BlackRock, the mammoth U.S. investment manager with USD414 billion under management, is gearing up to manage a single tranche collateralized debt obligation referenced to synthetic asset-backed securities. The portfolio comprises USD325 million of credit-default swaps on ABS, as well as USD175 million of cash assets, according to an official close to the deal. Named Tourmaline, it was structured by Morgan Stanley. Structuring and sales officials at BlackRock in New York and Morgan Stanley in London declined comment. The maturity and target notional of the deal could not be determined.