JOHANNESBURG (Reuters) - South Africa's Standard Bank said on Friday it would appeal an arbitration ruling to refund at least $60 million worth of shares to a union pension fund.

"Standard Bank will, within a week, appeal the whole of the award of the arbitrator," Africa's largest lender said in a statement, adding the arbitrator had failed to take into consideration several mitigating issues.

An arbitrator ordered the bank this month to pay at least 528 million rand ($60 million) worth of shares to a pension fund belonging to the South African Commercial, Catering and Allied Workers Union.

The case, which had previously been in litigation in a high court, dates back to a 2002 deal between the bank and the fund in which the fund lent Standard Bank shares and was later repaid.

The arbitrator ruled the deal should have never happened and ordered Standard Bank to surrender shares in mobile firm MTN and media company Naspers worth about 528 million rand, based on this week's prices.

(Reporting by David Dolan; Editing by Ed Cropley)