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 8000km from Indochina, and 54 Transantarctic Mountain microtektites from northern Victoria Land, 11000km due southeast of Indochina. Normal-type (MgO<5.5wt.% and SiO 2 =60–78wt.%) 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 (Na 2 O+K 2 O) concentrations at distance ranges of 1000–2000km, 2000–4000km, 4000–8000km and >8000km are 4.27±0.67wt.% (n=84), 3.20±1.21wt.% (n=50), 2.10±0.25wt.% (n=35) and 1.25±0.25wt.% (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.