(Adds Andina losses, possible Collahuasi talks, other details, updates copper prices)

By Manuel Farias

SANTIAGO, July 11 (Reuters) - Labor disputes continued on Wednesday at two major copper mines in Chile, the world's top producer of the red metal, as workers backed demands for a heftier piece of the mining industry's booming profits.

At one of Chile's largest copper mines, the Collahuasi mine in the extreme north of the country, miners took their strike into a third day after overnight talks between management and union leaders ended without agreement.

"There was a little progress, but then they put forward another proposal and everything fell apart," one union source said. "In practical terms, we made very little progress."

The president of the union, which represents nearly 700 of the 1,080 directly contracted workers at the mine, later told Reuters talks might resume in the evening.

Collahuasi, majority owned by world mining heavyweights Xstrata Plc <XTA.L> and Anglo American <AAL.L>, produced around 440,000 tonnes of copper last year, or 8 percent of Chile's total.

Management says it has a contingency plan in place to ensure copper output. It has given no details of the impact of the strike. The union says production has been hit and the work force has been reduced to a tenth of its normal level.

The company has offered workers a real-term pay increase of 4 percent, plus bonuses and benefits that, together, would give workers an 8 percent increase in their monthly salaries.

The union says it wants an 8 percent real-term pay raise.

On the COMEX division of the New York Metals Exchange, copper for September delivery <HGU7> gained 0.3 percent to close at $3.62 a lb, partly due to the lingering labor disputes in Chile.

Mining profits have soared as copper prices hit all-time highs of $4 per lb last year, driven by soaring demand in China and elsewhere for cables and other copper goods used in manufacturing, buildings and infrastructure.

ANDINA ON HOLD

Some 1,100 miles (1,750 km) south of Collahuasi, the world's biggest copper mining company, state-owned Codelco, said all operations at its Andina division would remain suspended until at least Thursday morning after a worker was seriously injured in disturbances on Monday.

There was further trouble near Andina on Wednesday morning when striking workers clashed with police at a transport hub used to take employees to their jobs.

The local government and Cristian Cuevas, the main leader of the protests, both confirmed more than 40 people were detained.

Cuevas said five workers were injured and blamed "Codelco criminals" for the clashes, even though he sat down with the company for talks on Tuesday.

A Codelco spokesman at Andina said 700 tonnes of copper output had been lost per day at the plant since Monday and that the strike had cost Andina $25 million in lost copper sales since the stoppage began on June 25.

Andina, 50 miles (80 km) north of Santiago, is the third-largest of Codelco's divisions and produced 248,000 tonnes of refined copper in 2006, some 14 percent of Codelco's total.

This week's disturbances were the most serious yet in a two-week stand-off between Codelco and subcontracted workers who are demanding improved pay and conditions.

The workers are not employed directly by the company but perform tasks like earth clearing, catering, truck driving and cleaning at Codelco mines.

They say they want their salaries brought more into line with the company's unionized staff, who have enjoyed ample pay raises and bonuses as copper prices have soared in recent years, boosting Codelco's profit.

Codelco says it cannot meet the main demands of the subcontracted workers because it is not their direct employer.

(Additional reporting by Antonio de la Jara, Rodrigo Martinez and Gideon Long)

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