In the above case, rock L and rock F does not undergo contact metamorphism because the rock unit F was only deposited after the intrusion of the rock layer L.
Explanation:
Contact metamorphism rocks are formed as a result of static thermal metamorphism and high temperature at regions adjacent to hot intrusive igneous rocks within the metamorphic zone called the contact aureole. This takes place either through heat contact or contact alternation metamorphism. When the hot molten magma reaches an already formed rock body, the older rock body will undergo changes due to hot magma infiltration.
In the above case, rock I does not undergo contact metamorphism because the rock unit F deposited earlier in the process.
The contact metamorphism can occur only within a small radius ( mostly 1-10 km) of the contact aureole which is heated by the hot magma. The heat should be sufficient enough to break the adjacent rocks and change their structure. The timing of formation of both rocks is also a gradient deciding contact metamorphism between both rocks.
