Chemical composition in phosphate materials from the ocean floor@en

Content, distribution patterns, and speciation of Cl in phosphorites and bone phosphate from the ocean floor, as well as in a set of samples from the land are studied. Total Cl content varies from 0.05 to 4.25% in phosphorites and from 2.48 to 2.75% in recent phosphate-bearing sediments. Recent phosphorites are enriched in Cl relative to ancient ones. Bound Cl content (not extractable by washing), which increases with lithification, varies from 0.17 to 0.60% in ocean and land phosphorites and from 0.02% to 1.30% in bone phosphate. Na content in most samples is higher relative to Na of NaCl due to its incorporation into the crystal lattice of apatite. However, the opposite relationship is observed in some samples indicating partial Cl incorporation into the anion complex of phosphate. Behavior of Cl in phosphorites from the present-day ocean floor is controlled by early diagenetic processes, whereas the role of weathering, catagenesis, and hydrogeological factors may be crucial for phosphorites on continents.本研究系统探究了海底磷灰岩、骨磷酸盐以及一组陆地样品中氯（Cl）的含量、分布模式与赋存形态。磷灰岩的总氯含量介于0.05%至4.25%之间，现代含磷酸盐沉积物的总氯含量则为2.48%至2.75%。相较于古磷灰岩，现代磷灰岩的氯元素富集程度更高。无法通过水洗提取的结合态氯含量随岩化作用增强而升高，海底与陆地磷灰岩中的该类氯含量范围为0.17%至0.60%，骨磷酸盐中的含量区间为0.02%至1.30%。多数样品中的钠（Na）含量高于氯化钠（NaCl）中的钠含量，这源于钠掺入了磷灰石的晶格结构中；但部分样品呈现相反的规律，表明氯元素部分掺入了磷酸盐的阴离子络合物内。现代海底磷灰岩中氯的地球化学行为受早期成岩作用调控，而风化作用、后生成岩作用与水文地质因素对大陆磷灰岩的演化可能起到关键控制作用。