Talk
Colloquium: Dr. Qian Tian - From Diatoms to Diagenesis: The Formation and Transformation of Biogenic Silica
When
· 12:20 PM MST
Shown in the venue’s time zone (America/Denver), not yours.
Where
Boulder, CO
Tickets
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What the source said
Dr. Qian Tian INSTAAR visiting scientist; Institute of Subtropical Agriculture, Chinese Academy of Sciences Topic: From Diatoms to Diagenesis: The Formation and Transformation of Biogenic Silica Academic Host: Shaily Rahman Abstract: Biogenic minerals provide a link between biological processes and the geological cycling of elements, yet their composition and reactivity can continue to evolve from formation through burial. Diatom biogenic silica provides a particularly useful system for exploring this continuum. Continental weathering supplies silicon and other elements to aquatic environments, where diatoms convert dissolved Si into biogenic silica. Following deposition, biogenic silica may be recycled through dissolution, preserved in sediments, or transformed into secondary minerals during early diagenesis. How the properties acquired during biomineralization influence these subsequent transformations remains poorly understood. In this talk, I will present our work on the interactions among Si, Al, and Fe during diatom biomineralization. We have shown that diatom frustules can serve as an important sink for Al, that Al occurs in distinct structural and surface-associated forms in diatom-derived silica, and that Al incorporation influences silica stability. We further found that Fe availability modifies Al incorporation, demonstrating that the chemical properties of biogenic silica are sensitive to the environment in which it forms. I will also briefly draw on our work on Fe-bearing clay minerals to illustrate how mineral structures and reactive interfaces can continue to respond to environmental change after formation. These observations motivate the next stage of my research: understanding the fate of diatom-derived Si during early diagenesis. In particular, I am interested in reverse weathering, through which reactive silica can be transformed into authigenic aluminosilicate minerals, with implications for sedimentary Si cycling and alkalinity. I will discuss an emerging experimental approach that combines Si isotope labeling during diatom growth with mineralogical and microscopic characterization to follow biogenic Si through dissolution and secondary mineral formation. By linking biomineral formation with post-depositional transformation, this framework aims to clarify how biogenic Si is partitioned among recycling, preservation, and authigenic mineral formation, and how early diagenesis modifies the geochemical signals ultimately preserved in sediments.