Can a small crack in a Peugeot 103 "Special Tubing" road bike frame be repaired with a MIG welder?

I have a Peugeot road bike that is from the 1980s and have noticed that there is a small crack in one of the lugs. Can this be repaired with a MIG welder. I don't know what the frame is made from, but there is a sticker that says 103 "tube special" on the frame. Can anyone help me?