The hot spot is stationary - there is another hot-spot offshore east of it (formed Lord Howe Island). Australia broke away from Antarctica and has been moving northwards through time, but the hot spot source is stationary (it is below the moving and overlying lithosphere). Imagine a conveyor belt moving over a fire. Volcanic rocks keep punching through to the Australian surface (eg the Warrumbungles, the Macedon Ranges). Sapphires, zircons and possibly the diamonds have come up with these volcanic rocks. However it is possible that the diamonds have a different source to the sapphires and zircons, if the subduction model is correct (subduction diamonds have a different age to other mantle diamonds, the latter all being around three billion years, and are associated with eclogite, ocean floor basalt subjected to high pressure). The model I mentioned is almost certainly correct for the sapphires and zircons (which can be traced back to their individual volcanic sources - at Daylesford large zircons occur embedded in the lava). The hot spots are currently under Bass Strait and further east (well, more correctly that it the part of the Australian crust currently moving over the hot spot). Volcanoes in the western district of Victoria and around Mt Gambier in adjoining South Australia are as little as a few thousand years old, and their eruption is recorded in aboriginal "legend" (other such "legends" such as meteorite swarms hitting central Australia and Port Phillip Bay being dry with the Yarra flowing out the Heads have also proved to be true, so could be considered verbal history not legend). Molten magma is present just east of Flinders Island at present (detected because seismic waves during earthquakes cannot pass through a fluid). Future eruptions around Bass Strait can be expected.Chimpy said:G'day
this is an image of the 'subduction model' thought to create our diamonds (model for the Bingara region)
https://www.prospectingaustralia.co...s/555/1384768832_lge_subduction_dia_model.jpg
Nobody is 100% sure though because no primary diatremes or pipes have been located to date. I did hear a theory that there is a thermal hot-spot that the east side of NSW has been moving over as the continental plate drifts north. I don't know if there is solid evidence of this but the map of occurences does suggest this could be a possibility if you combine it with the subduction theory of formation.
A thorough search of the DIGS database will turn up plenty of interesting reports and info.
I've entertained the pipedream (literally) of hunting down a 'diamond pipe', as have many before me, and done a fair bit of research but thats as far as I've got. The mystery continues......
Cheers
Chimpy
If the subduction model for Australian diamonds is correct, their present wide distribution may have been accentuated by their transport for long distances away from their source areas by glacier ice during Permian times (e.g. those around Beechworth are spatially associated with glacial diamictite rocks, as in some other locations).
