RE: cornishknocker23 Jan 2021 00:03
Hi Troajan, I don't know how well you understand the cornish Lode structures (Hydrothermal vein systems).
Typically a lode down here is between 0.6m and 10m in width, which will dip from horizontal from between 40 to 70 degrees, in a locality they generally dip in the same direction and strike in the same direction. (That is as a result of way they were placed).
The lode strike can persist for several kilometres and they can extend from surface to in the region of 1200m down dip.
If you were to take a sheet of A4 paper (in portrait) and draw a line from the top left corner to the bottom right corner and call that the lode; then draw a line from the top right corner to anywhere on the bottom or left hand side of the paper (call that the drill hole) you will see it is impossible to not intercept the lode, no matter how fine your pencil line.
In reality the structure will always be there (unless some later geological fault has caused it to move), the question is the valuable mineral content of the intercept, which may be barren or may be exceptionally rich - it can vary enormously over a short distance.
The reason tge deposits formed like this is if you imagine they original rock (devonian sediments) which were in place some 250 million years ago were disturbed by the formation of the Cornubian granite batholith, wich was an igneous intrusion from below. In some areas that intrusion found a weakness that allowed the granite to push through to surface (Kit hill in this case), as it pushed through it caused tension cracks in the sediments (which were metamorphosed), radiating (in Camborne where a long ridge was formed, these cracks run parallel with the ridge) out from where the magma pushed through. Hydrothermal fluids containing the minerals then flowed into these tension cracks, as the fluid solidified, the lides were formed.
I expect a geologist would rip that description apart - the overall ore genesis in Cornwall is pretty complex, buy that is it simply.