Arizona copper workers, who agreed to major cuts in pay and benefits in 1986, will receive more than $10.4 million in fourth-quarter bonuses pegged to the price of copper, a union official said yesterday.

Edgar Ball, chairman of the National Nonferrous Coordinated Bargaining Conference and international secretary of the United Steelworkers of America, said that full-time workers at Magma, formerly Newmont Mining, will receive up to $2,600 in bonuses for the fourth quarter and that workers at Inspiration Resources will receive as much as $2,342.60.

In 1986, copper workers agreed to major changes in their contracts in the wake of several years of recession in the industry and following a nasty strike at the Phelps Dodge mine in Morenci, Ariz., that resulted in union workers being permanently replaced. At Magma and Inspiration, workers took cuts in pay and benefits equal to about 15 percent of compensation.

Since then, however, copper prices have more than doubled as a result of gradually rising demand and tighter supplies. At the same time, labor savings, new investment and cutbacks in marginal capacity have made the industry more profitable.

In the third quarter of 1987, workers received relatively small bonuses, ranging from $312 to $426.

In the fourth quarter, the average New York Commodity Exchange price for copper was 78.2 cents per pound, triggering bonuses of 82 cents per hour for employees of Inspiration and 60 cents for Magma workers.

The workers concessions were "really an investment in the future of their industry in the form of price-related bonuses" and that investment is "now beginning to bear fruit," Ball said yesterday.

Union workers at Asarco, another major copper producer, received automatic, across-the-board hourly wage increases in 1987 and 1988 to offset the concessions made in the 1986 contract.

Workers at Kennecott Corp. in Utah granted concessions equal to about 25 percent of pay and benefits without any mechanism for recovering those concessions built into their contract. However, management agreed to reopen the facility, which had been shut down, and Kennecott employees received a $1,000 bonus when the contract was signed.