Jan 17 (Reuters) - Glencore approached Rio Tinto late last year about combining the two big copper producers but the discussions are no longer active, a person familiar with the matter said.

The talks between Rio, the world's No. 2 miner, and Glencore, one of the world's biggest producers of coal and base metals, were brief and did not go anywhere, the person added.

Bloomberg News reported on Thursday that the two were in early-stage merger talks.

A merger between the firms has the potential to be the largest ever in the mining industry. They have a combined market value of around $158 billion, surpassing BHP's  $126 billion.

Rio and Glencore declined to comment. Global miners have been sizing each other up as they look at ways to bolster their position in metals such as copper that are set to be in high demand as industries shift to cleaner forms of energy.

That was the rationale behind BHP's $49 billion bid for smaller peer Anglo American last year but which failed due to issues with the deal's structure.

Portfolio manager Ben Cleary at Tribeca Investment Partners, which has its largest position in Glencore, said that if Rio was interested, it would have to pay a significant premium.

Glencore, which was last trading at roughly 3.5 pounds per share, is expected to reward shareholders with capital returns this year following a $34 billion merger of its Viterra unit with Bunge (BG.N).