2:00 PM - 2:15 PM
[MIS17-02] Recent effort to solve the “dolomite problem”
Keywords:Dolomite, Illite, Carbonate
Dolomite (CaMg(CO3)2) is a thermodynamically stable mineral at room temperature and a common carbonate mineral found in limestone along with calcite and aragonite. While modern seawater is often supersaturated with respect to dolomite, precipitation of dolomite is rarely found in modern environments. Although laboratory synthesis experiments of dolomite have been conducted for several decades, no successful results have been reported, and the precipitation conditions are still being debated. Nonetheless, dolomite is abundant in ancient sedimentary rocks. This paradox has been attracted the interest of many sedimentologists and is known as the "dolomite problem" (Warren, 2000). Because of the uncertainty of precipitation conditions, dolomite is interpreted as a secondary mineral that forms through dolomitization during the early diagenetic stage in the early days. For example, the sabka model, which assumes high-salinity water formed by evaporation, and the mixed-water dolomitization, which considers the difference in saturation index between calcite and dolomite during the mixing of seawater and freshwater, have been proposed.
In the late 1990s, it was shown that microbial activity can lead to primary dolomite precipitation. Since then, synthesis experiments using microbes and studies identifying microbial communities in modern salt lakes where dolomite precipitation occurs have been actively carried out (Vasconcelos et al., 1995). Furthermore, several experimental studies over the past decade have shown that the precipitation of disordered dolomite occurs through inorganic processes. It has been pointed out that the Mg2+ cation forms a hydration layer that inhibits the incorporation into dolomite. Therefore, the addition of catalytic materials, such as dissolved silica and clay minerals, to a solution saturated with dolomite, was tested, and the formation of proto-dolomite was shown (e.g., Liu et al., 2019). In this presentation, the resent progress on the dolomite problem will be discussed. Additionally, our preliminary results from experiments conducted to examine the potential effects of solution concentration and pH on dolomite synthesis catalyzed by clay minerals will be presented.
In the late 1990s, it was shown that microbial activity can lead to primary dolomite precipitation. Since then, synthesis experiments using microbes and studies identifying microbial communities in modern salt lakes where dolomite precipitation occurs have been actively carried out (Vasconcelos et al., 1995). Furthermore, several experimental studies over the past decade have shown that the precipitation of disordered dolomite occurs through inorganic processes. It has been pointed out that the Mg2+ cation forms a hydration layer that inhibits the incorporation into dolomite. Therefore, the addition of catalytic materials, such as dissolved silica and clay minerals, to a solution saturated with dolomite, was tested, and the formation of proto-dolomite was shown (e.g., Liu et al., 2019). In this presentation, the resent progress on the dolomite problem will be discussed. Additionally, our preliminary results from experiments conducted to examine the potential effects of solution concentration and pH on dolomite synthesis catalyzed by clay minerals will be presented.