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system
when entering a futures contract, must the margin deposit be idle or can i profit from it?
user
in theory, an fcm may accept various types of collateral, including assets such as cash, treasuries, certain stocks, sovereign debt, letters of credit, and (as of 2009, i think,) gold. in practice, most will want you to post cash or cash. some will take treasuries, but i think you'll generally have a hard time posting securities or other riskier asset classes at most shops, as dealing with the margining around them is more complex (and less profitible).
assistant