Table 1 Sample details.

Origin, ages, internal structures, and α-ejection correction factors of analyzed crystals. Fth and Ftz, α-ejection correction factors for full crystals with assumed homogeneous and measured zoned distribution of U and Th, respectively, calculated using the equation of Farley et al. (29); age difference, the difference between the ZHe age corrected for α-ejection based on measured U-Th distribution (termed “true” age here) and the ZHe age corrected for α-ejection assuming homogeneity of U and Th (termed “conventional” age here). “+” and “−” mean that the true ZHe age is older or younger, respectively, than the conventional ZHe age. Ma, million years; N/A, not applicable.

CrystalOriginMagmatic/
metamorphic age
Conventional
ZHe ages (Ma)
Zircon internal featuresFthFtzAge
difference
I2-9Leucogranite (India)Emplacement at
2029 ± 65 Ma;
overprint at
536 ± 48 Ma (53)
194.7 ± 20.6 to
314.7 ± 18.9 (Table 2)
Oscillatory zoning with two amorphous,
inclusion-rich domains, overgrown by
thin high–CL response rim; traversed
by several radial fractures
0.870.82+5%
I2-1Leucogranite (India)Emplacement at
2029 ± 65 Ma;
overprint at
536 ± 48 Ma (53)
194.7 ± 20.6 to
314.7 ± 18.9 (Table 2)
Oscillatory zoned; low–CL response core
with rounded terminations, overgrown
by high–CL response rims containing faint
indications of patchy and sector zoning
0.880.90−2%
M14-4Variscan batholith
from Sardinia (Italy)
Emplacement at
320–290 Ma (52)
67.1 ± 7.1; 73.7 ± 4.2
(Table 2)
Idiomorphically zoned; rim overgrowing
high–CL response core with invaginated
boundaries
0.780.72+6%
R-3Variscan granite
from Bohemian
Massif (Poland)
Emplacement at
312.5 ± 0.3 Ma (54)
99.7 ± 6.7 to
271.2 ± 24.8 (26)
Oscillatory zoning; low–CL response
mineral inclusions; convoluted
boundaries between some
growth zones
N/AN/AN/A