Which three elements are most often created by cosmic ray spallation?

Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress.

Cosmic rays cause spallation when a ray particle (e.g. a proton) impacts with matter, including other cosmic rays. The result of the collision is the expulsion of particles (protons, neutrons, and alpha particles) from the object hit. This process goes on not only in deep space, but in Earth's upper atmosphere and crustal surface (typically the upper ten meters) due to the ongoing impact of cosmic rays.