Skarn is a metamorphic rock formed by the metasomatism of pre-existing rocks, primarily carbonate rocks like limestone or dolostone, by the intrusion of igneous rocks.

So, while skarn is not directly derived from a single "parent rock", the carbonate rock is considered the protolith or source rock for skarn formation.

It's important to note that the igneous intrusion also plays a crucial role in the formation of skarn. The heat and chemical fluids from the intrusion interact with the carbonate rock, leading to the formation of skarn minerals.