Collaborative Research: Testing Models of Calcite Microcrystal Diagenesis Through Experiments, Geochemistry, and Advanced Imaging

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The resources contained in underground geologic reservoirs are key to the economic activity and vitality of communities, companies, and countries. To develop these resources in a cost-effective manner, it is vital to understand the plumbing of these reservoirs-specifically how big the pores (open spaces) are in the rocks, how well they are connected, and what kind of fluids they hold. This study focuses on small pores, called micropores, to understand how they form, and how they change as they are buried in the Earth. This knowledge will allow people such as farmers, water plant managers, and the oil and gas industry to drill fewer wells, increasing their economic competitiveness and decreasing disturbances to the environment and people. Micropores are also responsible for premature deterioration of roads constructed with crushed limestone. Therefore, the results from this work could lead to more robust highways, reducing construction and maintenance costs, while providing a safer and smoother ride for drivers. Previous work shows that most micropores are hosted in a framework of calcite microcrystals. The current research aims to understand the fundamental controls on the textures of these microcrystals in limestones. Numerous generalized pathways for calcite microcrystal formation and evolution have been proposed. None, however, has tied microcrystal texture to diagenetic process in a robust manner. Our aim is to integrate laboratory experiments, advanced imaging, and high-resolution geochemical techniques to better understand the diagenesis of calcite microcrystals and thus the micropores between them. Specifically, we propose to use experiments and a wide variety of natural samples to assess the geochemical heterogeneity and genetic evolution of the various calcite microcrystal textures. We hypothesize that spatial variations in microcrystal chemistry will reveal that the different microcrystal textures correlate to positions along a diagenetic trajectory of increasing cementation (i.e., microcrystal textures become more fitted with progressive burial and cementation).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.