Table 2.

Radiation dosage calculation

Alpha-dose calculationn3847-30n3852-08n3844-47
238U, ugg−11654,9171,614
232Th, ugg−181211378
Upper intercept 207Pb/206Pb age, Ma3,3002,8103,680
Dose since upper intercept age3.0 × 10183.4 × 10199.4 × 1019
Dose since metamorphic age, 2,500 Ma2.0 × 10182.8 × 10195.1 × 1019
Dose radiation between formation and metamorphism1.0 × 10185.2 × 10184.3 × 1019
Grain did not reach the first percolation pointGrain could have reached the first percolation point, but not the secondGrain reached second percolation point
Not metamictMetamictHighly metamict grain