Alternative Investment: Commodities: Collateral Return

Hi,

Is the collateral return an investor receives from investing in futures on only the capital contributed towards the up-front margin payment? Does the exposure of the futures contract have any bearing on this (ie does the investor invest the difference b/w the exposure of the margin contract and the margin in treasuries)?

Thanks in advance

The collateral return is the return on the amount in the margin account; this amount will change daily.