The recent uptick in mining mergers and acquisitions (M&A) is masking the slowdown in greenfield exploration projects. Companies are increasingly relying on acquisitions rather than the expensive and risky process of discovering new deposits.

After making a new all-time high in May, copper has declined and stepped down from the headlines, leaving gold in the top spot. Despite copper's price decline, its looming shortages continue to trouble analysts, who project significant discrepancies between supply and demand in coming years.

BHP Group Ltd.'s (NYSE:BHP) Oak Dam project in Australia, discovered in 2018, presents one of the...