Shareholders in Kaz Minerals have taken fright at news it plans to buy a remote copper project in the far east of Russia from a consortium of investors including Chelsea Football Club owner Roman Abramovich for $900m (£689m). The FTSE 250 miner described the Baimskaya asset in Chukotka, the most easterly region of Russia, as one of the top 10 undeveloped copper projects globally. But investors sent the stock down 25pc to 611p in morning trade amid concerns that Kaz could be overstretching itself.