Quite simply we were arguing about whether or not GCR has lens size potential. Red was saying they could be on to either a cluster of bodies as Kambalda types often are, or a larger body. The Kambalda are a group of somewhat similar komatiite-rock related ore bodies, (a dark ultra mafic peridotite rock that often, otherwise to the Kambalda association, contains nickel) of which the prototypes were found in Australia.
The Aussie deposits are very large and very rich, and often, somewhat differently to the Timmins deposits have pillow-selvage mineralization. They do however occur in one million to 2.5 million ton pods as parts of a cluster.
The Aussie experience was to find them blind, as they may express only a slight IP geophysical signature. They may have no surface expression. Buried flows are common here too, but we do little stratigraphic type drilling in these environments. No penetrative or saturation prospecting has been done in the Timmins camp to elucidate the best economics of the Kambalda model. I reject a pure Kambalda model as the Kambalda assumes a whole series of feeder magma sources, whilst is appears that this in Timmins mineralization is hot water related.
So far the Timmins lenses are small, being found mostly now by mining and drilling to be about 250,000 perhaps 500,000 tons. This may be because Ontario exploration for these bodies has been driven by small enterprise that has not chosen to do any deep drilling or delineation work of note to really outline the size of the bodies.
If we extrapolate the Redstone to depth of 6,000 feet, we could say it may have a lens size of perhaps 2 million tons. I don't know if it goes down however, or if any of them do in that area. Normally cu-ni lenses go down, as the Raglan does, which is also Kambalda type and as do the Sudbury deposits and the Lynn Lake group which have not been classified in modern terms.
One reason people may not have exploited that idea of depth in Timmins, was because of the model. If they assumed that they were (smal) segregation deposits they would figure they were not extensive down dip necessarily, or repeating along strike also.
Most peridotite deposits that are at the base of what is assumed an intrusive, seem to be cut off by the rock geometry.. in other words, the accumulate at the bottom of a flow or intrusion and segregate out. This limits the exploration model severely regionally. But in fact segregation type deposits are usually larger (50 mill to 800,000,000 tons) and low grade. Not these.
The model that is preferred for exploration is to drill at basins or embayments of the contact, as if one were drilling at a Sudbury type, and along strike, at varying depths and not necessarily at conductors. (Inco did not use EM for years because of the lack of correlation with many Sudbury or deposits and its lack of deep penetration where needed..)
The contact could form really subtle mag highs occasionally that are not that conductive but could be rich in mineral from 300 to 1800 feet in depth. When BHP found the Kambalda groups they were willing to do strat drilling to good depths and bang in 400 or more holes along the contacts when there were neither surface expression or EM signatures. Our companies do not have the pockets for this type of exploration so have found few blind deposits of this nature. When you go worldwide that is what you find. The buried porphyry deposits are almost exclusively the province of the BP's, and BHP's.. not even Barrick does this kind of drilling..
Mag may not work well as these bodies, unlike the Sudbury deposits are not pyrrhotite related. When you figure that a 2000 feet deep mag high for such a buried deposit would be about 15 gamma and from 4000 to 6000 feet across, AND, the rock itself is varyingly magnetic, and varying geometry and is a mag high, such deep explo is not easy. Looking at EM dots from aerial may prove very frustrating. The along-strike barren sulfide iron formation may cause confusion too. Strata drilling and down hole might be productive. Turam may be good too, as it finds very weak narrow conductors at great depth.
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