The price of gold is tied to the value of the dollar, so when the dollar of the value goes down people put some of their investments in gold to hedge their portfolio.
I think that's simply an obvious result of supply/demand. Investors know that when the value of the dollar drops, people will invest in gold...so, as the value of the dollar begins to drop, the price of gold goes up.
Kinda like the price of gas going up around Memorial Day..it's not because production costs go up; rather it's because people typically will drive more during the summer.