Chinese stocks dived the most in over six years Monday, with a wide sell-off sweeping across the financial sector as investors turned jittery over the latest move by securities regulators to clean up the margin-trading business. The benchmark Shanghai Composite Index SHCOMP, -7.70% plunged 7.7% to close at 3,116.35, posting its biggest daily percentage decline since June 2008 . Prior to Monday’s heavy loss, the index was up 4.4% for the month to date, extending gains after finishing 2014 with a sharp 53% advance. The plunge in mainland China helped to push Hong Kong’s benchmark Hang Seng Index HSI, -1.51% down 1.5%, ... (full story)