The London Metal Exchange took action to calm turmoil in the copper market late on Tuesday by introducing temporary limits on some prices, after a plunge in stocks of the metal in its warehouses disrupted trading. The LME said it would adjust its rules requiring large holders of the metal to lend it back to the exchange. It also said it would bring in a limit on backwardation — a scenario whereby spot contracts trade at a premium to futures contracts, indicating that the market is undersupplied. Robust demand and rising copper prices pushed inventories of copper on the LME...