The Australian share market closed at its highest level since late April as traders reacted positively to the potential blocking of BHP Billiton's $40 billion Canadian fertiliser bid. The benchmark S&P/ASX200 index was up 22.7 points, or 0.48 per cent, at 4,745.3, while the broader All Ordinaries index had gained 23.8 points, or 0.50 per cent, to 4,817.6 points. It was the all Ordds highest close since April 30. On the ASX24, the December share price index futures contract was up 31 points at 4,758, with 30,106 contracts traded.

The miner said it would keep working with the Canadian government, after its $A39.87 billion for fertiliser maker Potash Corporation was given an initial thumbs down by that government. Shares in BHP Billiton closed up $1.09, or 2.56 per cent, at $43.72. Fellow big miners were mixed. Rio Tinto fell 19 cents to $83.20, while Fortescue Metals was up 20 cents, or 3.08 per cent, at $6.69.

The four big banks were mixed. ANZ was the second worst performer on the S&P/ASX50, down 86 cents, or 3.41 per cent, at $24.34 after going ex-dividend. Commonwealth Bank was also lower, down 76 cents at $49.14 and Westpac was down seven cents at $23.35, but National Australia Bank was 10 cents higher at $26.00.

Oil Search was the second best performer on the S&P/ASX50, up 19 cents, or 2.93 per cent, at $6.68, Woodside was 81 cents higher, or 1.84 per cent, at $44.89 and Santos gained 11 cents to $12.85. Qantas recorded its highest volume since February 18 this year, with over 62 million changing hands after one of the airline's Airbus A380's experienced engine problems and had to return to Singapore's Changi Airport. Qantas closed up two cents at $2.89. David Jones finished down 12 cents, or 2.56 per cent, at $4.57, JB Hi-Fi dropped 43 cents to $19.19, Myer Holdings fell four cents at $3.81 and Harvey Norman was three cents lower at $3.14.

In market news on Thursday, global media giant News Corporation maintained earnings guidance for the current year after posting a hefty jump in first quarter profit. News Corp ended up two cents at $16.54 while its non-voting scrip had risen 67 cents, or 1.09 per cent, to $14.90. Boral finished flat at $4.36 after saying it had a bumpy start to the financial year and forecast a flat first before an improvement in the following six months.

Leighton Holdings was down 25 cents at $32.85 after the construction company said its first quarter profit had been hit problems associated with the construction of the the Brisbane Airport Link project. The spot price of gold in Sydney was $1,354.50 per fine ounce, down 15 cents from Wednesday's local close of $1,354.65. Gold miner Newcrest Mining was up 57 cents, or 1.41 per cent, at $40.96.

The top-traded stock by volume was Cellmid Ltd, with 397.59 million shares worth $32.09 million changing hands. Cellmid shares were up 1.1 cents, or 18.33 per cent, at 7.1 cents. The medical biotech company announced this week that it had completed the development of a blood test for early cancer diagnosis. Preliminary national turnover was 2.72 billion shares worth $6.53 billion, with 628 stocks up, 490 down and 365 unchanged.

The Australian dollar rallied back above parity with the U.S. dollar and traded at its highest level since the currency was floated in 1983 on Thursday as the U.S. Federal Reserve outlined a second round of quantitative easing. Australian bonds on the short end of the curve were slightly lower. Buying in riskier assets including the Australian dollar was robust as the Federal Reserve disclosed a US$600 billion asset buying plan, known as quantitative easing, to inject life into an anemic U.S. economy.

The Fed buying was even seen by some as a relief the central bank didn't pursue a more aggressive asset buying plan. For the Australian dollar, the Fed move immediately lifted the currency back above parity with the U.S. dollar for the first time this week, where it remained for much of the day. Even as local data on retail sales and the country's trade surplus came in below analysts' expectations, the data could do little to stunt the Australian dollar's ascent.

As the week points to a close, traders said even Friday's release of the Reserve Bank of Australia's November meeting minutes would be unlikely to make big waves with the currency. On Tuesday, the RBA surprised the market by raising its key cash rate 25 basis points to 4.75% after having been on hold for the past six months. The Australian dollar traded at $1.0049, up from $0.9974 late Wednesday. Against the Japanese yen, the currency traded at 81.205, up from 80.455.