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 SiO(2)= 6078 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 (Na(2)O + K(2)O) 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 (C) 2010 Elsevier B.V. All rights reserved.