NEW YORK, Sept 9 (Reuters) - Citigroup's ( C/PN )

investment banking fees are expected to jump 20% in the third

quarter from a year earlier, Chief Financial Officer Mark Mason

told investors at a conference in New York on Monday.

The gains are being driven by a good pickup in activity

across debt capital markets and mergers and acquisitions, Mason

said.

Meanwhile, markets revenue is likely to drop about 4%,

he added.