Mason punched Fielden after an altercation in the opening moments of the game, knocking the prop forward to the ground and leaving him nursing a broken nose.
At the appeal Mason claimed provocation, but the disciplinary panel felt that his response had been “disproportionate”.
"I'm really disappointed with the result," Mason said in a statement. "I honestly thought I was acting in self defence.
"In light of previous incidents (in the Tri Nations) which have gone unpunished I'm very surprised by tonight's result.
"I will now devote myself to getting fit and play as well as I can in the final. I wish my team-mates the best of luck in the coming game.
"I feel like I've let them down but I can't wait for the final."
Mason will miss the final game of the league stage against Great Britain, but will be eligible to take his place in the Tri-Nations final at Aussie Stadium.