Cut the cheesecake into quarters and thaw according to package instructions. In a large saucepan over medium-high heat combine the marmalade, orange liqueur, orange juice concentrate, and orange slices. Simmer until thick and syrupy, about 10 minutes.
To serve, spoon warm orange spice mixture over the top of cheesecake slices.
NOTE: Use blood oranges in the winter season for a red, festive touch