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Gold/Mining/Energy : Trump's 12 Diamond Picks, Discussions Limited -- Ignore unavailable to you. Want to Upgrade?

To: George J. Tromp who wrote (1737)	12/6/1998 11:20:00 AM
From: E. Charters	Respond to of 2251

It doesn't matter which rock type you are in for kimberlite evolution. This has no good theoretical or practical correlation. Discerning their magnetic signatures is another matter. This is also a mix up. In some volcanic areas, ie: the Blake River Volcanics of Kirkland Lake the magnetic background is washed out, so the diatremes stand out that are magnetic. In others the sediments have lower background so the contrast is better there (James Bay Lowlands.) But certain sediments may be very busy magnetically. And granitic areas can be busy too (NWT) (although here the sediments are busier than the granites). And to top it off many kimberlites have no or negative magnetic signature. In the north however the magnetic gradient increases so the magnetic rocks start to stand out in contrast and in total magnetism more and more. A kimberlite at the equator might have a signature of 20,000 Gamma, but in Victoria Island that same kimberlite may be 70,000 Gamma. To search for them you have to use a combination of magnetic, infrared, conductive and visible light patterns. (there is not a single magnetic kimberlite in Nigeria) The correlation with NW faults and dykes is not fortuitous but is only half the story. It would be a mistake to go crazy in a NW direction thinking that you are chasing the grail. In fact the opposite may be more true. I don't want to reveal too much here but there is literature on the topic of faults that clearly illustrates the actual pattern and as many of the veterans think they know ,I will let them be happy in their ignorance. Suffice to say a kimberlite dyke is most often NE in direction in Canada. In actual fact the stress on the crust is greatest at the equator and you would expect more faulting and seismic activity there. But the crust should be thickest there too. But it seems there are faults everywhere and kimberlites and diamonds distributed all over the globe. Since Mitchell of Lakehead more or less defined the lamproitic regime and refutes N. Rock's thesis that the whole mafic group is related as variants ie: lamprophyres, lamproites, etc, I tend to his definitions of lamproites as tri-modal species ie: olivine-diopside-phlogopite lamproite that are actually not kimberlites at all (For instance pyrope is rare in lamproites). His thesis is that the African species called the Orangeite may be the expression of Lampriote there may be true. Mitchell's book on Lamproites is instructive. A common misconception regarding diamond hunting is that the mobile-belt-craton theory and its ramifications are gospel. It does indeed seem that kimberlites with diamonds are rarer in mountainous regions and this perhaps can be explained by the higher heat and subduction regimes that raise the oxygen fugacity of the tranport melt. But kimberlites with abundant chrome garnets do exist in mountainous regions and we must remember that DeBeers first promulgated the cratonic theory as means of fooling surrounding African states into not exploring for diamonds in their countries. In fact Cratons or ancient stabilized basins are spread over enormous areas. We can see that all of China, nearly all of Canada and most of Australia and Siberia are in fact such structures. If they were not then the Cambrian Rocks could not have settled on the Archean platform in a subaqueous environment. And when we look at the positions of economic kimberlites in relation to the basins we see that many producers of good repute are near the edge of the imputed craton and not too many exist near its centre. If in fact you wanted to look in the most stable cratonic area of Canada you would come right back to Ontario and Manitoba where the crust is undoubtedly thickest and oldest. It was basin in Archean times. And you would stay away from the Grenville as there can be no diamonds where such a massive orogeny took place near its borders. Yet when we get there to this proterozoic upheaval area we find many kimberlites. Is it old enough and deep enough? Just what is this depth and age co-efficient or is it all hooey? Diamonds is where you find em? EC<:-}

To: George J. Tromp who wrote (1737)	12/6/1998 11:39:00 AM
From: E. Charters	Read Replies (1) \| Respond to of 2251

Carbonate rocks can be quite busy but kimberlites that are magnetic will contrast highly. There are however many holes in the carb rocks that are highs as they "shallow" the cover and expose more magnetic rocks. Despite this the exploration is dead easy on the islands compared to taiga. About 35% yield to VL aerial spotting. The age of most volcanic rocks in Canada has been established and the GSC probably did Lead-Lead dating on them a few years back. Also Hyder Gold may have had GSC boys in on their VI camp and they love to age date. The kimberlites may be quite young. I would estimate less than 35 million years. The Economic Geology of Canada Series by the GSC has bits on VI. It has many pete seepages and tarsands. Dark areas in the photos I have seen may be Kimberlites. The analog for that work was done on Somerset Island, the site of some of Canada's first in situ diamond discoveries by Cominco in the 70's. the first people on VI was a company led by a former Cominco boy, Ken Carter. BTW the nickel temp does not lie, that is nice to hear but what was it? 950? 1100? Was it bi-modal temp or uni-peak? 63.4% chromate Chromites are low. You want to see 68% and higher. EC<:-}