Constraining the Thermal History of Tektites by Matching Temperature Dependent Silica Diffusion Models to the SiO2 Diffusion Profiles of Lechatelierite Inclusions

Abstract

Tektites, a rare melt-ejecta product from impact cratering events, have a formation process that is poorly understood. Different models of formation have been proposed that assume thermal histories of tektites, but there has been little physical evidence to validate these models. Macris et al. (2018) utilized lechatelierite inclusions, which are high temperature, shock-melted quartz inclusions found within tektites, and their diffusion profiles to constrain the expected thermal history of tektites. They utilized an effective binary diffusion model of SiO2 to match their concentration data of indochinite tektite sample LTS1 to a diffusion profile, then estimated the thermal history. Since that paper, Yu et al. (2019), has proposed a new temperature dependent model of SiO2 diffusion. This thesis combines forward modeling of tektite cooling in air with that of temperature-dependent and concentration-dependent SiO2 diffusion, and applies the modeling to the SiO2 profiles found in the Macris et al. (2018) paper. The updated silicadiffusion model matches the Macris et al. (2018) diffusion profiles with less time heating at the initial temperature: ~42s rather than ~70s. Additionally, the maximum initial temperature before cooling of the LTS1 tektite can be constrained to approximately 2650K. The results provide constraints on the thermal history of tektites as well as hydrocode modeling of the impact process. In addition, the method developed here may be applied to investigate other tektites from other strew fields.