The Australian share market has rallied, led by the big miners, ahead of the central bank’s decision on interest rates.

The benchmark S&P/ASX200 index was up 50.6 points, or 0.81 per cent, to 6,334.3 points at 1200 AEST on Tuesday, while the broader All Ordinaries was up 49.3 points, or 0.77 per cent, to 6,419.2.

Every sector of the ASX was in positive territory at midday as the heavyweight materials segment led gains by adding 1.60 per cent.

BHP was up 1.55 per cent to $37.37, Rio Tinto was up 2.63 per cent to $96.41 and Fortescue Metals was up 6.29 per cent to $7.60.

The big four banks all advanced, with ANZ up 1.11 per cent to $27.855, Commonwealth up 0.61 per cent to $75.40, NAB up 0.83 per cent to $26.135 and Westpac up 1.09 per cent to $27.405.

GrainCorp was down 6.68 per cent to $8.175 after Long-Term Asset Partners withdrew its takeover offer for the bulk grain handler.

Actinogen Medical crashed 68.75 per cent to 1.5 cents after the Sydney biotech company said a clinical trial revealed its drug hadn’t worked to treat Alzheimer’s disease.

The Reserve Bank of Australia will announce at 1430 AEST whether it will hold the cash rate at 1.5 per cent or cut to a new record low.

The Aussie dollar is buying 70.03 US cents, from 69.91 US cents on Monday.