I think I read speculation that lava/magma originates from 20-30 km depth and may originate possibly from naturally occuring nuclear fission reactions.

This may create the heat which creates the high pressures....

I wonder what the he3/he4 ratio is for lava (but which is probably contaminated by reaction with the atmosphere where the light gases quickly rise...giving a bad measurement).

$.02

p.s. Didn't you post this a long while ago Don?