From Zerohedge:
Anyone surprised, please raise your hands. And yes, it was fun when margin were hiked only on surges in the various futures contracts. Now, dumps works just as well. The logic, of course, is that gold shorts are also margined. However, judging by the immediate $15 drop in gold upon the announcement, those who are short the metals certainly have a much, much bigger balance sheet and cash hoard to satisfy any collateral requirements than those long. Next: expect the Shanghai Gold Exchange to hike margins in a few short hours once China wakes up and looks at overnight PM prices in horror.
Source: CME Group
Gold Drops Most In 30 Years (Last Week 0Hedge)