* FTSEurofirst 300 up 1.1 percent
* Euro STOXX 50 back above key retracement level
* Greek stocks dragged by credit downgrade fears
* For up-to-the-minute market news, click on
By Blaise Robinson
PARIS, Dec 20 (Reuters) - European stocks were 1.1 percent higher in seasonally quiet trade early on Monday afternoon, with a key index hitting a two-year high led by mining shares on the back of buoyant metal prices.
At 1230 GMT, the FTSEurofirst 300 index of top European shares was up 1.1 percent at 1,138.69 points, a level not seen since Sept. 22, 2008 -- a few days after the collapse of Wall Street firm Lehman Brothers.
Heavyweight metal and mining stocks led the rally on Monday, with Antofagasta up 1.6 percent and ArcelorMittal up 1.2 percent.
The STOXX basic resources index, which was up 1.2 percent on Monday, has gained 26 percent so far in 2010.
The euro zone's blue-chip Euro STOXX 50 index was up 1.4 percent at 2,862.33, to move above the 38.2 percent Fibonacci retracement of its drop to a 2009 low from a 2007 high. Next key resistance was around 2,867, the high hit a week ago.
"December's rally is almost done and the market is somewhat overbought on the short term but it does not mean the bullish trend is over," said Vincent Ganne, technical analyst at IG Markets, in Paris.
"The euro is lower today versus the dollar, but the chart shows it is pretty neutral at this point, so no big impact on European equities."
The euro struggled against the dollar on Monday following a meeting of European leaders at the end of which there were no further aggressive measures to tackle the euro zone debt crisis. The euro managed to stay above its 200-day moving average, a positive signal.
Over the past six months, the euro and the Euro STOXX 50 have had a strong positive correlation.
GREEK STOCKS' DISMAL YEAR
Greek stocks bucked the trend, with Alpha Bank down 3.4 percent and National Bank down 4.3 percent, hit by fears of a rating downgrade on the country's debt, traders said. Greece's ATG benchmark index has lost 34 percent so far this year, while the country's banking index has roughly halved.
Around Europe, Britain's FTSE 100 index was up 0.7 percent, Germany's DAX index up 1.2 percent, and France's CAC 40 up 1.2 percent.
"The market is nicely climbing, and investment themes such as exposure to emerging markets are still intact going into the next year," said David Thebault, head of quantitative sales trading, at Global Equities, in Paris.
"But it will certainly remain a trader's market, highly tactical, with a wide trading range that will offer good buying opportunities on the dips." (Additional reporting by Ingrid Melander in Athens; Editing by Dan Lalor)