Compositional and Textural Variability Among Tektites From Indochina and South China: Insights Into the Impact Origin of the Australasian Tektite Strewn Field

Abstract

The Australasian tektite strewn field, approximately 0.8 Ma in age, covers nearly 10% of the Earth's surface, making it the largest and most recent strewn field globally. This study provides a comprehensive analysis of the elemental composition and texture of tektites recovered from various locations within the strewn field, particularly Vietnam, Thailand, and South China. These tektites exhibit a consistent major and minor element composition similar to the Upper Continental Crust characteristic of normal tektites. Notable elemental deviations in the concentrations of CaO, FeO, MgO, Pb, and Sr are observed in the Indochina Peninsula tektites, suggesting the mixing of multiple target rock components. Indochinites from Thailand and Vietnam show lower Pb and Sr levels compared to those from China, Indonesia, and Australia, potentially reflecting proximity to the hypothetical impact site on the Bolaven Plateau, Laos. The local stratigraphy of basalts over laterite and sandstone at the proposed source crater site may explain the observed decrease in Pb and Sr concentrations, primarily due to sandstone admixture, while variable MgO, CaO, and FeO suggest a basaltic contribution. The high abundance of lechatelierite inclusions and elevated SiO₂ in Indochinites compared to South China tektites underscore the role of target rock composition in tektite formation. Schlieren flow structures further confirm rock mixing during the early impact stages. Overall, the findings elucidate the relationship between tektite formation, target rock interaction, and impact processes, supporting the Indochina Peninsula as the impact area and highlighting the need for further research on elemental fractionation and target rock heterogeneity.