The 23-year-old, who has made 34 appearances for the U's this season, will be part of the Stags' squad which travels to Woking on Wednesday night.
Mansfield manager Paul Cox said: "When we learned that Chappy was available, we were keen to bring him here.
"He'll add a bit of everything to our midfield. He's a strong player, with great technical ability."
The former Sheffield United man had been a regular under Chris Wilder this season and started in their recent victories over Gillingham and Port Vale.