Mining firm Freeport McMoRan Copper&Gold Inc FCX-14.09%has unveiled fresh plans to wade into the energy sector by buying McMorRan Exploration Company MMR+79.92%and Plains Exploration&Production Co.PXP+25.41%in two deals valued at a combined USD 20 billion.Shares of McMoRan Exploration jumped 75%while Plains Exploration vaulted by 23%.Freeport shares fell 16%.

With US production on the rise and energy firms plunking down billions for energy assets,Phoenix based Freeport McMoRan Copper&Gold is wading back into the space after spinning off McMoRan Exploration Company in 1994.

Freeport McMoRan said that the combined company is expected to be a premier US based natural resource company with an industry leading global portfolio of mineral assets,significant oil and gas resources and a growing production profile.

In the larger of the two deals,Freeport-McMoRan Copper&Gold will buy Plains Exploration for about USD 6.9 billion or USD 50 per share.That's a premium of 39%over its closing price.

Its purchase price for McMoRan Exploration Company is USD 2.1 billion net of 36%of the company's interests it currently owns with Plains Exploration.The deal includes USD 14.75 per share in cash and 1.5 units of a royalty trust which will hold a 5%interest in future production of the smaller firm.The cash price amounts to a premium of 74%over McMoRan's closing price.