Commodities trader Glencore is in talks to buy mining group Xstrata in an all-share transaction that could create a combined group worth more than 50 billion pounds ($79 billion), shaking up the industry with its biggest deal to date.

Glencore, the world's largest diversified commodities trader, already owns 34 percent of Xstrata and a tie-up between the two -- a deal which would trump Rio Tinto's $38 billion acquisition of Alcan in 2007 -- has long been expected, as Glencore aims to add more mines to its trading clout