Interesting question.

From my side, I shall ask first the following question in order to have an answer at this topic. Is the crust homogeneous, or heterogeneous. ? And we found that is heterogenic - continental and oceanic. For oceanic crust, we get answer from paleo magnetism that this oceanic floor is builded due to rift process of magma hot material cristalisation. How about continental floor - need to investigate the paleo magnetism on first ages of our planet crust formation processes.

Huge work. :)