Lundin Mining Corp. agreed to buy a controlling stake in the Candelaria copper mining complex in Chile from Freeport-McMoRan Inc. for at least $1.8 billion to gain a foothold in the world’s largest supplier of the metal.

Lundin, a Canadian base-metals producer, plans to finance the acquisition with $1 billion in new senior secured debt and the sale of about $600 million of shares, the Toronto-based company said yesterday in a statement. It also agreed to a so- called streaming deal with royalty company Franco-Nevada Corp.

Candelaria would be Lundin’s biggest acquisition and double its copper production as the company snaps up unwanted assets put up for sale by the world’s biggest producers. Miners including Freeport and Rio Tinto Group, which last year sold a Michigan nickel and copper mine to Lundin for $315 million, have sought to reduce debt and focus on their most profitable operations.

The transaction adds “operational and geographic diversification,” Lundin Chief Executive Officer Paul Conibear said in the statement. The company, which started production last month from the Eagle mine in Michigan, also operates in Portugal, Sweden and Spain and has a minority interest in Freeport’s Tenke Fungurume mine in the Democratic Republic of Congo.

Freeport, the world’s largest publicly traded copper producer, is seeking to reduce debt that jumped almost sixfold last year to more than $20 billion following its acquisitions of two oil and natural gas producers. The Phoenix-based company plans to cut debt to $12 billion by 2016 and may also sell $4 billion to $5 billion of onshore energy assets, executives said in July.

Lundin fell 4 percent to C$5.12 at 9:46 a.m. in Toronto. Freeport declined 0.7 percent to $32.26 in New York.

In the deal announced yesterday, Freeport agreed to sell Lundin its 80 percent stake of the Candelaria mine and nearby Ojos del Salado operation. The rest is owned by Japan’s Sumitomo Corp. and Sumitomo Metal Mining Co., which together have chosen to keep their holdings, Lundinsaid. The mines produced 422 million pounds of copper and 101,000 ounces of gold in 2013, Phoenix-based Freeport said in a February filing.

Its after-tax net proceeds from the sale will be about $1.5 billion, Freeport said in a separate statement. Lundin also agreed to pay as much as $200 million more for Candelaria, calculated on 5 percent of net revenue in any annual period in the next five years, if the copper price moves above $4 a pound, the companies said.

Copper futures fell 0.3 percent to $3.0275 a pound at 9:51 a.m. on the Comex in New York. The price has declined 7.1 percent in the past three months on concerns about weakening growth from Europe to China, the biggest user of the metal used in pipes and wires.

In the streaming deal, Lundin will get $648 million upfront from Franco-Nevada, which will buy 68 percent of gold and silver production at a discount from Candelaria up to a certain level, after which it will be entitled to 40 percent of the metals.

Lundin has signed an agreement with GMP Securities and BMO Capital Markets to lead a syndicate of underwriters in a so- called bought-deal financing.

Lundin said it was advised on the deal by Bank of America Corp. and law firms Cassels Brock & Blackwell LLP, Bofill Mir & Alvarez Jana and Paul Weiss, Rifkind, Wharton & Garrison LLP.