Plaine des Lacs District - Goro, Prony
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A number of major oxide laterite deposits are found in the Prony / Plaine des Lacs district, in the south-eastern section of the
island of New Caledonia. These include Goro and Prony. Prony is located near the south-eastern tip of the island of New Caledonia, ~40 km east of Nouméa (#Location: 22° 17' 34"S, 166° 48' 51"E). Goro is a further 15 km east (#Location: 22° 17' 28"S, 166° 58' 1"E).
For details of the geological, structural and tectonic setting of New Caledonia, see the Plateau/Thio, Nakety, Canala, etc record. record.
The Goro Project, which is the largest of these oxide laterites, is described here as an example of the deposits of the district.
The deposit is an oxide laterite in contrast to the silicate laterites of most of the other significant mines on the island. As such it is amenable to treatment by pressure acid leach treatment, rather than the ferro-nickel and matte smelters used for the silicate ores.
Goro is developed over the same peridotite mass as the other main deposits on New Caledonia. It is composed of a thick limonite and thin underlying saprolite, and occurs on a plateau with deep lateritisation, protected by an iron cap cover. It has a lower MgO and higher Co content than the silicate ores of the island.
A typical profile comprises, from the surface:
• An upper thin iron cap, generally <5 m thick,
• A limonite over-burden layer that may be 15 m thick, with a zone of iron shot in its upper sections marking a transition to the overlying iron cap. This limonite overburden carries around 0.8 to 1.2% Ni, 0.01 to 0.06% Co, 40 to 50% Fe, 1 to 2% SiO2, 0.5 to 2% MgO.
• The limonite ore zone which is more than 10 m thick carrying 1.2 to 1.7% Ni, 0.1 to 0.5% Co, 40 to 50% Fe, 3 to 10% SiO2, 0.6 to 3% MgO.
• A transition zone up to 5 m thick to the underlying saprolite.
• A saprolite and saprock zone that may be around 5 m thick, which assays 1.2 to +3% Ni, 0.05 to 0.5% Co, 15 to 40% Fe, 20 to 40% SiO2, 10 to 30% MgO.
The drill indicated resource at Goro in 2000 was 165 Mt @ 1.6% Ni, 0.16% Co, with an initial
proven mining reserve of 47 Mt.
In 2005 reserves and resources were (Inco, 2006):
Proven reserves - 96 Mt @ 1.34% Ni
Probable reserves - 24 Mt @ 2.01% Ni.
Measured resources - 39 Mt @ 1.31% Ni,
Indicated resources - 36 Mt @ 1.68% Ni
Inferred resources - 128 Mt @ 1.7% Ni.
Total resources in 2011 (USGS< 2011), were:
126.4 Mt of ore grading 1.44% Ni and 0.11% Co
The most recent source geological information used to prepare this summary was dated: 2001.
Record last updated: 21/12/2015
This description is a summary from published sources, the chief of which are listed below.
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