The recent Nickel Copper intersections uncovered in a area with...

The recent Nickel Copper intersections uncovered in a area with no or very little outcrop is a good result for the geologists and geophysicists. The Fraser Range Complex is a layered mafic and ultramafic intrusion which has been a tantalising target for over 40 years but up until now there has been nothing substantial found. In this type of deposit the most prospective part is the ultramafics (high in iron and magnesium and low in alumina and alkali metals). Most of the outcrop is mafic such as gabbro (which is more resistant to weathering) whereas the ultramafics are beneath a thick overburden of much younger sediments. This type of occurrence may also have a significant grade of platimum group elements. The basic principle of mineralisation is that as the magma cools the higher temperature minerals form first and the lower temperature ones form last in what ever space there is. ( Its a lot more complicated than that but this is for the average forum reader) In the right magma condiitons of chemistry, temperature and pressure the suplhur will collect nickel and copper to form pentlandite, chalcopyrite etc and PGE should precipitate from the remaining melt at the same location. Generally speaking the larger the initial body of magma the better chance of an economic grade being fractionated from it. In some deposits such as the Great Dyke in Zimbabwe the mineralisation is just below the contact between the mafics and ultramafics. I don't know what the geology of the SIR mineralisation is but it will be interesting to see if the rest of the geophysical targets come up with similar mineralisation. The Giles complex in central Australia is also worth a look but thats another story.