Applications of Laser Ablation Inductively Coupled Plasma Mass Spectrometry in Microbialites

Abstract

Microbialites are critical for documenting early life on Earth and potential early life in other regions of the solar system. However, the criteria for identifying microbialites remain controversial. Trace element geochemistry provides two types of information that aid in the recognition of putative microbialites. First, as most microbialites are composed of authigenic precipitates, trace elements can be used to investigate the fluids involved in their formation, thereby helping to identify paleoenvironmental conditions. For example, rare earth elements (REEs) preserved in microbialites are highly useful in distinguishing depositional environments. Second, microorganisms utilize and accumulate significant quantities of elements, including many metals. The preservation of such elemental enrichments may offer valuable biomarkers. Although research in this field is relatively nascent, high-precision in situ measurements (now with spatial mapping) of metals in microbialites-using techniques such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) have confirmed persistent enrichments of biologically significant metals in microbialites. Consequently, trace element studies are increasingly proving valuable for investigating microbialites. Provided that diagenetic effects and the extent to which specific precipitates represent microenvironments are considered, trace element signatures may yield critical insights into depositional environments and metabolic processes within biofilms.