Large gold producers are coming under increasing pressure to buy copper assets simply to boost their gold reserves, the CEO and founder of of Metals Economics Group said Wednesday.

It's a geologic fact of life, said Michael Chender, in London to address this week's Mines and Money London 2011 conference.

Large gold companies have grown themselves into a tight corner. They have to replace a very substantial amount of reserves and that becomes more and more challenging over time. So if you look at gold resources that are out there, a lot of the larger ones include copper and in some cases a substantial amount of copper.

Chender pointed to the $7.69 billion acquisition earlier this year by Barrick Gold Corp. of Equinox Minerals Ltd., which operates mines in copper-rich Zambia, among other sites, as an example of the trend.

In its second-quarter 2011 report Barrick noted the link between copper and gold, saying its Equinox acquisition is adding two quality copper mines and increasing our leverage to strong copper prices while maintaining our gold exposure.

Chender said Latin America has a lot of deposits of gold nested within copper deposits but those kinds of deposits are all over the world.