noncents said:
Hi guys a very interesting read. I listened to Dr Karl on the ABC radio talk about the same theory. I just got a (silly) question why isn't there any gold found in the Illawarra, Sydney and Hunter areas? If gold came from a meteorites should it not be spread over the whole country?
Hi Noncents, unfortunately all the sydney -illawarra is sitting on mainly sedimentary rocks of marine and freshwater origin (with a few young volcanic vents popping through) that do not contain any substantive gold in concentrations you can look for. There is some gold on the western edge of these Sydney Basin rocks north of lithgow and also small quantities of gold in old river deposits trapped under younger lava flows that cap the rocks in a few isolated spots (eg. Mount Airley).
There is however lots of gold, hundreds of metres below the sydney -illawarra area in the much older Lachlan Fold Belt rocks (like at Hill-End -Bathurst) which underlie the sydney basin rocks.
The issue is alot of geology, rock forming, mountain building, volcanism and erosion has occurred over the 3 billion years since much (not all) of the gold was delivered to the planet by meteorites. Alas most gold we find relies on it being pressurised towards the surface by volcanic activity or molten mantle juices rising up through faults (that can also pick up gold on the way through gold bearing rocks in the crust).
hope this helps, RedDirtDigger