Multimodal Mass Spectrometry Imaging of Geologic Samples

In this thesis, a combined analytical approach was used to characterize the spatial distribution of organic material within a geologic sample from the organic carbon-rich Oxford Clay Formation, UK. Analytical methods employed here include the traditional organic geochemistry technique gas chromatography – mass spectrometry (GC-MS) as well as multiple microscopy and MS imaging techniques. The sample preparation techniques detailed in Chapter 2 enabled the multimodal surface analysis of the mounted geologic sample P89-13 of the Oxford clay, including via the MS imaging techniques femtosecond – laser desorption postionization – mass spectrometry (fs-LDPI-MS) and time of flight – secondary ion mass spectrometry (ToF-SIMS). In Chapter 3, ToF-SIMS imaging was used to detect biomarkers within the Oxford clay and to determine that the spatial distribution of those biomarkers was heterogenous throughout the sample. In Chapter 4, scanning electron microscopy – energy dispersive spectroscopy (SEM-EDS) and statistical analysis, including machine learning (ML) was performed on the ToF-SIMS spectra in order to deconvolute the complex signal produced from the Oxford clay. In addition to characterizing sample properties, the multimodal approach employed here also helped constrain the capabilities of the instruments used for the analysis. The results of this work may be useful for the analysis of samples returned from Mars. In the future, the techniques developed for this thesis can be improved and applied to other terrestrial geologic samples and samples analyzed in situ by mass spectrometry on other planetary bodies.