Miner Rio Tinto said in the first quarter most of its operation continued to run at capacity with Chinese demand growing strongly and recovery in the West but it was still cautious about short term volatility.Rio Tinto's global iron ore production was up 39% on the first quarter of 2009.Pilbara iron ore production rose 48% on the same quarter last year but down 4% on the previous quarter, partly attributable to restricted availability of car dumpers.Chief executive Tom Albanese said: "In the first quarter, most of our operations continued to run at capacity. Chinese demand grew strongly and we saw some recovery in OECD markets, but we are still cautious about short term volatility. "The long term outlook remains very strong and we are now ramping up our growth projects with sustained investment in our iron ore business and the start of development of Oyu Tolgoi," he added.Mined copper production was down 16% on the first quarter of 2009 due to lower grades at Kennecott Utah Copper and Grasberg.Mined gold and molybdenum production were 12% and 58% higher on the equivalent last year, while Bauxite production increased 18%. Australian hard coking coal production was up 35% and Uranium production was down 20%.