production
Most of the ore coming from the SLN mines of New Caledonia is transported
to the Doniambo smelter located on the harbour of Nouméa. The current output of this
smelter is 75000 metric tons per year due to an extension in June 2004 which
increased the production by 13000 t/yr. 3Mt of nickel ore are processed every year by
the smelter to produce 80% of ferronickel with an average nickel content of 26 to
32% and the remaining 20% are nickel-cobalt matte carrying 75% nickel (Fig. 22).
Ferronickel is used directly to make stainless steel whereas the matte is shipped to
Eramet’s Le Havre – Sandouville refinery in France. The nickel-cobalt matte is
converted into high-purity nickel metal and salts of nickel and cobalt (Eramet Group,
2005).
As a part of the Koniambo project, Falconbridge Ltd. and its joint venture
partners are planning to build a ferronickel smelter at Koniambo. This smelter would
have a capacity of 54000 t/yr nickel and ferronickel and would use lateritic ores from
the Koniambo massif as a feedstock. Commissioning of the Koniambo smelter is
scheduled for 2009 or 2010 (Jorgenson et al., 2004).
Because of the low-grade laterite exploited by the Goro Project,
pyrometallurgical processes are not suitable. A hydrometallurgical plant with Pressure
Acid Leaching (PAL) process is constructed in Prony area and should start
progressively in 2008 (Goro Nickel, 2006).
Pyrometallurgy Caron process Hydrometallurgy
Feed
Feed
Feed
Ni : >2.00%Co : 0.04%Fe : 20.0%MgO : 25.0%
Ni : 1.80%Co : 0.1%Fe : 25-40%MgO : <12.0%
Ni : 1.30%Co : 0.13%Fe : >40.0%MgO : <5.0%
SaproliteLaterite
SaproliteLaterite
GarnieriteSaprolite
Proc
ess
Pro
cess
Proc
ess
Upgrading
Drying
Reduction Roast
Smelting
Converting
Drying/Grinding
Reduction Roast
Leaching
Cobalt separation
Precipitation
Calcination
Slurring
Acid Leaching
Washing/Neutralization
Refining
Selective precipitation
Nickel oxide spheruleCobalt carbonate
Nickel sinterCobalt matte
FerronickelNickel matte
90% Ni recovery 80% Ni / 40% Co recovery 94% Ni / 90% Co recovery
Prod
uct
Prod
uct
Prod
uct
Pyrometallurgy Caron process Hydrometallurgy
Feed
Feed
Feed
Ni : >2.00%Co : 0.04%Fe : 20.0%MgO : 25.0%
Ni : 1.80%Co : 0.1%Fe : 25-40%MgO : <12.0%
Ni : 1.30%Co : 0.13%Fe : >40.0%MgO : <5.0%
SaproliteLaterite
SaproliteLaterite
GarnieriteSaprolite
Proc
ess
Pro
cess
Proc
ess
Upgrading
Drying
Reduction Roast
Smelting
Converting
Drying/Grinding
Reduction Roast
Leaching
Cobalt separation
Precipitation
Calcination
Slurring
Acid Leaching
Washing/Neutralization
Refining
Selective precipitation
Nickel oxide spheruleCobalt carbonate
Nickel sinterCobalt matte
FerronickelNickel matte
90% Ni recovery 80% Ni / 40% Co recovery 94% Ni / 90% Co recovery
Prod
uct
Prod
uct
Prod
uct
Fig. 22. Main processes for the extraction of nickel out of lateritic rocks.
42
Cobalt
Location : Ultramafic Terrane alteration, Poya
Rocks : Laterite, pods, chromitite
Minerals : Co-bearing phyllosilicates, asbolane, pentlandite
Companies : Inco ; Société Le Nickel
Quantity : by-product of Nickel ore ; 300 t/yr in nickel matte mainly
Geology
Cobalt is enriched in a similar way to nickel. Cobalt is released by alteration
of forsterite in the laterite but geochemical and crystallochemical conditions make it
less enriched than nickel in the saprolite and the transition zone where those metals
occur in phyllosilicates. However, in the lower part of the laterite, just above the
transition zone, precipitations of manganese oxides retain large quantities of cobalt in
dark blue-grey pods of asbolane.
Mining
Asbolane has been extracted since 1890 by underground mining. New
Caledonia was the only producer of cobalt in the world until 1909 when Canadian
mines opened. Asbolane extraction operations slowly declined in the first half of the
20th century, but cobalt was still produced as a by-product of garnierite and saprolite
and follow nickel in the matte during pyrometallurgy processing. At Goro, however,
cobalt will be extracted directly out of the laterite and separated from nickel during
hydrometallurgical processes. The production of this mine should be around 5000 t/yr
of cobalt as a cobalt carbonate.
Chromium
Location : Ultramafic Terrane, transition zone
Rocks : Chromitite, dunito-chromitite, laterite
Minerals : Magnesiochromite, chromite, Cr-bearing spinel
Quantity : 3.85Mt of chromite
Geology
Chromite-bearing pods and layers are common in the ultramafics. They are
especially related with the dunites of the transition zone. Those bodies are interpreted
as accumulative features of basaltic conduits feeding the main magma chamber in an
ocean ridge system (Fig. 24). The two main features which play a major role in
43
chromite concentration are an active upward magma flow in narrow dykes and an
active convection inside the cavities (Lago et al., 1981)(Fig. 23).
These two processes concentrate chromite in elongated pods or layers
depending where the cumulating reaction takes place. Chromitite bodies are
surrounded by a dunitic rim, the result of a reaction between the harzburgite and the
olivine-saturated melt which migrated through these mantle rocks. As harzburgite is a
pyroxene-bearing rocks, these are assimilated in the basaltic melt, following the
peritectical and isothermal reaction : Opx + Liq Olv + SiO2 (liq) which form dunite
and a more silicic melt (Kelemen, 1990).
The chromite deposits of the Tiébaghi area are different from the rest of New
Caledonia. In the southern massif, chromite pods are small and scattered around the
transition zone whereas in the Tiébaghi area, these rocks show large scale alternations
of dunite, chromitite, harzburgites and lherzolites. This is interpreted as the result of
strong fractional crystallization processes forming bodies analogous to large layered
igneous complexes (Moutte, 1979).
Fig. 23. Model of chromitite pods formation in a cavity along magma dykes in ophiolites (modified from Lago et al., 1981)
Fig. 24. Model of the genesis and evolution of chromitite deposits morphology in ophiolites (modified from Lago et al., 1981)
44
Above the transition zone, cumulus chromitite occurs in layers and dykes
which were only locally exploited (Fig. 24). This chromite is poorer in chromium
oxide (40 wt.%) and richer in iron whereas Tiébaghi chromite can reach 63.5 wt.%
Cr2O3. The Southern massif podiform chromite has a lower chromium content with a
slight Cr-Al substitution (Augé, 1988; Augé & Maurizot, 1995).
Mining
Chromitite bodies were first mined in 1878 at Lucky Hill near Plum and
subsequently at Mont Dore and Nakéty. The Tiébaghi deposit was discovered in 1877
and mining started in 1902, first as an opencut (until 1926) and then as an
underground mining operation until 1963. Chromite exploitation restarted in 1980 and
ended in 1990 when the deposit was mined out. 3.3 Mt of massive rich-chromite (54
wt.% of Cr2O3) has been extracted at Tiébaghi. Smaller deposits are known in the
Tiébaghi massif such as at Chagrin, Fantoche, Vieille Montagne and Bellacoscia
(Moutte, 1979)(Fig. 25).
In the southern massif, many small chromitite bodies have been worked such
as at Marais Kiki, Georges Pile, Alice-Louise and La Madeleine. In the Pirogues
River valley, chromian laterite were studied by the BRGM between 1962 and 1975.
These studies have shown that some of the chromium deposits are as big as Tiébaghi
but the chromium contents are lower and the deposits are not economically viable
(CroixduSud.info, 2007).
Mining centersProcessing plants
Poum (Ni)
Tiebaghi (Co,Cr,Ni)
Koumac (Mn,Ni)
Ouaco (Ni)
Koniambo Plant Project
Koniambo (Ni)Pouembout (Gy)Plaine des Gaiacs (Mg)
Nepoui (Ni)Poya (Gy,Mn,Ni)
Moindou (Hc)
Oua tom (Hc)
Uitoe (Gy)
DoniamboPointe Chaleix
Mont Dore (Cr,Ni)Pirogue (Co,Cr,Ni)
Goro Nickel Project
Yate (Cr,Fe)
Ouinne (Ni)
Thio mission
Thio (Ni)
Canala (Ni,Sb)
Poro (Ni)Moneo (Co,Ni)
Tao
Galarino (Au)
Diahot (Ag, Au,Cu,Pb,Zn))Pam
Ag : silverAu : goldCo : cobaltCr : chromiumCu : copperFe : ironGy : gypsum
Hc : hydrocarbonsMg : magnesiumMn : manganeseNi : nickelPb : leadSb : AntimonyZn : zinc
Mining centersProcessing plants
Poum (Ni)
Tiebaghi (Co,Cr,Ni)
Koumac (Mn,Ni)
Ouaco (Ni)
Koniambo Plant Project
Koniambo (Ni)Pouembout (Gy)Plaine des Gaiacs (Mg)
Nepoui (Ni)Poya (Gy,Mn,Ni)
Moindou (Hc)
Oua tom (Hc)
Uitoe (Gy)
DoniamboPointe Chaleix
Mont Dore (Cr,Ni)Pirogue (Co,Cr,Ni)
Goro Nickel Project
Yate (Cr,Fe)
Ouinne (Ni)
Thio mission
Thio (Ni)
Canala (Ni,Sb)
Poro (Ni)Moneo (Co,Ni)
Tao
Galarino (Au)
Diahot (Ag, Au,Cu,Pb,Zn))Pam
Ag : silverAu : goldCo : cobaltCr : chromiumCu : copperFe : ironGy : gypsum
Hc : hydrocarbonsMg : magnesiumMn : manganeseNi : nickelPb : leadSb : AntimonyZn : zinc
Fig. 25. Important historic mining centres of Grande Terre.
45
3.2. Minor deposits
Iron
Location : Ultramafic Terrane alteration; Dunite-transition zone
Rocks : Laterite, pisolithic horizon, ferricrete, magnetitite
Minerals : Hematite, goethite, alumomaghemite, magnetite, valleriite, chromite,
awaruite, pyrite, chalcopyrite, pentlandite, bornite, cubanite, pyrrhotite,
mackinawite
Companies : Société Le Nickel; Inco
Quantity : 75000 t/yr of ferronickel
Geology
High iron contents mainly occur as iron crust on the top of lateritic profiles
(Figs. 17, 20). The iron crusts form a residual rock by the leaching out of other
elements. Phases which are left are hematite, goethite and maghemite. In a few places,
magnetitite bodies have also been described from dunites of the southern massif
(Guillon & Trescases, 1976) but economic exploitation is not feasible because of their
small size.
Mining
Iron is a major impurity in nickel ores and nickel products. Although it is
strongly reduced by various metallurgical processes, the final product remains
ferronickel and iron forms nearly three quarter of the alloy. The use of nickel by the
steel industry is however fully compatible with high iron contents.
Iron as a metal was only exploited out of the lateritic crust from 1938 to 1941
in Goro and the entire production (450 kilotons of ore) was exported to Japan. From
1955 to 1960, mining was undertaken at Prony Bay and the output (3 Mt) was sent to
BHP smelters in Australia. The New Caledonia iron ores are of little interest to the
mining industry.
Manganese
Location : Ultramafic Terrane alteration, Poya
Rocks : Laterite, pods
Minerals : Asbolane, manganite
Quantity : 60000 tons
46
Mining
Small pods of manganese were exploited from the Poya basalts between 1918
and 1922 and from 1949 to 1953. A few thousands tonnes have been produced mainly
from Bourail and Koumac areas (Gineste, 2007) (Fig. 25). Manganese is an important
impurity in nickel and cobalt ores. The main cobalt bearing phase, asbolane, is a wad-
like mineral species which contains up to 45% manganese and a few percents of
cobalt and nickel. This manganese is efficiently extracted during pyro- and
hydrometallurgical processes.
Copper-Zinc-Lead-Silver
Location : Diahot, Ultramafic Terrane
Rocks : Mica schists, magnetitite
Minerals : Chalcopyrite, chalcocite, covellite, digenite, bornite, cubanite, copper,
tenorite, cuprite, valleriite, azurite, malachite, chrysocolle, chalcanthite
Galena, cerusite, anglesite, pyromorphite, wulfenite, aikinite
Sphalerite, Smithsonite
Silver, argentite, jalpaite
Companies : Caledonian Pacific, Base Metals Exploration
Quantity : 7000 tons of Cu extracted from 1872 to 1949
Geology
Copper mineralization mainly occurs in Diahot Terrane as stratiform sulphide
deposits (Fig. 25). These deposits are restricted to defined stratigraphical horizons of
diahot terrane. However, they didn’t reach the same metamorphic conditions and are
therefore hosted in different grade rock. The sulphide ores are usually well laminated
with compositional banding of sulphides, show relict of sedimentary textures and
occur as layers and lenses which are conformable with the host rock. Two kinds of
deposits are distinguished with copper-enriched ore with small amounts of Pb, Zn
(Balade, Murat, Ao, Pilou) and lead-zinc deposits with minor cupriferous minerals
(Mérétrice, Fern-hill) (Fig. 26). In Mérétrice Mine, a secondary enrichment in silver
bearing minerals is observed but silver is also present in solution in galena and
tetraedrite in the main ore. Some gold and tin enrichment are also noticed in this mine
(Gineste, 2007). In Ao mine, strong enrichments in bismuth (bismuthinite, aikinite)
also occur in the copper ore (Briggs et al., 1977).
47
The host rock protolith is mainly acidic rhyolitic tuff. However, black
carbonaceous phyllites seem necessary for the formation of the deposits. These latter
rocks are rich in pyrite and show sulphide concentrations in layers of a few
centimetres thick. In Balade Mine, an iron-rich non-sulphide metasediments zone is
described and show many similarities with kuroko-type deposits. However, the high
pressure metamorphism of the Diahot terrane makes assumptions difficult to make
regarding the metallogeny of these deposits. The presence of black shales relates these
more to Rio Tinto-type deposits whereas some features are more sedimentary-
exhalative (Briggs et al., 1977).
Fig. 26. Map of the Diahot region with the location of Cu-Pb-Zn mines with respect to regional structures and the progressive metamorphic sequence modified from Briggs et al., 1977)
Mining
Copper was found in the northeastern part of Grande Terre, in Diahot valley,
near Ouégoa in 1872 and many small mines opened such as Balade, Bruat and Murat
and later Pilou-Nemou, Mérétrice and Ao mine, famous for its azurite deposit.
Copper exploitation started in 1873. Production from Balade, Bruat, Pilou-
Nemou and Méretrice was sent to smelting plants in Pam, Dilah and Tao. The copper-
lead-silver mining activity ended in 1931 when the Société Minière du Diahot was
declared bankrupt. In 1949, some mining activities were resumed to exploit 9000
48
tonnes of ore still available but only 1750 additional tonnes have been extracted. The
metal grade of Méretrice mine is 15-20% Pb and 25-30% Zn with important amounts
of copper and silver (100g/t) in the sulphurised zone. In the oxidation zone, the ore is
richer in lead (25-30%) and lower in copper (15-25%) with 400 g/t of silver and up to
3.7g/t of gold (Briggs et al., 1977; Gineste, 2007). Other deposits are richer in copper
and iron sulphides (Briggs et al., 1977).
At the end of the nineties, an intensive program of ground geophysics was
started for the Méretrice Zinc Project. The purpose of survey was to identifiy drilling
targets along a 4km belt of potential stratabound, sediment hosted massive sulphide
Cu-Zn-Pb-Ag mineralisation (Mining Exploration News, 1997). Intense anomalies
have been detected as bodies of 4500 meters long and 1500 meters wide near the
Méretrice Mine (Mining Exploration News, 1998). According to BRGM studies,
25000 to 30000 tonnes of ore (25%Zn, 15%Pb) is still available.
3.3. Subeconomic enrichments
Gold
Location : Pouébo, Diahot, Poya, Ultramafic Terrane, Central Chain
Rocks : Quartz veins
Minerals : Gold, awaruite, pyrite, arsenopyrite
Companies : Base Metals Exploration
Quantity : 300kg
Mining
Gold was first discovered in 1863 in Pouébo but the most important discovery
was at Fern Hill in 1870 where the site produced 212kg of gold from 1873 to 1900.
Other localities also produced gold such as Grosses Gouttes near St Louis, Queyras
(La Foa), Edison (Pouembout), Honfleur (Poya) and at Nakéty (Fig. 25). However not
all these localities show economic grade (Croixdusud.info, 2007). Nonetheless, in
many quartz veins throughout New Caledonia, small particles of gold can be found as
inclusions (Noesmoen, 1971).
In the late nineties, a drilling campaign has identified 16Mt of ore average
6.1g/t Au and 12Mt of ore average 3.57g/t Au in Fern hill Mine and 5Mt at 5.86 g/t
Au in Nundle (Mining Exploration News, 1997). In November 2000, six large gold
and base metals prospects (Méretrice, Nakéty, Fern Hill, Edison, Devaux, Azema and
49
St Louis) were purchased by Base Metals Exploration NL of Australia from Quadtel
Ltd for $12.5 million (Mining Exploration News, 1998). However, by year end 2003,
Base Metals Exploration was no longer active in drilling and the sites were idle
(Resource Information Unit, 2004).
In the ultramafic terrane, a geochemical study has investigated the enrichment
processes of gold and copper. Cu and Au decrease with the increasing residual
character of the mantle rocks. In the cumulative zone, Cu is strongly enriched in
basaltic rocks whereas early cumulates (dunites and pyroxenites) have high Au
contents (Dupuy et al., 1981b). However, concentrations in those rocks and
chromitites are significantly lower than those in layered intrusions such as Bushveld
and are unlikely to be exploitable (Fig. 27).
0
50
100
150
200
250
300
Plagioc
lase L
herzo
lite
Spinel
Lherz
olite
Harzbu
rgite
Dunite
Dunite
Whe
rlite
Orthop
yroxe
nite
Cumula
te Gab
bro
Dolerite
dike
Basalt
flow
Ave
rage
abu
ndan
ce (p
pm)
CopperGoldCobaltVanadium
Non-cumulate ultramafic rocks
Cumulate and basic rocks
0
50
100
150
200
250
300
Plagioc
lase L
herzo
lite
Spinel
Lherz
olite
Harzbu
rgite
Dunite
Dunite
Whe
rlite
Orthop
yroxe
nite
Cumula
te Gab
bro
Dolerite
dike
Basalt
flow
Ave
rage
abu
ndan
ce (p
pm)
CopperGoldCobaltVanadium
Non-cumulate ultramafic rocks
Cumulate and basic rocks
Fig, 27. Average abundances of some metals in ultramafics rocks (Dupuy et al., 1981b)
Platinoids
Location : Ultramafic Terrane, Quaternary placers
Rocks : harzburgite; chromitite; alluvial placers
Minerals : Numerous alloys, sulphides and oxides of Pt, Ru, Rh, Ir, Os
Geology
50
PGE mineralization was studied and investigated in the 1980’s and 1990’s in
the southern massif and Tiébaghi area. Some sulphide-rich zone of the harzburgites
with anomalous concentrations of PGE and heavy-mineral concentrates have high
concentrations of platinoids (1835ppb Ir, 1527ppb Rh, 9718ppb Pt, 11494ppb Pd and
988ppb Au) (Augé et al., 1999). Awaruite seems to be a preferential host for PGE in
this system but some Ir-Ru-Os alloys are identified in the Southern Massif and laurite
and erlichmanite have been described from the Tiébaghi chromitite (Augé &
Maurizot, 1995).
Pirogues River mineralization shows two types of enrichment in PGE. The
main enrichment in PGE occurs in the ultramafic transition zone, with a strong
correlation with chromitite layers and dykes. Average concentrations found for these
chromium-bearing rocks are 3882ppb Pt, 269ppb Pd, 350ppb Rh, 192ppb Ru and
248ppb Ir with higher concentrations in massive chromitite dykes (Augé & Maurizot,
1995). Elsewhere in the Pirogues River area, there are no PGE concentrations in the
mantle chromitite pods but in placers derived from these chromitite layers, PGE-
bearing minerals are freed from their chromite matrix. Therefore, this alluvial deposit
is mainly composed of alloys and sulphides of PGE whereas chromitite ultramafic
layers are more characterized by PGE oxides and PGE-bearing base metal sulphide
inclusions (Augé & Legendre, 1994). In placers of the Pirogues River, average
concentrations of bulk sediments are 500ppb Pt but obtaining concentrates is a
process of screening, density and magnetic separation (Augé & Maurizot, 1995).
Molybdenum & Tungsten
Location : “Ultramafic Terrane”
Rocks : Granitic and pegmatitic intrusions
Minerals : Molybdenite, wulfenite, scheelite
Geology
In the granodiorite batholith north of La Coulée, molybdenite occurs in
association with chalcopyrite in quartz veins. Tungsten ore is also present as scheelite
in quartz breccias of the Thy valley where the granodiorite is in contact with
Cretaceous sedimentary rocks. Small amounts of scheelite have been described by
Guillon & Trescases (1976) from many small granitic and pegmatitic intrusions
crossing the ultramafic terrane.
51
Antimony
Location : Central Chain
Rocks : Quartz veins
Minerals : Stibnite, valentinite, senarmontite
Mining
Between 1883 and 1884, 1600 tonnes of ore (34% Sb) have been extracted out
of the Nakéty Mine. Sibnite occurs with some amounts of gold and sphalerite in
quartz veins (Gineste, 2007) (Fig. 25).
3.4. Non metal resources
Coal
Coal measures occur in New Caledonia but the coals are thin, discontinuous
folded, and low quality. Small scale mining activities were undertaken in the last
century at Nondoué (Dumbéa valley) and Moindou (croixdusud.info, 2007).
Oil
Oil exploration was undertaken between 1907 and 1911 at Ouen Toro near
Nouméa (750m deep borehole) and in Koumac area between 1913 and 1921. Two
600m deep boreholes were also drilled at Gouaro (Bourail) in 1951 but these too were
unsuccessful. In 1999-2000, a 1600m deep borehole was drilled in Gouaro by Victoria
Petroleum N.P. and Sun Resources N.L. but was dry (Mining Exploration News,
1998). A new phase of oil exploration is underway offshore and recent work has
indicated favourable structures in the Fairway Basin (North-eastern part of New
Caledonia basin), in 2000m of water.
Limestone and other rocks
Limestone is extracted for local purposes in some places and processed at the
cement plant of Société des Ciments de Numbo in Nouméa. This industry has an
average growth of 4% (Holderbank, 1999; Lyday, 2003). Construction materials are
also exploited locally from several small quarries (Lyday, 2003).
52
4.0. References Aitchison, J.C. & Meffre, S., 1992. New Caledonia : A tectonic collage in the southwest Pacific. 29th International Geological Congress, Kyoto, Japan, Abstracts, 2, p255. Aitchison, J.C., Clarke, G.L., Meffre, S. & Cluzel, D., 1995. Eocene arc-continent collision in New Caldeonia and implications for regional southwest Pacific tectonic evolution. Geology, 23, 2, p161-164. Aitchison, J.C., Ireland, T.R., Clarke, G.L., Cluzel, D., Davis, A.M. & Meffre, S., 1998. Regional implications of U/Pb SHRIMP age constraints on the tectonic evolution of New Caledonia. Tectonophysics, 299, p333-343. Ali, J.R. & Aitchison, J.C., 2000. Significance of paleomagnetic data from the oceanic Poya Terrane, New Caledonia, for SW Pacific tectonic models. Earth and Planetary Science Letters, 177, p153-161. Ali, J.R. & Aitchison J.C., 2002. Paleomagnetic-tectonic study of the New Caledonia Koh Ophiolite and the mid-Eocene obduction of the Poya Terrane. New Zealand Journal of Geology & Geophysics, 45, p313-322. Aronson, J.L. & Tilton, G.R., 1971. Probable Precambrian detrital zircons in New Caledonia and Southwest Pacific continental structure. Geological Society of America Bulletin, 82, p3349-3356. Auboin, J., Mattauer, M. & Allègre, C., 1977. La couronne ophiolitique périaustralienne : un charriage océanique représentatif des stades précoces de l’évolution alpine. Comptes Rendus de l’Académie des Sciences Fr. Série D, 285, p953-956. Augé, T., 1988. Platinum-group minerals in the Tiébaghi and Vourinos ophiolitic complexes : Genetic Implications. The Canadian Mineralogist, 26, p177-192. Augé, T., & Legendre, O., 1994. Platinum-group element oxides from the Pirogues ophiolitic Mineralization, New Caledonia: Origin and significance. Economic Geology, 89, p1454-1468. Augé, T., & Maurizot, P., 1995. Stratiform and alluvial platinum mineralization in the New Caledonia Ophiolite complex. The Canadian Mineralogist, 33, p1023-1045. Augé, T., Cabri, L.J., Legendre, O., McMahon, G. & Cocherie, A., 1999. PGE distribution in base-metal alloys and sulphides of the New Caledonia ophiolite. The Canadian Mineralogist, 37, p1147-1161. Australian Trade Commission, 2007. Australian Government, Mining to New Caledonia. Updated 31/07/07. Accessed 21/08/07. URL : http://www.austrade.gov.au/Mining-to-New-Caledonia/default.aspx Auzende, J.M, Pelletier, B. & Eissem, J.P., 1995. The North Fiji Basin. Geology, structure and geodynamic evolution. In: Taylor, B., Back-arc basins: tectonics and magmatism, Plenum, NY. P139-175. Avias, J. & Gonord, H., 1973. Existence dans la chaîne centrale de la Nouvelle-Calédonie (bassin de la Boghen et région du col d’Amieu) de horsts de formations plissées a métamorphisme principal d’age ante-permien et très probablement hercynien. Comptes Rendus Hebdomadaires des Seances de l’Académie des Sciences, Série D, 276, p17-18. Balance, P.F. & Campbell, J.D., 1993. The Murihuku arc-related basin of New Zealand (Triassic-Jurassic) In: Balance, P.F. ed. South Pacific sedimentary basins; sedimentary basins of the world 2. Amsterdam, Elsevier. P21-33. Black, P.M., 1977. Regional high-pressure metamorphism in New Caledonia; phase equilibria in the Ouégoa district. Tectonophysics, 43, p89-107. Black, P.M., 1995. High-Si rhyolites and shoshonitic volcanics; a late Cretaceous bimodal association, Nouméa basin, New Caledonia. In: Pacrim’95 Congress, Auckland, Proceedings Volume, p55-58. Black, P.M. & Brothers R.N., 1977. Blueschist ophiolites in the melange zone, northern New Caledonia. Contributions to Mineralogy and Petrology. 65, p69-78. Black, P.M., Brothers, R.N. & Yokohama, K., 1988. Mineral paragenesis in eclogite-facies meta-acidites in northern New Caledonia. In : Eclogites and eclogite-facies rocks. Developments in Petrology, 12, p271-289. Black, P.M., Itaya, T., Ohra, T., Smith, I.E., Takagi, M., 1994. Mid-Tertiary magmatic events in New Caledonia: K-Ar dating on boninitic volcanism and granitoid intrusives. Geoscience Report of Shizuoka University, 2, p49-53.
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Cluzel, D., Aitchison, J.C., Black, P.M. & Picard, C., 1999. Origin and fate of Southwest Pacific marginal basins; an appraisal from New Caledonia. In: Baldwin, L. & Lister, G.S., Penrose Conference, Mid-Cretaceous to recent plate boundary processes in the Southwest Pacific, Abstract Volume, p77-79. Cluzel, D. & Meffre, S., 2002. L’unité de la Boghen (Nouvelle-Calédonie, Pacifique sud-ouest) : un complexe d’accrétion jurassique. Données radiocronologiques préliminaires U-Pb sur les zircons détritiques. Comptes de l’Académie Royale des Sciences, Geoscience, 334, p867-874. Cluzel, D., Paquette, J.-L. & Trotet, F., 2002. Late Oligocene granodioritic plutonism in New Caledonia : A clue for post-obduction slab detachment. 2002 Western Pacific Geophysics meeting, Eos Transactions, American Geophysical Union, 83, p87. Cluzel, D., Bosch, D., Paquette, J.-L., Lemennicier, Y., Montjoie, P. & Ménot, R.-P., 2005. Late Oligocene post-obduction granitoids of New Caledonia : A case for reactivated subduction and slab break-off. The Island Arc, 14, p254-271. Cluzel, D., Meffre, S., Maurizot, P. & Crawford, A., 2006. Earliest Eocene (53Ma) convergence in the Southwest Pacific : evidence from pre-obduction dikes in the ophiolite of New Caledonia. Terra Nova, 18, p395-402. Collot, J.-Y. & Missègue, F., 1977a. Gravity measurements in Loyalty Archipelago, southern New Caledonia and the Isle of Pines. International symposium on geodynamics in south-West Pacific, 1977, p125-134. Collot, J.-Y. & Missègue, F., 1977b. Crustal structure between New Caledonia and the New Hebrides. International symposium on geodynamics in south-West Pacific, 1977, p135-144. Collot, J.-Y., Rigolot, P. & Missègue, F., 1988. Geologic structure of the Northern New Caledonia ridge, as inferred from magnetic and gravity anomalies, Tectonics, 7, p991-1013. Coudray, J., 1976. Recherche sur le Néogène et le Quaternaire marin de la Nouvelle Calédonie. Contribution de l’étude sédimentologique à la connaissance de l’histoire géologique post-Eocène. Expédition française sur les récifs coralliens de Nouvelle Calédonie, Fondation Singer-Poulignac. Crawford, A.J., Meffre, S. & Symonds, P.A., 2003. 120 to 0 Ma tectonic evolution of the southwest Pacific and analogous geological evolution of the 600 to 220 Ma Tasman Fold Belt System. Geological Society of America Special Paper, 372, p383-403 Croixdusud.info, 2007. Nouvelle-Calédonie – Economie – Mines. Accessed : 21/08/07. URL : http://www.croixdusud.info/economie/mines.php Dana, J.D., 1873. In: Gaines, R.V., Skinner, H.C., Foord, E.E., Mason, B. & Rosenzweig, A., 1997. Dana’s New Mineralogy. John Wiley & sons, Inc. Daniel, J., Dugas, F., Dupont, J., Jouannic, C., Launay, J., Monzier, M. & Recy, J., 1976. La zone charniere Nouvelle-Caledonie—Ride de Norfolk (S.W.Pacifique) ; resultats de dragages et interpretation. Cahiers – ORSTOM, Serie Geologie, 8, p95-105. Davies, H.L. & Smith, I.E., 1971. Geology of eastern Papua. Geological Society of America Bulletin, 82, p3299-3312. de Jersey, N.J. & Grant-Mackie, J.A., 1989. Palynofloras from the Permian, Triassic and Jurassic of New Caledonia. New Zealand Journal of Geology and Geophysics, 32, p463-476. Dubois, J., 1969. Contribution a l’etude structurale du Sud-Ouest du Pacifique d’apres les ondes sismiques observees en Nouvelle-Caledonie et aux Nouvelles-Hebrides. Annales de Geophysique, 25, 4, p923-972. Dubois, J., Launay, J. & Recy, J., 1974. Uplift movements in New Caledonia-Loyalty Islands area and their plate tectonics interpretation. Tectonophysics, 24, p133-150. Dubois, J., Dugas, F., Lapouille, A. & Louat, R., 1975. Fosses d’effondrement en arriere de l’arc des Nouvelles-Hebrides ; Mecanisms proposes. Revue de Geographie Physique et de Geologie Dynamique, 17, p73-94. Dubois, J., Recy, J., Montadert, L. & Jouannic, C., 1976. Evolution of plate boundaries in time ; examples in the South-West Pacific. International Geological Congress, 25, 1.3, p82. Dupont, J., Launay, J., Ravenne, C. & De Broin, C.E., 1975. Données nouvelles sur la ride de Norfolk (Sud-Ouest Pacifique). Comptes Rendus hebdomadaires des séances de l’Académie des Sciences, Série D., 281, p605-608.
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