If the rock at Location 2 (Mudstone protolith) continued to be buried to a depth of 25km and temperature of ~550°C, what rock would it become?

The rock at Location 2, which is Mudstone protolith, would become a metamorphic rock under these conditions. Specifically, it would likely become Slate, Phyllite, Schist, or Gneiss, depending on the exact conditions and the presence of other minerals. These rocks are formed under high pressure and temperature conditions, typically found deep within the Earth's crust. The process of transformation is known as metamorphism.

Here are the steps of this transformation:

1. Burial: The Mudstone protolith is buried to a depth of 25km. This increases the pressure and temperature the rock is exposed to.

2. Metamorphism: The high pressure and temperature cause the minerals in the Mudstone to recrystallize. This changes the texture and composition of the rock.

3. Formation of Metamorphic Rock: The recrystallized minerals form a new rock. The exact type of metamorphic rock (Slate, Phyllite, Schist, or Gneiss) depends on the specific conditions and the minerals present in the Mudstone protolith.

4. Uplift: Finally, tectonic forces can bring the metamorphic rock back to the Earth's surface.