Award: OCE-1923802

The unresolved "missing sink" in the global silicon (Si) budget has long puzzled oceanographers. Recent advancements have highlighted reverse weathering processes and the associated production of marine secondary clays as critical mechanisms that could potentially close this budget. While substantial progress has been made over the last decades in understanding the mechanisms underlying authigenic clay formation, significant gaps remain. Key questions include identifying the driving geochemical factors, quantifying marine secondary clay formation in natural environments, and understanding its spatial variability. This project focused on investigating the fundamental drivers of marine secondary clay formation. Specifically, it developed a systematic framework for understanding authigenic clay formation during reverse weathering. Through well-controlled laboratory experiments, the roles of Fe and Al sources, mineral substrates, and solution chemistry were examined in detail. The results shed light on the geochemical triggers, reaction rates, product phases, and mechanisms underlying the formation and transformation of these secondary clays. The key outcomes of this project include geochemical triggers and constraints, reaction rates, and mechanisms of formation and transformation. The laboratory experiments conducted represent one of the most comprehensive investigations of the factors promoting secondary clay formation around diatom biogenic silica in marine sediments. These findings are foundational for understanding the factors regulating elemental sequestration (e.g., Si, C, Fe, Al, Mg, K) in marine environments. Moreover, they highlight the pivotal role of reverse weathering in modulating global climate through CO₂ release. This projects outcomes not only address long-standing questions in the geochemical community but also provide valuable data for future modeling and field investigations. By bridging the gaps in the understanding of authigenic clay formation, this research contributes to resolving the global silicon budget and offers broader implications for climate regulation and biogeochemical cycling. Last Modified: 12/29/2024 Submitted by: YuanzhiTang