A common volatilization trend in Transantarctic Mountain and Australasian microtektites: Implications for their formation model and parent crater location

We studied the variations of the volatile major elements Na and K in Transantarctic Mountain microtektites and Australasian microtektites with distance from the putative source crater location in Indochina. The dataset includes 169 normal-type Australasian microtektites (101 from this study and 68 from the literature) from 24 deep-sea sediment cores up to 8000 km from Indochina, and 54 Transantarctic Mountain microtektites from northern Victoria Land, 11 000 km due southeast of Indochina. Normal-type (MgO < 5.5 wt.% and SiO2 = 60–78 wt.%) Transantarctic Mountain microtektites and Australasian microtektites share a common volatilization trend with Na and K contents decreasing with distance from Indochina. The average total alkali (Na2O + K2O) concentrations at distance ranges of 1000–2000 km, 2000–4000 km, 4000–8000 km and > 8000 km are 4.27 ± 0.67 wt.% (n = 84), 3.20 ± 1.21 wt.% (n = 50), 2.10 ± 0.25 wt.% (n = 35) and 1.25 ± 0.25 wt.% (n = 54), respectively. The trend highlights a relationship between increasing loss of volatiles in microtektites with longer trajectories and higher temperature-time regimes which should be taken into account in microtektite formation modeling. The trend is consistent with a previous hypothesis that Transantarctic Mountain microtektites belong to the Australasian strewn field and that Indochina is the target region for the parent catastrophic impact.