Bates had joined Aberdeen from Hamburg last summer after a spell in Belgium with Cercle Brugge.

The defender, who has four Scotland caps, began his career with Rangers before joining Hamburg.

Danny Buijs' Mechelen currently sit 10th in the Belgian top flight after finishing eight last season.

Aberdeen manager Jim Goodwin had earlier stated that he was open to Bates and striker Christian Ramirez finding new clubs and suggested that it was time for 22-year-old forward Connor McLennan to move on in pursuit of more regular first-time starts.

However, Goodwin played down the possibility of United States international Ramirez joining Heart of Midlothian following newspaper reports amid the Edinburgh club's hunt for a replacement following Liam Boyce's long-term injury.

"I can't see us loaning a player to one of our rivals," he added. "And, as of this moment in time, I'm not aware that Hearts have even made contact."