I don't know what caused the dumping of all metals like you said, but gold is not just a metal. It is a safe haven and the drop in gold is just profit taking in the market after peaking as well as the impact of Trump's tax delay. These types of deals would not be large enough to impact gold prices.
the main underlying cost of mineral mining is FUEL.. so if fuel prices are dropping to a new standard. then miners can mine more profitably and be pushed by markets to sell lower, which causes the markets to drop