Gold prices plunged as much as 4 percent to their lowest in more than five years on Monday as sellers in top consumer China offloaded the metal. Spot gold fell $45.55 to its weakest since March 2010 at $1,088.05 an ounce shortly after the Shanghai Gold Exchange opened, with volumes soaring to a record. It regained some ground, trading above the key $1,100 support level, but was still down 1.8 percent at $1,113.80 an ounce by 1002 GMT.