How could a metamorphic rock change into a igneous rock?

The only way to create an igneous rock is to create a melt. Therefore, to turn a metamorphic rock into an igneous rock, you have to keep heat and pressure rising on the rock, until the minerals melt. read more

A metamorphic rock doesn't actually change into an igneous rock, as the process of melting results in a melt, which crystallizes into a completely different kind of rock, rather than a gradual transition in form and mineralogy. read more

Metamorphic Rock Formation from igneous rocks is caused by heat and pressure. This is most often the result of mountain building. Plate Tectonics and Mountain Building When the plates of the earth collide, they squeeze the rocks at the borders with unbelievable force. read more