Water in tektites and impact glasses by fourier‐transformed infrared spectrometry

To improve the scarce data base of H 2 O content in tektites and impact glasses, we analyzed 26 tektites from all four strewn fields and 25 impact glass samples for their H 2 O content. We used the fourier‐transformed infrared (FTIR) spectrometry method, which permits measurement of areas of ∼40 μm in diameter. Our results show that the tektites have H 2 O contents ranging from 0.002 to 0.030 wt% (average 0.014 ± 0.008 wt%). Ivory Coast tektites have the lowest H 2 O abundances (0.002–0.003 wt%), and Muong Nong‐type indochinites and some North American tektites having the highest contents (up to ∼0.03 wt%). Impact glass samples (from the Zhamanshin, Aouelloul, and Rio Cuarto craters) yielded H 2 O contents of 0.008 to 0.13 wt% H 2 O. Typical impact glasses from the Aouelloul and Zhamanshin craters have low H 2 O contents (0.008 to 0.063 wt%). Libyan Desert Glasses and Rio Cuarto glasses have higher H 2 O contents (∼0.11 wt%). We also analyzed glasses of unknown origin ( e.g. , urengoites; glass fragments from Tikal), which showed very low H 2 O contents, in agreement with an origin by impact. Our data confirm that all tektites found on land have very low H 2 O contents (<0.03 wt% H 2 O), while impact glasses have slightly higher H 2 O contents. Both glass types are very dry compared to volcanic glasses. This study confirms that the low H 2 O contents (<0.05 wt%) of such glasses can be considered good evidence for an origin by impact.