Mining stocks led the sell-off on Thursday as the US Federal Reserve yesterday painted a gloomy picture of the state of the US economy, dampening sentiment across global stock markets."Information received since the Federal Open Market Committee met in August indicates that economic growth remains slow," the minutes from the meeting of the Federal Open Market Committee (FOMC) read. Several blue chip miners lost over 10% of their value.Worries of a dip in demand for mineral resources sent commodity prices across the board tumbling. By 14:25, copper, gold and silver prices were 6.4%, 3.6% and 7.9% down, respectively.Copper miner Antofagasta was the biggest faller, dropping nearly 12%, not helped by the news that Pakistan's Baluchistan province has voiced objections to a mining lease for a significant copper and gold project in the country's southwest region. Antofagasta has partnered with Barrick Gold for the now delayed joint venture, which has seen them already spend $200m on purchasing the exploration licence from BHP. FTSE 100 mining peers Vedanta, Rio Tinto, Fresnillo and Kazakhmys were also heading significantly lower. Meanwhile, the alternative energy sector is the only category making gains, with solar power wafers manufacturer PV Crystalox Solar among the few stocks rising higher.BCTop performing sectors so far todayAlternative Energy 8,800.34 +0.08%Bottom performing sectors so far todayPersonal Goods 21,597.55 -9.37%Mining 18,709.96 -8.40%Industrial Metals & Mining 4,958.22 -8.26%Forestry & Paper 5,202.57 -6.58%Life Insurance 3,359.20 -5.84%