The gritty legions of the United Mine Workers of America yesterday voted overwhelmingly to put their future in the hands of young, pin-striped lawyer Rich Trumka, ousting their current president, Sam Church Jr.

With 651 of 868 locals reporting, Trumka had 72,896 votes to Church's 34,399 in the unofficial count.

Trumka's lead in the larger locals of Appalachia seemed to stun Church supporters. The 33-year-old challenger, who left the mines after 3 1/2 years to become a union lawyer, led even in Church's home district in Virginia.

"I look forward to having someone explain what happened," Tack Cornelius, Church's spokesman, told a gloomy gathering at the Charleston, W.Va., hotel where supporters had gathered. "Have they bought the three-piece suit versus the overalls? Is it the layoffs? If we had lost 55 to 45 percent, I would have said it was the layoffs, but this . . . . "

"We kept in close touch with the rank and file," said Joe Corcoran, spokesman for Trumka at his Uniontown, Pa., headquarters. "I'm thrilled to death."

Earlier in the day, after he voted at a mine bathhouse near Appalachia, Va., Church, 46, responded to a question about what he would do if he lost, saying: "Get my tools out and keep Westmoreland's jump running for them." He was using miner's slang for a company dig.

The candidates had cast the choice as one of Church's moderation or Trumka's militancy, and Church's experience as a man of the people who worked his way up through the union ranks, or Trumka's youth and sophistication.

As the campaign ended, Trumka had told supporters that yesterday would be "the day the rank and file tells the world, and Sam Church, that the UMW will rise again. If it deals with coal, you'll deal with the UMWA or you won't deal."

Trumka presented himself as a man who could cope with the changed world of the miner, with its new technology and its complicated paper deals, and who could stand up to the mine operators more aggressively than Church had.

Church, a former mine electrician from Virginia, assumed the UMW leadership when Arnold Miller resigned in 1979 because of poor health. This was his first run for election to a full five-year term.

Church said yesterday that his reelection would be "a good, strong message that the miners want to work, they want stability, they want to provide a decent living for their families."

Church's tenure brought the miners a fat contract with increases of more than 37 percent in wages and benefits over 40 months. Some miners now earn more than $100 a day for the first time in industry history.

But more than 35,000 miners are laid off, and the UMW's dominance has faded as new, nonunion mines have opened in the West.

Some 220,000 miners, including an estimated 60,000 pensioners, were eligible to vote, most of them in West Virginia, Pennsylvania, Illinois and Kentucky. Trumka's base of support was thought to be among the younger miners, while Church was counting on the pensioners' vote.

The year-long campaign was a bitter one, with name-calling and allegations of shady activity flying back and forth.

As he voted in his home town of Nemacolin, Pa., early yesterday, Trumka repeated his complaint that Church had tried to smear him.

Church, or his supporters, have made references to Trumka's attractiveness to leftists.

A bachelor who lives with his parents, Trumka is a third-generation miner who left the mines to attend law school at Villanova University.

Church, by contrast, is a tobacco-chewing, barrel-chested, bearded man known as a brawler during his early days as a union official. He once turned to singing in an effort to inform Americans of the advantages of coal over oil, recording a number titled "Black Gold." graphics 1/photo: RICH TRUMKA ...lead seems to stun foes graphics 2/photo: UPI Miner looks over ballot before voting at Pawnee, Ill.