A lot of armchair and supposed expert geologists want to make much of le grande differance la between different rocks which turn out to be of roughly the same parentage, age, depth of mantle origin and general mineralogical character. If they even tend to be found as a family in the same hosts rocks, some schools of geology want to differentiate them widely. Many have made much of the troctolite at Voisey's Bay saying it is deeply significant, and ignore the nearby and possibly co-eval ophiolitic terrane. Troctolite in gabbroic areas near nickel copper showings is common from Newfoundland to Ontario, to Manitoba. It is not a rare rock, in Sudbury, Thompson, Thunder Bay or elsewhere. They also differentiate the rocks of Newfoundland's west coast very greatly from the rocks of east Labrador with great cause to do so. The age differences in our opinion given the other similarities of mineralogical emplacement are not that great a problem.
Broad facts of greater similarity amongst nickel rocks the world round still remain. Much of the world's nickel is emplaced in either varieties of gabbro, komatiites, serpentinized/non serpentinized dunites, or peridotites. These rocks are often called intrusives but many have the high level, fined grained nature of flows, and in some cases have been identified as such. They are almost always middle to late proterozoic and "intrude" or overlie, banded orthogneisses of elevated metal and sulfur content. The host rocks of the Ni deposits are mafic to ultramafic gabbroic to perodotitic melts of various fractionations of the mantle rocks. As well, the Ni deposits seem to adhere to volcanic terranes and are not found in pure intrusive areas often. The fine grained nature of the perditotites the Ni is associated with or seems to fractionate from, contrasts sharply to any pure intrusives in the area. What many feel is that these high level peridoties, either subaqueous or alpine, are the roots of extrusives flows. In many cases such as at the Redstone, and in other Timmins nickel deposits, this cannot be denied. The Timmins stuff is at the base of perdotitic and komatiitic flows. Kambalda type as it were.
The Tasiuyak gneiss, of elevated sulfur and nickel content most definitely does traverse the entire land mass from Labrador's southern shore to Ungava Bay. It is associated and identified pervasively with nearly all the nickel showings drilled for hundreds of miles in that region.
What some geologists want to say about nickel deposits is that they are of entirely different type depending on the MgO content, copper, Pt content and Pt-Pd ratios, and whether the rocks seem to volcanic or instrusive. I will grant them these differences, but the similarities are even more striking. It is my opinion that when all the evidence is in the level of the emplacement of nickel in many cases will be seen to be remobilizates at a higher crustal level, and the initial mantle derivation does not have to have been of ore character. The whole fiction of magma chamber fractionation and pure intrusive emplacement may some day have to go by the board. I think in time the obvious sedimentary nature of the Sudbury deposits will someday be seen too. All the nickel deposits I have seen have either a remobilized shear or vein nature to them, or they are associated with extremely fine grained high level rocks that could be for the most part subaqueous extrusives. Their immediate surrouding rocks they are in direct contact with are almost exclusively tuffs, sediments, and volcanics. The ubiquitous gneissic association has never been satisfactorily explained. Gneisses are the rocks that predominate at a depth of about 10 KM's below the intial crustal diapirs and sediments we overlie.
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