SAN FRANCISCO (MarketWatch) — The details remain scant, but it doesn’t seem to matter. News overnight that the financial wizards of Europe have a plan to solve the region’s staggering debt crisis and save the euro had investors pouring into some big U.S. blue chips Thursday.

Of course the banks staged a relief rally. But the biggest gainer on the Dow was Alcoa Inc. AA, -0.34% , up 10% at $11.40 a share.

Why would an aluminum maker pop as such a hot stock on the euro-zone story?

Simple. Before the big chill of the European debt crisis, the region accounted for about a third of Alcoa’s revenue. That business has been shrinking ever since, and the company hasn’t minced words when describing the toll it’s taken on its bottom line.

When the situation might turn around was anybody’s guess, precisely the kind of uncertainty that’s been hurting so many of the companies whose raw materials have for decades flowed to European manufacturers.

This has obvious consequences. Alcoa’s stock has been pounded by weak aluminum demand, falling aluminum prices, and a third-quarter earnings report that feel far short of what Wall Street was looking for. Read about Alcoa's disappointing third quarter.

Until today, Alcoa’s share price was down 34% for the year. That’s an appalling drop for a company whose balance sheet is still solid and whose stock is trading at an attractive 12.4 price-to-earnings ratio.

But it also opens a big, fat entry point for anyone “bottom fishing” among the Dow 30. Today, with Europe stoking the market, they pounced, pouring just over $1 billion’s worth of capital into Alcoa stock.

And it’s not just Alcoa. Shares of iron-ore giant Rio Tinto PLC RIO, +0.29% were also up 10%. So were Freeport-McMoRan Copper & Gold FCX, +2.08% shares. Today, Freeport’s move was all about copper, since the gold component of the rally played out months ago. But copper futures, a proxy for manufacturing demand, are up 15% over the past week, with fully 5.8% of that bounce coming on today’s news from Europe.

The same phenomenon is carrying chemical companies higher. Dow Chemical shares DOW, +1.03% were up 9% despite a disappointing third-quarter earnings report. DuPont DD, +0.52% was up 6%.

So how much of the rally can be pinned to Europe’s pulling back from a financial abyss and how much is simply pent-up capital pouring into a beaten-down materials sector? Hard to say, since the motivation behind both is essentially the same thing: It’s a big bet on a rebound that after months of nail biting seems to have finally found a catalyst.

— Jim Jelter