Note. The majority of this paper is a transcription from the video of the AusIMM Webinar at the Western Australian, South West Branch on the 30th July 2020 (https://vimeo.com/464013825/1ed4a0c752). The language is thus vernacular and not geologese. This should make it more easily read and understood by the majority of readers.
Additions have been made to expand and clarify sections that were abbreviated due to time constraints in the Webinar. References quoted in the webinar, as well as background papers referenced but not quoted in the webinar, are listed in the text and in the references section at the end of the paper.
We are now going to look at a more detailed enhancement of the mines in South Africa.
The above figure (Figure 34) is African seismic tomography at 135 km depth showing detailed tomography of South Africa by Griffin et al. 2009
Figure 35. African seismic tomography at 135 km depth showing mines.
The figure (Griffin et al. 2009) shows the tomography in more detail than the broad tomography of Begg et al 2009 used for the overall study and the metals and diamond mines are plotted over this tomography. Kimberlite pipes are showing as the small grey spots. The conclusion at the end of the Griffin 2009 paper was that the diamond mines lay around the periphery of the Cratons. We will be able to do much better than that with this ultra-detail.
Figure 36. African seismic tomography at 135 km depth showing detailed structure.
The figure has only a few iterations of enhancement but I could see what I wanted to see while the grey cratonic colours were still visible. There are EW structures, ENE structures, NE structures and NNW structures. How did these relate to the mines? Generally, the less iterations one can use to see the structure the truer the image will be to the original data.
Figure 37. African seismic tomography at 135 km depth showing the detailed tomographic structure association with mines.
There is good correlation of the diamond mines with the ENE structures, in fact it is 100%. There is also a good correlation of the metal mines with all the linears. This is a much more focused exploration targeting tool then the current one targeting edges of cratons or 170 km thick crust.
If I was exploring for new diamond mines in South Africa, I would be looking at every pipe along the ENE trend (and targeting to find new ones) especially where they intersect the NW and NNW linears.
This image has been enhanced for ultra-detailed structural geology. The ring structures that can be seen are plotted. The diamond mines generally lie within smaller (100 – 300 km diameter) rings and ENE linear intersections and the metal mines sit on the rings and where rings are clustered together.
This is another excellent targeting focus for diamonds.
I will, belatedly, include the reference list so that the references in the overall paper can be accessed.
12. References
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Summary
This is a first pass into diamond exploration and other ways of targeting resources.
I was surprised at how close the correlation of the diamond and metal mines was to the linear and ring structure even though these structures are at 170 km depth.
If I was a diamond exploring company I would be pegging all the ground along the trends indicated before everyone else does 🙂
More will be revealed on the mineralisation mechanism as we proceed through the rest of the paper.
If you have enjoyed this episode of the larger paper on Africa – and more importantly find it useful – share it with like-minded colleagues. This is why I do this research – to get our often moribund thought processes working again!