Metal isotope insights into volatilisation during meteorite impact: A Cu isotope study of tektites
Date
2023
Authors
Jolly, J. C.
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Abstract
The enigmatic behaviour of high-temperature element mobility within the solar system and on Earth remains a perplexing scientific phenomenon. This process can be explored through the study of materials formed under analogous conditions, such as high-temperature meteorite ejecta. Tektites thereby provide insight into these processes of metal transport and vaporisation of volatile elements under high temperature conditions. This study uses microscopy, bulk rock compositions, in-situ micro-chemistry, and Cu isotopes for a plethora of tektite shapes and locales to identify, quantify, and chemically assess the distribution of elements within tektites. Furthermore, this study attempts to investigate the chemical heterogeneity of flow banding and shaping for the first time. Examination of tektites through microscopy revealed flow banding of roughly 30 μm thicknesses but vary significantly within each sample. In-situ analysis of these bands indicates favoured extraction and diffusion of moderately volatile elements, such as Cu, Zn, and K, across individual samples on a micron scale. Cu isotope data supports the high temperature fractionation of elements during tektite formation with δ65Cu values (‰) generally increasing with decreasing Cu concentration (ppm). δ65Cu varies across a range of highly fractionated values of 1 to 7‰ and follows Rayleigh fractionation models. This geochemical, and extensive micro chemical analysis presents the first investigation into the composition of flow banding of tektites and heterogeneity between tektite shapes. Furthermore, this study demonstrates that Cu, Zn, and K vary across bands, suggesting intrasample diffusion of elements prior to quenching. Analysis of additional tektites shapes and corresponding in-situ flow banding heterogeneity should be prioritised, accompanied by further investigation into other isotopic systems within tektites.
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School of Physical Sciences
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Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, YEAR
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