Hydrodynamic coupling in microbially mediated fracture mineralization: Formation of self-organized groundwater flow channels

• Published in: Water resources research 2014-01, Vol.50 (1), p.1-16
• Main Authors: Mountassir, Gráinne El, Lunn, Rebecca J., Moir, Heather, MacLachlan, Erica
• Format: Article
• Language: English
• Subjects: biomineralization; Calcite; flocculation; Flow channels; Flow rates; fracture flow; Groundwater flow; Hydrodynamics; Microbial activity; microbially induced calcite precipitation; Microorganisms; Mineralization; ureolysis
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1002/2013WR013578

Evidence of fossilized microorganisms embedded within mineral veins and mineral‐filled fractures has been observed in a wide range of geological environments. Microorganisms can act as sites for mineral nucleation and also contribute to mineral precipitation by inducing local geochemical changes. In this study, we explore fundamental controls on microbially induced mineralization in rock fractures. Specifically, we systematically investigate the influence of hydrodynamics (velocity, flow rate, and aperture) on microbially mediated calcite precipitation. Our experimental results demonstrate that a feedback mechanism exists between the gradual reduction in fracture aperture due to precipitation, and its effect on the local fluid velocity. This feedback results in mineral‐fill distributions that focus flow into a small number of self‐organizing channels that remain open, ultimately controlling the final aperture profile that governs flow within the fracture. This hydrodynamic coupling can explain field observations of discrete groundwater flow channeling within fracture‐fill mineral geometries where strong evidence of microbial activity is reported. Key Points Feedback between velocity & microbially induced calcite precipitation This results in a small number of self‐organizing stable channels Our results explain field observations of microbially mediated precipitation