MELBOURNE, July 28 (Reuters) - Rio Tinto (RIO.AX) logged a record first half performance on Wednesday, underpinned by soaring iron ore prices on strong demand from China, which led the global miner to pay out a bonanza of $9.1 billion in dividends.

Rio's half-year underlying earnings more than doubled from a year earlier as a massive infrastructure push by China, the world's top iron ore consumer, and supply problems in Brazil drove prices of the steel-making commodity to record highs earlier this year.

"It's an amazing result, even it is all driven by commodity prices," said Brenton Saunders, a portfolio manager at Pendal Group, a Rio investor.

Rio, the world's top producer of iron ore, said the average realised price for the commodity nearly doubled to $168.40 per dry metric tonne free on board from a year earlier. read more

The price jump helped drive the miner's underlying earnings to $12.17 billion from $4.75 billion a year earlier, beating a consensus of $12.01 billion from 14 analysts compiled by Vuma.

The company declared a special dividend of $1.85 per share and an interim dividend of $3.76 per share, beating expectations by around 6%, and more than tripling last year's total payout of $1.55 for the first half.

"We expect another sizable dividend from Rio in 2H (the second half) as well. The capital return story here is compelling," Jefferies analysts said in a note.

Rio appears to be shifting from austerity and capital returns to more of a focus on growth, as it has committed to its $2.4 billion Jadar lithium-borates project.

Rio Tinto brought forward its investment decision that was expected later in 2021, given the strong demand for the raw material for electric vehicle batteries.

"It's such a low cost and large deposit there, we are trying to bring it to market as soon as we can," Rio Tinto Chief Financial Officer Peter Cunningham told Reuters.

Still, after a less than stellar operational first half, which Rio blamed on poor weather and COVID-19 restrictions, Rio is in danger of losing its crown as the world's largest iron ore producer to Vale (VALE3.SA) , after guiding to production at the lower end of forecasts this year.

"We do think the second half is going to be stronger," said Cunningham. "We certainly feel it was a tough first half, but we certainly feel that we are coming through that," he said.

Cunningham declined to comment on whether the miner had been contacted by regulators after a report by the Financial Times that Britain's financial watchdog is conducting a probe into its $6.75 billion underground copper project in Mongolia.

Rio Tinto shares were down 0.3% in London, but were outperforming rival BHP Group's (BHPB.L) shares, which were down 1.5%.

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