The pair came to blows when they came off the field at half-time during Wednesday's 2-0 defeat at Gremio and were shown the red card, leaving Palmeiras two men short for the entire second half.
"The two players will never again wear the Palmeiras shirt," club vice-president Gilberto Cipullo told reporters.
Striker Obina and defender Mauricio argued over Gremio's opening goal, scored in first half stoppage time by central defender Rafael Marques after keeper Marcos parried a shot from Argentine striker Maxi Lopez.
The pair argued as they walked off after the halftime whistle at the Olympic stadium in Porto Alegre, then exchanged punches and had to be pulled apart by other players.
Lopez scored Gremio's second in the 70th minute.
Palmeiras, who had spent 19 consecutive rounds of the Brazilian championships in first place, have now won only one of their last nine matches and are in third place.
They are three points behind leaders Sao Paulo, who have a game in hand, and visit lowly Botafogo on Sunday while second-placed Flamengo host Goias.
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