Fraser Range Ni-Cu-PGE sulphide deposits

Weekend Reading..........

For Fraser Range Ni-Cu-PGE sulphide deposits see - World map showing magmatic Ni-Cu-PGE sulphide deposits having resources and/or production greater than 100,000 tonnes of ore. (Figure 1 on Page 206) - 2nd Page of the 18 Pages here:-

http://www.d.umn.edu/~pmorton/geol5350/2009/deposit_synthesis.ni_cu_pge.eckstrand_hulbert.pdf

MAGMATIC NICKEL-COPPER-PLATINUM GROUP ELEMENT DEPOSITS

In total there are 142 Ni-Cu-PGE deposits and districts in the world for which grade and ore tonnage data have been reported that contain more than 100 000 tonnes of resources and/or production, (as shown in Figure 1. above)
Among the global deposits/districts there are 51 Ni-Cu deposits/districts and 5 PGE deposits/districts with greater than 10 million metric tonnes (MT)
There are 13 Ni-Cu deposits/districts and 2 PGE deposits/districts with greater than 100 Mt.
Which are we in ??......
Some Ni-Cu-PGE deposits occur as individual sulphide bodies associated with magmatic mafic and/or ultramafic bodies.
Others occur as groups of sulphide bodies associated with one or more related magmatic bodies in areas or belts up to tens, even hundreds of kilometres long.
Such groups of deposits are known as districts (e.g. Sudbury, Thompson, Noril’sk-Talnakh, Kambalda, Raglan).
Magmatic Ni-Cu sulphide deposits provide most of the Ni produced in the world and continue to have substantial reserves.
Magmatic PGE deposits and Ni-Cu sulphide deposits are the source of essentially all of the world’s platinum group elements.
Lateritic Ni deposits, formed from the weathering of ultramafic rocks, are also substantial sources of Ni, and have global reserves greater than those of Ni-Cu sulphide deposits.
Lateritic Ni deposits do not occur in Canada, but will probably in time become the main source of nickel.
Placer deposits have also been mined for Pt in many parts of the world, but are of little
significance in Canada and appear to have little potential elsewhere.

Knowledge Gaps
One of the gaps in our knowledge of Ni-Cu sulphide deposits is in knowing the most important factor in triggering sulphide saturation in a given magma.
Certain things are clear.
The magma must have a sufficient dissolved content of Ni, Cu, and PGE.
Once a liquid sulphide is formed, it will tend to equilibrate with the magma, and this means acquiring the Ni, Cu, and PGE from the magma according to the partition coefficients for those elements.
It also is clear that much of the S in magmatic Ni-Cu sulphide deposits has been derived from sulphidic wall rocks, commonly pyritic sediments. Thus, addition of S to the magma by incorporation of such material leads to sulphide saturation.
However, it is also known that by increasing the silica content of the magma through incorporation of siliceous wall rock, the solubility of sulphide in the magma is decreased, thereby producing sulphide saturation.
It remains unclear which of the two mechanisms is the more critical in producing sulphide saturation.
The significance for exploration is whether it is essential to have wall rock rich in sulphide as a source of S in order to better evaluate a priori the nickel potential of a given mafic/ultramafic body.
Existing evidence tends to favour the sulphidic wall rock theory, but more investigation of the settings of known nickel sulphide deposits is needed in order to evaluate the importance of the alternative theory.
So are we Magmatic, Lateritic or Placer ???.......
GL – Oilf.