Ages of Old Earth Zircon Grains
(D. Trail & S. Mojzsis)
They measured the age as a function of the depth:
Cores, which are igneous, are roughly 4.2Ga. Mantles less than 3.9Ga
All
samples have "impacts" at ~3.95 Ga
Cores, which are igneous, are roughly 4.2Ga. Mantles less than 3.9Ga
All samples have "impacts" at ~3.95 Ga