WHILE MANEUVERING THE ENG QUIT PRODUCING POWER. THE RT WING SEPARATED AFTER COLLIDING WITH A TREE DURING THE LANDING ROLL; THEREFORE, NO DETERMINATION COULD BE MADE IF THE SUPPLY WAS CONTAMINATED. THE REMAINING FUEL SUPPLY WAS CHECKED FOR CONTAMINANTS; NONE WERE FOUND. THE ENG WAS STARTED & FOUND TO OPERATE NORMALLY. NO DETERMINATION COULD BE MADE AS TO THE REASON FOR THE LOSS OF ENG POWER.