Geochemical patterns in Australasian microtektites: implications for the tektite/microtektite formation model

• Main Author: DEL RIO, MATTEO
• Other Authors: Folco, Luigi, Masotta, Matteo
• Format: Text
• Language: Italian
• Published: Pisa University 2023
• Subjects: SCIENZE DELLA TERRA; Antarc*; Antarctica; antartic*; Antartide; Victoria Land
• Online Access: http://etd.adm.unipi.it/theses/available/etd-09272023-110338/

I conducted an in-depth geochemical study of Australasian microtektites (microscopic impact glass particles) from the Transantarctic Mountains (AUS/TAM), Victoria Land, Antarctica, through petrographic and chemical analyses. The Australasian tektite strewn field is the largest (~15% of the Earth's surface) and the youngest (~0.8 million years old) of the five strewn fields so far know on Earth. It is also the most elusive one: despite its enormous size and young age, its parent impact crater has not been identified yet, although several petrographic and geochemical trends suggest an impact location in Indochina or sourrounding seas. Because of the large amount of tektite material available for reasearch from its entire geographic extension, the Australasian tektite/microtektites strewn field continues to provide important clues on several key aspects of the tektite/microtektite formation mechanism which are stil enigmatic. In this work, I focus on geochemical trends in homogeneous populations of AUS/TAM to contribute to the understanding of chemical fractionation during impact melting and hypervelocity ejection. The AUS/TAM studied in this work are from Miller Butte (-72.70, 160.25), Victoria Land, Antartica. They belong to the Italian Programma Nazionale delle Ricerche in Antartide (PNRA) collection and are courtesy of the Museo Nazionale dell’Antartide (MNA). Twenty-eight microtektites were selected based on petrographic and morphological features, as well as minimal degree of weathering, based on optical and scanning electron microscopy (SEM). They were divided into six size classes, ranging from 110 µm to 775 µm, in order to study the geochemical behavior of major and trace elements in relation to size. Geochemical data were determined by electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The twenty eight AUS/TAM have chemical composition consistent with that reported in the literature. Twenty-five belong to normal compostional-type, 2 ...