Chemical Analysis of a Lunar Meteorite by Laser Ablation Mass Spectrometry

Master's Thesis from the year 2016 in the subject Physics - Applied physics, grade: 5.5, University of Bern, language: English, abstract: The lunar meteorite SaU 169 was investigated with a miniaturized laser mass spectrometer (LMS). SaU 169 consists of two different lithologies, a regolith breccia and an impact-melted breccia. The latter is extremely enriched in potassium, rare earth elements and phosphorus (K-REE-P) as well as the radioactive elements uranium and thorium, which makes it special compared to other known meteorites. The chemical composition of a meteorite can bring insight into its formation conditions.

In a first step a set of relative sensitivity coefficients (RSCs) was determined by measurements on the regolith rock. Afterwards the chemical composition of the K-REE-P rock was successfully measured and mapped in an elemental composition map. The present minerals (e.g. zircon, ilmenite, pyroxene and K-feldspar) could be identified by analyzing elemental ratios. Special emphasis was put on the mineral zircon. Rare earth element patterns could be measured inside a zircon grain. With the amount of titanium found inside the zircon grain, the crystallization temperature of the grain could be estimated. This again can help determine whether or not the analyzed grain crystallized during an impact event or not. In the last part of this thesis the LMS instrument was coupled with a HV pulser. The HV pulser greatly enhances the detection sensitivity for heavier elements by preventing the lighter elements from reaching the detector and thus avoiding saturation effects on the detector. With the help of the HV pulser the mass spectra of rare earth elements could be readily recorded with sufficiently high signal-to-noise ratio and mass resolution to make a quantitative analysis possible. Uranium and thorium were detected as well at limited sample locations. Also lead was measured but only in one spectrum. With the lead and uranium abundance determined from the