The Brown Blast Shield is found in Metroid Prime Hunters, only encountered once in Celestial Archives' Meditation Room. It requires a single Missile to unlock, and then becomes a normal Door. This door is the equivalent of Red Hatches in other Metroid games, albeit brown in color of course (the Red Blast Shield in Hunters is opened with the Imperialist). Why there is only one such door in the entire game is unknown.
"Analysis indicates the Blast Shield is impervious to most weapons. A MISSILE may damage it."