Computed microtomography of unmelted micrometeorites from the Sør Rondane Mountains Antarctica

: Chemical and structural characterization of unique extraterrestrial matter

Scriptie/masterproef: Master's Thesis

Uittreksel

In this master dissertation, unmelted micrometeorites from the Sør Rondane Mountains in Dronning Maud Land, East Antarctica were studied. The extraterrestrial particles are scanned using the HECTOR μCT instrument from the UGCT. The efficacy of this non-destructive technique in finding high-density relict mineral phases and other structures is evaluated by comparing with SEM-EDS imaging of polished particles. Seventy-three unmelted micrometeorite candidates were selected for CT scanning based on the presence of Ni and Cr detected with μXRF, and on imaging with SEM-EDS. Thirty-five of the scanned micrometeorites were mounted on epoxy cylinders, polished and scanned again using SEM-EDS. The data from the SEM-EDS analysis provided information about internal structures, porosity and mineral phases. μCT data provided information about equivalent diameter, sphericity, number of voxels and surface of the present high-density phases, porosity and matrix. Calculated porosities using the SEM and μCT images are compared to assess the use of lab-based μCT in the characterization of internal structures. The resolution of 4 μm of the μCT instrument has proven to be too low to effectively image pores smaller and around 4 μm in size, leading to an underestimation of the porosity. High- and low-density phases can be imaged to some degree using μCT, but not much information can be gained without chemical characterization. SEM-EDS analysis revealed multiple relict and newly formed mineral phases including chromite, Fe and Ni sulphides and metals, magnetite, pyroxenes, olivines and other spinel group minerals. In future research, other lab-based μCT set-ups from the UGCT group, such as MEDUSA or HERAKLES, may be of interest. μCT is still a powerful technique, which can serve as a good first step in the characterization of micrometeorites, provided with an adequately high resolution.
Datum Prijs28 jun 2019
TaalEnglish
BegeleiderSteven Goderis (Promotor) & Philippe Claeys (Promotor)

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