phazon was introduced into the story by a meteor that
crash-landed into Tallon-IV filled with "poison"(that's what
the Chozo named phazon) that killed(or mutated)certain
life-forms.meanwhile,the space-pirates were looking for a
power source for their technollogy,searching each and every
planet,killing each and every creature.then,they got readings
from a planet called Tallon-IV,and soon after the Chozo left
the planet 'cause the "poison" the space-pirates and their
newest creation Meta-Ridley,came to the planet and siphoned
the phazon energy.then Samus Aran gets a message from the
Galactic Federation saying there is a distress beacon on a
space-pirate ship,and then that's when Meta-Ridley led Samus
to Tallon-IV,waiting to be seen by the space-pirates...

quite but not so, you forgot to say that in the real way that the phazon was introduced was in the pirate logs and in the mines aslo in the crater.