From what I learned,
preignition is the spontaneous combustion of the fuel/air mixture, due to a higher temperature than the octane specification permits. This flame front (shock wave), then collides with the flame front (shock wave) from the normal igntion event.
The collision of the shock waves is the cause of the broken parts. Physical damage.
My understanding of detonation is not as good.
However, I personaly drove my 1978 Ford Fiesta (A GREAT CAR !!!) down the New York State Thruway, everyday, with my foot on the floor. About 90 mph top speed. (1100 cc if I rember correctly).
One day the coolant temp went well over full scale, And I lost all power, maybe 35 mph. It took a while to cool, and I regained power.This happened a few times. The end result was a cracked head. I beleive the cause was fuel starvation, a very lean condition.
Take it away Tony D............