(Recasts with more investor comment, gold sector context; adds closing share prices)
By Nicole Mordant and Susan Taylor
VANCOUVER/TORONTO, July 23 (Reuters) - North American mining stocks slumped on Thursday, stripping two global producers of hundreds of millions of dollars in value, as market-beating results failed to appease investors fed up with bloated debt and hefty capital commitments.
The selloff, led by Freeport-McMoRan and Teck Resources, set the stage for a rough reporting season, as miners trudge through the fourth year of a commodity downturn.
Investors must scrutinize mining stocks and their debt loads, said Darren Lekkerkerker, co-manager of the Fidelity Global Natural Resources Fund, which has only about 4 percent of its investments in mining.
"You need to really be careful about owning those stocks, because as the commodity price comes down, when they have a lot of leverage, cash flow is really going to come down too," said Lekkerkerker.
"No one wants to own stocks where they may need to do an equity issue in order to shore up the balance sheet."
The stock of U.S.-based diversified miner and energy producer Freeport closed down 9 percent at $13.64, while Teck fell 4.6 percent to C$9.93. Both slid to six-year lows earlier, slashing $1.8 billion in market value from Freeport and C$600 million ($460 million) from Teck.
Freeport said Thursday its debt rose 3 percent in the June quarter.
"With a debt load of $20.9 billion and a market cap of $15.7 billion, it's out of line," said Maison Placements Canada Chief Executive John Ing.
Freeport's stock slide reflects "the lack of any plan to really de-lever the balance sheet in any significant way," said BB&T Capital Markets analyst Garrett Nelson.
On Monday, shares of Barrick Gold, the most levered North American gold producer, plunged 16 percent when bullion fell to five-year lows.
The most significant change for the gold sector over the past four years is climbing debt levels at North American producers, RBC Capital Markets analyst Stephen Walker said in a note.
Large gold producers hold $19 billion in debt, he estimated, equal to 61 percent of their combined market value.
Despite Teck's better-than-expected quarterly profits, investors worry about the Canadian miner's C$2.9 billion contribution to the Fort Hills oil sands project and a possible writedown of its coal assets due to weak prices, Haywood Securities analyst Kerry Smith said.
There are also concerns that Teck's credit rating could fall below investment grade.
On Thursday, copper dropped to new two-week lows of $5,267.50 a tonne and gold hit new five-year lows of $1,086 an ounce.
$1 = 1.3005 Canadian dollars Reporting by Nicole Mordant and Susan Taylor; Editing by Richard Chang