Final answer:
Passive margins typically experience little to no metamorphism due to tectonic stability; instead, they are characterized by sediment deposition. During the late stages of orogeny, a region transitions from an active to a passive margin, leading to the deposition of fine sediments and carbonates without significant metamorphism.
Step-by-step explanation:
The type of metamorphism that occurs in a passive margin is typically very low-grade or non-existent, as passive margins are characterized by tectonic stability with little to no compression or heating that would drive metamorphic processes. Instead, they are primarily sites of sediment deposition. During the late stages of orogeny, a mountain building event, a region transitions from an active margin, where high-grade metamorphism occurs due to continental collision, to a passive margin once again.
This change leads to the deposition of fine sediments and shallow marine carbonates. It's important to note that the transition doesn't involve significant metamorphism because the conditions necessary for metamorphism, namely high temperatures and pressures, are greatly reduced. In the context of the Appalachian Mountains, the Taconic and Acadian orogenies are two periods where high-grade metamorphic rocks would have formed due to continental collision, and after each event, the uplifted mountainous terrain would erode away, transitioning to a state more consistent with a passive margin over time.