Complex sentence: The magmatism and petrogenesis of continental crust is complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.
Split into simpler sentences: The magmatism and petrogenesis of continental crust is complicated due to the involving of both oceanic crust and continental crust. In essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.