Geology. As an old prof of mine once said "there is no such thing as a silly question and in fact what sometimes seems like a silly question is the hardest to answer."
Geological theories are always changing as we learn more. I can remember in school a student being chastized for suggesting it looked like all the continents could fit together like pieces in a jig saw puzzle. Lo and behold the theory of continental drift came along and now is accepted wisdom.
For most of the world history the planet seems to have been in a pretty temperate or even tropical state. In the high arctic in Canada, Russia etc the remains of tropical forests can be found. Even though the climate had six months of light and six months of dark it was warm enough for forests and aligators to survive in the far north.
The diavik pipe when it errupted did so in a forested area because they have found charred wood in the kimberlite a couple hundred feet down into the pipe.
Serveral of the pipes found in the NWT still have parts of their crator facies (top most layer) still intact.
Kimberlite is soft and weathers easily so the tops of the pipes and dykes weathered. Along came glaciation and picked up this material carying it "down ice" and it was left behind when the glaciers melted.
So companies sample the till looking for indicator minerals. If they find them they try to follow the trains back up ice to the source.
Fipke is reported to have followed the indicators all the way from the Mackenzie river back to Lac du gras a distance of several hundred miles. He was following the train from a diamond field we know know contains several hundred pipes.
Most indicator trains are much shorter. In theory and practise the more indicators you get the closer you are to the pipe. The trains look a little like fans and get narrower more concentrated as you get closer to the pipe. Some close to the pipe even contain kimberlite fragments, diamonds and kimberlite boulders.
Anywher along that train you might also find a diamond. A old prospector in Yellowknife Jake woolgar, who died long before the diamond rush, had found two small diamonds panning in the NWT but he would never say where he found them. I believe sooner or latter some sharp eyed individual will indeed find a 5, 10, 20 or 50 carat diamond laying on the surface or mixed in with the glacial till. Also in the right area someone may find a small pocket of placer diamonds.
The dyke at Snap did come to surface and left behind a train of indicator mineral, boulders and even a few diamonds. they dug down through a bit of overburden and from a sample found the diamonds so some may indeed be laying around in the till or have been washed into snap or surrounding creeks and streams. In fact several dykes appear in and around snap so you though of mining the lake bottom, may not be unrealistic, at some point.
I know if I were working in the area I would sure be looking closely at the little streams etc.
I recently had a talk with a belgian geo who is really up on kimberlites diamonds etc and he thinks alot more discovers will be made and that older pipes may have been altered and harder to find and that diamonds may be found in old paleo channels. Meaning really old pipes could have weather significantly and the diamonds been deposited in sands and gravels, clays and muds which have since been turned into sandstones, siltstones conglomerates etc and someday someone may find one of these to be diamond bearing. Why not. No one has really looked for them yet.
Geology always throughs us a few surprises and you never know what you are going to find untill you look.
hope that helps some.
regards Walt |
