Rio Tinto Ltd's expansion campaign in the Pilbara region is further boosted as the mining giant formally unveiled the operation of its $US1.5 billion Brockman 4 iron ore mine site in Western Australia.

The resource company said that Brockman carries an initial capacity output of 22 million tonnes per annum and that production capability would be doubled once Rio Tinto's exhaustive expansion plans get underway.

Rio Tinto iron ore and Australia chief executive Sam Walsh said that Brockman 4's initial output is right on track and complements the company's 220 million tonnes per annum capacity.

Mr Walsh added that the new facility's substantial production capacity is greatly supportive of the mining firm's "ability to add high value sustaining tonnage, on time and within budget, as we prepare for our next major phase of expansion."

Rio Tinto is in the middle of its campaign to boost its Pilbara production capacity by as much as 330 million tonnes per annum, which the company said would be realised by 2015 as it added that the Brockman 4 mining site would be a significant contributor to the ongoing expansion drive.