Senators demanding answers on what caused the 2008 global economic meltdown were to grill Goldman Sachs chief Lloyd Blankfein Tuesday on the investment giant's alleged role in the collapse. The US Senate Permanent Subcommittee on Investigations was to question Blankfein and other executives including Fabrice "Fabulous Fab" Tourre, the London-based French national at the heart of US fraud charges against the firm.