Imaging of Geologic Samples Using Femtosecond – Laser Desorption Postionization – Mass Spectrometry

This study uses an MS-imaging method developed by Luke Hanley at the University of Illinois at Chicago, femtosecond – laser desorption post ionization – mass spectrometry (fs-LDPI-MS), which has the ability to make molecular maps of hydrocarbons across the surface and with depth of a sample, to study geologic material for the first time. We used fs-LDPI-MS in tandem with previous geochemical characterization and petrographic analysis to precisely determine the spatial distribution of hydrocarbons at the micron scale within geologic material. We performed analysis on two samples to observe the relationships between biomarkers and their mineral matrix. (1) A 93.5 million year old (Ma) sample which was deposited in the Western Interior Seaway (WIS) and (2) a 2.69 billion year old (Ga) sample from the Abitibi Greenstone Belt in Ontario, Canada. By observing hydrocarbon-host rock relationships, we were able to test hypotheses regarding the timing and mode of indigenous, non-indigenous, and contaminant biomarker emplacement within the samples. We were able to create a depth profile of a suite of contaminants emplaced within the 93.5 Ma sample and also to produce MS-images which display the spatial distribution of isorenieratene derivitives within the sample. We were also able to observe hydrocarbons within the 2.7 Ga samples, but we were unable to definitively locate or precisely date the biomarkers previously observed within the Archean samples.