Probing the Origins of Carbonate Precipitation by In Situ Nanoscale Microbe-Mineral Analysis and Mapping
EMSL Project ID
49243
Abstract
Calcium carbonate (CaCO3) precipitation through geological time has sequestered large amounts of CO2, but identification of non-skeletal CaCO3, especially bacterial, precipitates is often difficult. Bacterial carbonates are unusual in having an exceptionally long geologic record and remaining widespread and diverse today. Yet even in present-day bacterial carbonates, identifying the organisms, metabolic processes, and environmental controls involved in their formation can be challenging. These difficulties are greatly magnified in ancient deposits that have experienced alteration over million-year time-scales. We postulate that microbial fabrics in geological carbonate rock samples can be recognized by submicron chemical mapping, because these techniques can reveal the distribution and identity of compounds and elements localized by bacterial growth and activities, and are likely preserved in rocks. Working with EMSL scientists, we aim to conduct proof-of-principle analyses to identify and map previously unresolved mesoscopic compositional details in samples from deep time. Our aim is to spatially characterize elemental and molecular components in microbial CaCO3 fabrics using ToF-SIMS and NanoSIMS. Resolution of these chemical signatures could reveal previously undetected spatial patterns and compositional details. Our target samples will be CaCO3 fabrics classically regarded as microbial. These will include fine-grained aggregates (peloids) that may be clusters of self-calcified cells, putative biofilm formed by bacterial communities, tubes and strands resembling bacterial sheaths and filaments, and associated fine-grained carbonates interpreted to form by calcification of cells, EPS and mats. For decades, observations by optical and electron microscopy have shown these fabrics in morphological detail without being able to solve fundamental questions regarding their origins. By applying these techniques of nanoscale resolution and analysis we aim to obtain spatial recognition of organic and inorganic compounds and their associations that will assist discrimination of microbial and inorganic precipitates. Our specific goals are to test this approach in selected carbonate samples by characterizing: (1) elemental distributions and stable isotope fractionation; (2) organic matter preservation, and (3) the presence and the distribution of microbial-derived organic compounds (biomarkers).
The samples to be used for these analyses are carefully selected from recent fieldwork on several continents. Success in this collaborative proposal will provide valuable new data for grant renewal request. Additionally, the new data will allow future optimization of the method for wider application to geological materials. Results from this collaborative research will be presented in upcoming national/international conferences and will provide the foundation for a peer-reviewed article to be prepared this year.
The significance of this research is that it is a proof-of-principle experiment that could constitute a game-changing advance in the investigation of microbial components in geologic materials, by utilizing EMSL nanoscale analytical facilities. If successful, this approach could be used to shed new light on the early history of life on Earth and, potentially on other planets, and would be directly relevant to the DOE clean energy mission. The research we propose is significant for understanding a wide range of microbial carbonates and this understanding is broadly applicable to CO2 sequestration in modern day and through geological time. Success in this pilot project would open up a wide range of cognate studies in carbonate sediments. The project is designed to result in collaborative research and publications with EMSL staff, to provide a foundation for further joint projects at the forefront of this exciting field. Similar techniques could also be applied to other bacterial mineral deposits, e.g., silica, iron oxide, and Ca-phosphate.
Project Details
Start Date
2016-02-29
End Date
2016-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members