The big question with decay-rate dating is the question of whether ANY heavy metals which we find near the Earth’s surface are native to our planet or arrived via impact events. Given the standard idea of our planet having formed from swirling masses of solar material, you’d expect all the heavy metals to be at the center and nowhere near the surface.
“Given the standard idea of our planet having formed from swirling masses of solar material, you’d expect all the heavy metals to be at the center and nowhere near the surface.”
There are several reasons they appear near the surface.