Jan 21 (Reuters) - Australian shares fell on Friday amid a sell-off across sectors, as stocks of mining giant Rio Tinto dropped, gold and mining companies dipped, and cases of the Omicron coronavirus variant in the country continued to surge. The benchmark S&P/ASX 200 index (.AXJO) was down 1% at 7,342.4 points by 2337 GMT, losing 1.6% for the week so far — its worst weekly performance since Oct. 1. Investors" concerns grew after Western Australia cancelled plans to reopen its borders on Feb. 5, citing health risks from spiking Omicron cases elsewhere in the country. read more Miners (.AXMM) led the declines on the ASX 200, shedding 2.5% to eye their first weekly loss after eight straight weeks of gains. Global iron ore giant BHP Group (BHP.AX) lost 2.6% after its investors in London and Sydney approved plans to scrap its dual listing in favour of a main listing in Sydney. read more Meanwhile, rival Rio Tinto"s (RIO.AX) shares dropped more than 2.4% after Serbia revoked its lithium exploration licences on environmental grounds. Rio was, however, set to gain for the ninth straight week. read more Gold stocks (.AXGD) fell 1.7%, dragged by Evolution Mining Ltd"s (EVN.AX) over 1.9% slide. Tech stocks (.AXIJ) were down 1.5%, hitting their lowest since May 20, while the energy index (.AXEJ) slid 1.4% amid weaker oil prices. Coal miner Whitehaven Coal (WHC.AX) dropped 10.2% in its worst session since Nov. 2. It was also one of the biggest losers on the benchmark after posting a weak quarterly production and subdued outlook for 2022. read more Banking stocks (.AXFJ) followed suit, declining 0.7%. Major lender Australia and New Zealand Banking Group (ANZ.AX) also fell 0.7%. In New Zealand, the benchmark S&P/NZX 50 index (.NZ50) slid 0.9% to 12,497.1. Motorhomes seller Tourism Holdings Ltd (THL.NZ) led losses, falling 2.8%. Elsewhere, the S&P 500 E-minis futures were down 0.5%.