有色金属与贵金属板块走低：美铝等跌超2%，期银跌超9%

Group 1 - The non-ferrous metal sector experienced a decline on December 31, with significant drops in companies such as Alcoa and Century Aluminum, both falling over 2%, while Kaiser Aluminum and Southern Copper saw declines exceeding 1% [1] - The Chicago Mercantile Exchange raised margin requirements for precious metal futures for the second time this week, aiming to cool down the recently surging precious metals market [1] - As a result of the increased margin requirements, precious metals experienced a substantial drop, with New York silver futures falling over 9% and dropping below $71 per ounce [1]