.N The mining index .AXMM shed 0.4%, with global miner Rio Tinto RIO.AX and BHP BHP.AX sliding 1.6% and 0.6%, respectively. By Archishma Iyer April 11 (Reuters) - Australian shares closed higher amid choppy trade on Monday, as gains in banks on the prospect of improving margins outweighed weakness in heavyweight mining stocks. Investors' caution persisted as they weighed likely imminent rate hikes by global central banks amid inflationary pressures and heightened Russia-Ukraine conflict.