Until the next NR, some intellectual stuffThis is from geoprof...as you will see, he has a background worth listening too. This of course was posted on the agora board where real info is shared...
I would like to offer the following, which I hope will provide a much better understanding of the above. It is based on my own experience, education and the work of many geoscientists, especially Tony Naldrett, over the years.
Magnesium-rich, ultramafic/mafic magmas exist deep within the earth, probably within the mantle. They are by nature, more Ni, Cr, Cu and PGM rich than other more felsic (e.g. granitic) magmas which are probably formed by remelting of existing crust. For one reason or another, they rise and as they rise they may come into contact with sulphur-rich material as they entire the crustal zone. Being a high temperature liquid, these magmas can dissolve sulphur. As they continue to rise, they begin to cool and reach a temperature where they become sulphur supersaturated. Once that occurs, liquid sulphur-rich blebs begin to separate from the parent magma and because Ni, Cu and PGMs are "chalcophile", i.e are drawn to sulphur, like bees to honey, they become dissolved in the sulphide blebs and more or less leave the silicate magma. With more cooling, grains of chromite and olivine will begin to crystallize along with the Ni/Cu/PGM-rich sulphide blebs. Due to density considerations, all three will tend to sequentially settle to the bottom of any magma chamber. Hence, the volume of the original, parent ultramafic magma is a major determinant of the final amount of Ni, Cu, Cr and PGMs in basal accumulations upon solidification. Final tonnages and grades depend on the amount of sulphur originally assimilated, the volume of the parent ultramafic magma and the cooling rate.
Again, the volume of peridotite (representing at least a portion of the parent magma) compared to the volume and grades of sulphide mineralization observed to date at the Double Eagle property is much too small to have generated the amount of Ni, Cu, PGMs and Cr in the mineralization which has been intersected to date. I think that we are observing only a portion of what has been the result of a very efficient crystallization process, brought on by a relatively slow cooling, of much larger body of the parent magma which remains to be discovered. Hopefully, that body will still contain basal accumulations of Ni/Cu/PGM mineralization comparable to what we have seen on the DE property to date.