** Australian mining sub-index .AXMM up as much as 2.3%, hitting a record high

** Sub-index helped by gains of 2.2% in mining giant BHP Group BHP.AX

** BHP says it remains confident in steady global iron ore demand

** Peers Rio Tinto RIO.AX and Fortescue FMG.AX gained 1.7% and 0.8%, respectively

** Sub-index up 31.5% YTD, including the day's move

(Reporting by Shivangi Lahiri in Bengaluru)

((shivangi.lahiri@thomsonreuters.com))