There is analysis on this issue in a box in the recently published . It is  Statement on Monetary Policy  worth keeping in mind the simple point that maintaining the level of demand around current levels http://www.rba.gov.au/speeches/2017/sp-dg-2017-11-13.html  4/13  13/11/2017  Business Investment in Australia | Speeches | RBA  will support prices if there is no material change in supply.
If demand declines then prices will fall, but, if it grows, then prices are likely to rise again. Following the significant addition to productive capacity from these large projects over the past decade, there has been a notable lack of exploration spending in recent years. This means there is not much prospect of any material increase in investment spending in the period ahead.