Location Services uses a mix of wifi/cellular/gps depending on the application. Non-exact or geo-fence type applications should request an estimate location which uses wifi and cellular. Turn-by-turn apps or apps that track your speed will request an exact location every x seconds. These force the use of the GPS.
So even if you see the location services mark appear in the menu bar, it does not mean something is actively using the GPS chip. As far as I know, there's no way to disable only the GPS while keeping the other services available - maybe with a jailbreak, but not on stock.