Brazil convincingly won the World Cup battle of South America's soccer giants today, eliminating defending champion Argentina, 3-1, in Barcelona.

In the day's other match, West Germany ousted Spain, 2-1, in Group B at Madrid.

A capacity crowd of 40,000 at Barcelona's Sarria Stadium saw the Brazil-Argentina game end on a hectic and somewhat sour note. Argentina's superstar Diego Maradona was sent off by Mexican referee Mario Rubio Vasquez after a nasty foul on Brazil's Batista, who had just replaced Zico. Zico scored his team's first goal and set up the other two.

Maradona, who showed brief flashes of brilliance, appeared frustrated at his inability to penetrate the Brazilian defense and particularly to escape the watchful eye of Oscar, a talented central defender, who, for some reason, was unable to adjust to the North American Soccer League during a brief stay with the Cosmos several seasons ago.

Maradona was expelled after he retaliated for a foul Batista had committed against Juan Barbas.

Brazil will play Italy Monday to determine the semifinalist from Group C. The winner of that encounter will take on the winner of Sunday's game between the Soviet Union and Poland. If either game is tied, Brazil or Poland would advance on the basis of goal difference.

The first goal came in the 12th minute, when Brazil was awarded a free kick from 30 yards--a situation in which the Brazilians are known to be particularly dangerous.

Serginho blasted a high hard shot that grazed Argentine goalkeeper Ubaldo Fillol's finger tips and struck the crossbar with full force. The ball bounced downward, and Zico, who charged the net with Serginho, punched it in.

The rest of the first half was filled with neat little passes leading to goal-scoring opportunities on both sides, but generally the attackers were unable to get solid shots on goal. Fillol was tested by Eder in the 23rd minute, and his counterpart Waldir Perez had to make a tough save with two minutes left in the half.

In the first 10 minutes of the second half, Argentina started a flurry that created more than a little confusion in the Brazilian defense. Maradona appeared to be brought down in the penalty area, but Rubio Vasquez ignored Maradona's pleas for a penalty.

The Brazilians began to take over again and, at the 66th minute, Zico was clear in front of Fillol's goal and missed the net widely with an artistic scissors kick. A minute later Zico freed Roberto Falcao with a pass to the right, Falcao chipped a long pass over Fillol's head and Serginho was clear to head it home to make it 2-O.

Then, unlike all the European teams in the tournament this year except Poland in its last two matches, the Brazilians continued to attack, despite their lead. In the 73rd minute, Zico blasted a free kick just over the net.

Hardly a minute later, Zico set up a classic goal with a diagonal pass to Junior, who sprinted toward the goal on the left side and had only Fillol to beat to make it 3-0.

Things began to get a bit rough, and Maradona committed his red-card foul in the 86th minute.

Three minutes later, Ramon Diaz scored a goal that had nothing but statistical value. It was a nice, hard shot into the upper left hand side.

After its victory before 90,000 in Madrid's Santiago Bernabeu Stadium, West Germany now must await the result of Monday's game between Spain and England to see if it or England advances to the semifinals.

If Spain ties or beats England, West Germany would advance. If England wins by more than one goal, or scores more than two, it would qualify. If England wins, 1-0, the Germans would advance, and if the score is 2-1 for England, the semifinalist would be decided by lot.

West Germany or England will meet France, which needs only a tie, or Northern Ireland, which must win, when those teams play Sunday.

West Germany was led by the cool play of sweeper Uli Stielike, who was playing on familiar turf, since he is a star for the Real Madrid club that owns the stadium.

Stielike organized the defense, and started the play that led to the first goal, five minutes into the second half, when Pierre Littbarski rammed in a rebound of a hard shot by Karl-Heinz Foerster.

The second German goal came after two quick, short passes inside the penalty area, the last one from Littbarski, who set up Klaus Fischer alone on the left. Arconada had to leave the goal line to try to cut off the play, and Fischer hit the empty net.

Six minutes later, Jesus Zamora's header accounted for the game's final goal.