It, like any rock, would turn into a Metamorphic rock.
If a sedimentary rock is exposed to heat and pressure, it may undergo metamorphism and transform into a metamorphic rock. The minerals present in the sedimentary rock can recrystallize and reorganize due to the increased temperature and pressure, resulting in the formation of new minerals and a change in texture.
Slate is the metamorphic rock that forms from shale after it is exposed to heat and pressure for a llllloooooonnnnnnnggggg time.
If igneous rocks are exposed to extreme pressure and heat, they are likely to recrystallize into new igneous rocks. On the other hand, if sedimentary rocks are exposed to extreme pressure and heat, they are likely to metamorphose into metamorphic rocks.
It can happen to anyone that is not hydrated or is exposed to much heat or both.
gneiss
Metamorphic.
Metamorphic rock
When limestone is exposed to intense heat and pressure, it metamorphoses into a rock called marble. Marble is a metamorphic rock that forms when the calcite crystals in limestone recrystallize and interlock.
If you heat steam under pressure you get "superheated steam" under higher than original pressure
Granite, a type of igneous rock, can metamorphose into gneiss when exposed to high temperatures and pressure. Gneiss is a foliated metamorphic rock with distinct layers or banding due to the rearrangement of minerals under heat and pressure.
sedimentary rock
Heat and pressure change shale into metamorphic rock, specifically slate when exposed to low to moderate levels of heat and pressure, and then further into phyllite, schist, and gneiss as the intensity of heat and pressure increases.