1. Stir together first 5 ingredients in a medium bowl; set aside 2 tablespoons. Add tuna to remaining marinade, stirring gently to mix. Cover tuna mixture, and refrigerate 30 minutes to 1 hour, stirring once or twice.
2. Soak bamboo skewers in cold water at least 30 minutes.
3. Preheat broiler, and place top rack about 4 inches below element. Thread tuna and mango cubes onto skewers. Arrange skewers on a rimmed baking sheet, and brush with marinade.
4. Broil 2 minutes. Turn skewers, and broil 1 to 2 more minutes or until tuna reaches medium, with just a bit of pink remaining at the centers. Arrange skewers on plates; drizzle evenly with reserved 2 tablespoons marinade.