Apatite, Magnesian Calcite, and Silica: An Experimental Approach to their Reactivity in Natural Environments

磷灰石、镁方解石和硅石，沿着 粘土是海洋沉积物中最丰富的相。 知识 镁方解石的物理和化学性质是 如果我们要了解它们的生物生产， 碳酸盐胶结物在海洋环境中的作用 地球二氧化碳收支中的镁方解石及其命运 在成岩作用期间。 磷灰石的稳定性和反应速率 由于磷灰石在环境中的重要性， 磷的沉积循环，在磷块岩的形成过程中 沉积物，并控制海洋的肥力。 二氧化硅的稳定性和反应速率数据将有助于解释 二氧化硅在成岩作用期间经历的一系列改性， 并有助于确定二氧化硅在沉积循环中的作用。 不幸的是，以前在这些系统中的调查 未能产生普遍接受的模型， 稳定性，部分原因是使用的材料不足 稳定性和动力学实验。 对化学和固溶体的透彻理解 合成样品的性质是必要的， 并可评价自然相的溶解行为。 我们 方法是比较同质的，良好的， 将合成相结晶为天然材料。 我们将 将我们以前对镁方解石的测量扩展到 天然样品的组成范围。 我们还将扩大 我们合成的磷灰石和蛋白石。 稳定性测定将 在整个温度范围内进行， 成岩条件 SEM、X射线、电子探针、拉曼、 合成和天然样品的红外分析将 提供了解释溶液行为的基础 这些矿物质，以及它们在自然界中的反应， 环境

Apatite, magnesian calcite, and silica are, along with clays, the most abundant phases in marine sediments. Knowledge of the physical and chemical properties of magnesian calcites is necessary if we are to understand their biogenic production, the carbonate cements in the marine environment, the role of magnesian calcites in the CO2 budget of the earth, and their fate during diagenesis. Apatite stabilities and reaction rates in solution are needed because of the importance of apatite in the sedimentary cycle of phosphorus, in the formation of phosphorite deposits, and in controlling the fertility of the ocean. Stability and reaction rate data on silica will help to explain the series of modifications silica undergoes during diagenesis, and help to define the role of silica in the sedimentary cycle. Unfortunately, previous investigations in these systems have failed to produce universally accepted models of their stabilities, partly because of the inadequacy of materials used in stability and kinetic experiments. A thorough understanding of the chemistry and solid solution nature of synthetic samples is necessary before the stabilities and solution behavior of natural phases can be evaluated. Our approach is to compare the characteristics of homogeneous, well- crystallized synthetic phases to natural materials. We will extend our previous measurements on magnesian calcites to span the composition range of natural samples. We will also extend our syntheses to apatite and opal. Stability determinations will be made throughout a temperature range corresponding to diagenetic conditions. SEM, x-ray, electron microprobe, Raman, and IR analyses of both synthetic and natural samples will provide a basis for interpretation of the solution behavior of these minerals, and thus their reactions in the natural environment.