Table 1: ICP-MS results for U and Th concentrations in DSDP 418A basaltic glass.

Sample nameSample grain size; # grainsSample descriptionSample weight (mg)Th (ppm)U (ppm)Th/U

DSDP-418A-75-3-[120–123]-ICP–MS #1~0.3–1.0 mm; 13(a)5.30.0970.0372.66
DSDP-418A-75-3-[120–123]-ICP–MS #2~0.3–1.0 mm; 42(a)10.40.1290.0373.51
DSDP-418A-75-3-[120–123]-ICP–MS #3~1.5 × 3 × 4 mm; 1(a)17.80.1640.0533.10
DSDP-418A-75-3-[120–123]-ICP–MS #4~1 × 1 × 1 mm; 1(a)1.60.1120.0382.97
DSDP-418A-75-3-[120–123]-ICP–MS #5~1 × 1 × 1 mm; 1(a)1.10.1070.0402.67
DSDP-418A-75-3-[120–123]-ICP–MS #6~50–300 m; 266(b)0.90.1320.0423.16
DSDP-418A-75-3-[120–123]-ICP–MS #7~50–300 m; 263(b)0.90.1170.0353.31
DSDP-418A-75-3-[120–123]-ICP–MS #8~50–300 m; 298(b)1.20.1080.0323.35

For Th and U determinations (ppm), the external reproducibility is 5–10% (2 level) of the quoted abundances.
Sample descriptions:
(a) Test fractions: they comprise predominantly fresh basaltic glass, which also contains numerous small (<100 m) vesicles and their inclusions (e.g., vesicles commonly contain numerous ~1 m sized Fe-sulfide spherules) and possibly some small domains (~a few % by volume) that comprise altered (palagonitized/devitrified) zones and/or phenocryst inclusions such as clinopyroxene and plagioclase.
(b) Pristine, fresh basaltic glass, devoid of alteration, inclusions, or vesicles: the shards of glass are transparent and light tan brown (thinnest shards) to dark brown (thickest shards) in colour. Surfaces invariably show a vitreous luster and comprise curviplanar to conchoidal fractures that impart a myriad of shapes to the grains. All of these grains were found to be isotropic when viewed under petrographic microscope with crossed nicols.
values used for theoretical modelling of alpha-recoil track (Figures 10(h), 10(i), 15(c), and 15(f)) and fission track (Figures 10(g), 15(g), and 15(h)) areal densities in DSDP 418A basaltic glass in this study.