The initial margin is the minimum amount of funds used as collateral to initiate a trading position. If the initial margin requirement exceeds your Free Margin you won’t be able to initiate a trade.  The maintenance margin is the amount of equity in your　account to continue holding your position (s), which is 50% of the initial margin amount.

Initial margin on a major pair (ie 10X leverage) is 10 percent of the desired position size. Initial margin on a minor pair (ie 5X leverage) is 20 percent of the desired position size. Please see here for more details.