Gold prices slumped more than $100 an ounce on Friday, the biggest fall on record in dollar terms, as traders sold to cover losses, while global stocks edged up on expectations the European Central Bank will take new measures to contain the euro zone debt crisis.

Trading was volatile, capping one of the most tumultuous weeks on record for world markets as fear of a Greek default and a gloomy Federal Reserve prognosis for the U.S. economy sparked a sell-off in stocks and commodities and drove investors to the safe-haven U.S. dollar and Treasuries.

A pledge by G20 policy makers that they will calm the global financial system failed to appease investors, who are concerned that authorities are unable to respond effectively to the mounting euro zone debt crisis and sluggish growth in major world economies.

Gold slumped more than 6 percent at one point -- its biggest drop since the financial crisis in 2008 -- to hit its lowest since early August as a slide turned into a free-fall, with weeks of volatility and talk of hedge fund liquidation wrecking its safe-haven status.

The bull case for gold is on pause for the near term, said Adam Klopfenstein, senior market strategist for precious metals at MF Global in Chicago.

In the near-term, the flight-to-quality interest in owning gold is also out of the window as people are not interested in buying it even in the face of fears in the economy. Until it stabilizes, I'm staying out of this market.

Spot gold was last at $1,649 an ounce, after falling to a session low under $1,628. At $127 an ounce, the intraday move was the biggest on record in dollar terms.

U.S. stocks ended higher after seesawing between gains and losses, stopping the bleeding after a disastrous four days of selling marred by severe anxiety.

Comments from European Central Bank Governing Council member Ewald Nowotny, who said it might be advisable for the central bank to add more liquidity to European banks helped lift sentiment.

The Dow Jones industrial average ended up 37.65 points, or 0.35 percent, at 10,771.48. The Standard & Poor's 500 Index was up 6.87 points, or 0.61 percent, at 1,136.43. The Nasdaq Composite Index was up 27.56 points, or 1.12 percent, at 2,483.23.

Global stocks as measured by the MSCI All-Country index were up 0.2 percent, after hitting their lowest level since July 2010 at 274.20.

The index is now in bear market territory -- defined as a fall of 20 percent or more from the peak -- having tumbled more than 22 percent from its 2011 high in May.

Financial markets are sick and tired of the authorities in Europe and in the U.S. twiddling their thumbs and not doing substantive things to solve this crisis of the global economy, said Barton Biggs, managing partner at New York-based Traxis Partners.

The FTSEurofirst 300 index ended up 0.8 percent. Emerging markets stocks slid 1.6 percent.

COMMODITIES ROUT

Liquidity comments from ECB officials and speculation the central bank may cut rates helped sentiment initially, but uncertainty about Greece remained.

Greece denied reports that one option in its debt crisis would be an orderly default with a 50 percent haircut, while Deutsche Bank warned that European banks' write-downs on Greek bonds could exceed 25 percent.

Metals prices plunged across the board. Silver prices posted their biggest drop since 2006. Spot silver was down 15 percent and trading below $35.76 an ounce after hitting a session low of $29.77.

Copper hit $7,115.75, its lowest since August 2010. It was its sharpest weekly decline in nearly three years for the economically sensitive red metal.

U.S. crude fell 66 cents to settle at $79.85 a barrel. London Brent crude fell $1.52 to settle at $103.97.

The euro rose 0.4 percent to $1.3515, rebounding from an eight-month low. The dollar rose 0.5 percent to 76.66 yen and was on track for its best month since May 2010 against a basket of currencies.

U.S. Treasuries prices slipped after a huge rally this week.

Benchmark U.S. 10-year notes were down 1-2/32 in price, with yields rising to 1.84 percent. Prices of 30-year bonds were down 2-1/32, yielding 2.90 percent.

(Additional reporting by Ryan Vlastelica, Steven C. Johnson and Barani Krishnan in New York and Harpreet Bhal in London; Editing by Andrew Hay)

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