* Composition: Rhyolite is a felsic igneous rock, meaning it's rich in silica and has a high proportion of light elements like potassium and sodium. This composition is associated with the remelting of existing continental crust, which is itself rich in these elements.

* Melting Process: The formation of rhyolitic magma often involves the partial melting of continental crust due to:

* Subduction: As oceanic plates subduct beneath continental plates, the descending plate releases fluids that can cause melting in the overlying continental crust.

* Extensional Tectonics: In areas where continental crust is being stretched, the lower crust can experience decompression melting.

* Oceanic Crust: Oceanic crust is composed primarily of basalt and gabbro, which are mafic rocks with lower silica content. While some rhyolitic magma can form in association with volcanic arcs above subduction zones, it's less common than in continental settings.

In summary: Rhyolitic magma is most likely to form in continental settings where the pre-existing crust provides the necessary composition and melting conditions.