The USDC collateral is currently invested with Aave.
Real-time stats: https://polygon.iron.finance/treasury
USDC tokens used as collateral for the minted IRON stablecoin tokens is stored in the protocol’s time-locked collateral smart contract, however, in optimal conditions, the daily redemptions are only a small part of the supply of IRON token. In this case, a large portion of this collateral is idle and economically speaking inefficient. Vaults changed this by investing a large portion, but not all of the USDC token collateral to generate passive income to the protocol and to the TITAN single token staking pool to incentivize TITAN purchases and staking.
Out of all the USDC the protocol stores as collateral, a maximum of 75% is invested into Vaults, while the remaining 25% is kept by the protocol to serve the daily redemptions of IRON token.
If this 25% of all the USDC collateral, stored in the protocol’s time-locked collateral smart contract, serving the daily redemptions of IRON token, decreases to 15% or less, then the Vaults will withdraw some of the invested USDC tokens back to the protocol.
Invested Collateral Ratio is the percentage of all the USDC collateral that is set to be invested via the Vaults to generate income to the TITAN single token staking pool and to the protocol.
Effective Reserve Collateral Ratio is the present percentage of all the USDC the protocol stores as collateral that is not invested with the Vaults but kept in the protocol to serve daily IRON token redemptions.
Reserve Threshold Ratio is the set percentage of all the USDC collateral the protocol stores for the IRON redemptions, at which percentage level the protocol will withdraw some of the USDC investments from the Vaults to have more USDC collateral at the protocol for the IRON token redemptions.