The sharp sell-off in the gold price this week on the back of concerns over demand has created some buying opportunities across the gold-mining sector, according to Tradenext.Gold slumped by around 9.0% on Monday, its biggest on-day drop since the start of the 1980s as a slowdown in China and price-target downgrades by analysts sparked a dramatic fall, causing gold miners to follow suit.The price has since recovered slightly, up a few per cent over the past few days, but is still way off the near-$1,600 levels seen earlier this month.Gold for June delivery on the Comex division of the New York Mercantile Exchange was trading at $1,394.40 by Thursday morning."In our view, this sell-off has once again created some short- and long-term opportunities to pick these mining stocks up at what could be once-in-a-lifetime low prices," said Ronnie Chopra, Head of Strategy at Tradenext.He said that Tradenext is a buyer of African Barrick Gold, Petropavlovsk, Kazakhmys, Vedanta, Fresnillo and Ferrexpo.However he did recommend traders "of nervous dispositions" to run tight stop losses.BC