July 11 (Reuters) - Australian shares posted small gains on Tuesday in thin trading as investors awaited the start of major second-quarter U.S. earnings reports and Federal Reserve Chair Janet Yellen's congressional testimony later this week.
The S&P/ASX 200 index, which rose on Monday, added 0.2 percent to 5,737.30 at 0230 GMT, helped by gains in basic materials and energy shares.
Miners benefited from a sustained rally in iron ore prices, as the most-traded iron ore on the Dalian Commodity Exchange rose for a third straight day.
That sent shares of heavyweight miners BHP and Fortescue Metals Group up 1.2 percent and 3 percent respectively.
Rio Tinto shares were up about 0.5 percent but gains were capped by a slump in base metal prices, with copper falling to its lowest since June 27 on Monday and aluminium seeing its biggest single-day drop in over two months.
A slight rise in oil prices fuelled further share-price gains for stocks of Aussie oil and gas majors, with sector bellwether Woodside Petroleum up about 0.6 percent and fuel supplier Caltex Australia nearly 1 percent higher.
Aussie financials were among the top gainers for a second day with the 'Big Four' banks, seen as a barometer of the sector's health, climbing between 0.2 percent and 0.6 percent.
Volumes across the board are expected to remain weak as investors watch for Yellen's monetary policy testimony on Wednesday and Thursday for clues on when the Fed will again tighten U.S. monetary policy.
"Most people have positioned their portfolios ahead of this (Yellen's testimony) and very few people are prepared to react if she does really go into little more depth about her own personal views on financial conditions," said Chris Weston, an institutional dealer with IG Markets.
"Her views at the moment are well known to the market and it shouldn't be too surprised by what she's saying now."
New Zealand's benchmark S&P/NZX 50 index was 0.4 percent, or 31.87 points, higher at 7,615.82 helped by consumer staples and telecom shares.
Dairy products maker a2 Milk and telecom firm Spark New Zealand were among the biggest gainers on the benchmark, up 3.7 percent and 1.1 percent respectively.
While gains were largely broad-based, the energy sector saw some weakness with fuel retailer Z Energy slipping. (Additional reporting by Chandini Monnappa; Editing by Richard Borsuk)