[daemin]

I'd say a lot of the growth has been by exporting dirt and food to China and other Asian countries. This made Australia resistant to the GFC crashes because our raw materials were in great demand. It was also regardless of immigration as other countries with similar levels of immigration did not have the same economic success.

[vacri]

Mining is only 7-8% of our economy. We survived both the GFC and the recent years of mining downturn. Mining isn't a small part of it, but it's not really the key player in our economy. Agriculture is much bigger, but still, the reason why we import so many humans[1] is to keep our economy growing. Immigration isn't the only thing that can affect an economy, but with an ageing population, bringing in new youthful blood helps keep the workforce growing.

[1] The only large Western nations with higher immigration rates are Spain and, surprisingly, Norway.