It is widely known that post mortem diagenetic alteration processes cause modifications and overprinting of the chemical and isotopic proxies incorporated in vivo in bone apatite and collagen. Understanding the processes occurring during the interaction between fluids and bones in an early diagenetic setting is fundamental to determining the extent to which the commonly-used geochemical proxies in bone get modified during fossilization. The present study experimentally investigates the structural and chemical changes in bone induced by controlled in vitro aqueous alteration experiments under simulated early diagenetic conditions. It is intended to derive a deeper phenomenological and quantitative understanding of the transport and reaction processes that occur in the early stage of fossilization. For this purpose, 3.5 mm-sized cylinders were drilled from modern ostrich cortical bone and immersed in different experimental solutions enriched with tracers such as Zn, Sr, rare earth elements, and U. The experiments ran for several hours to weeks at 30, 60, and 90 °C - the latter two temperatures were chosen to accelerate anticipated early diagenetic modifications of the bone samples. Both the bone samples and the experimental solutions were analyzed using micro-analytical techniques such as Raman spectroscopy, electron microprobe, high-resolution inductively coupled plasma-mass spectrometry, nanoscale ion microprobe, and atom probe tomography to assess mineralogical, chemical, and structural changes from the millimeter to the atomic scale. The results show that element uptake into the bone samples occurs within hours after they have been exposed to an aqueous solution instead of years, as previously assumed. Additionally, distinct modifications of the organic phase were observed, accompanied by the growth of new apatite phases by dissolution-reprecipitation and recrystallization processes. Carbonate-poor or -free hydroxylapatite formed in the sample center and more stable carbonated fluorapatite in the sample rim. From these data, a phenomenological model is derived that explains the interaction between bone and aqueous solutions during the earliest stages of fossilization. This study also demonstrates the importance of using a comprehensive methodological approach when investigating alteration processes whose effects range from the millimeter down to the atomic scale.

众所周知，死后成岩改变过程会导致体内掺入骨磷灰石和胶原蛋白的化学和同位素代用物的修饰和叠印。了解在早期成岩环境中流体和骨骼之间相互作用过程中发生的过程对于确定骨骼中常用的地球化学替代物在石化过程中的改变程度至关重要。本研究通过实验研究体外受控诱导的骨结构和化学变化。模拟早期成岩条件下的水蚀变实验。它旨在对化石化早期发生的运输和反应过程进行更深入的现象学和定量理解。为此，从现代鸵鸟皮质骨中钻出 3.5 毫米大小的圆柱体，并浸入富含 Zn、Sr、稀土元素和 U 等示踪剂的不同实验溶液中。实验在 30、60 时持续数小时至数周。和 90 °C - 选择后两个温度以加速骨样品的预期早期成岩作用。骨样品和实验溶液均使用微量分析技术进行分析，例如拉曼光谱、电子探针、高分辨率电感耦合等离子体质谱、纳米级离子微探针和原子探针断层扫描，用于评估从毫米级到原子级的矿物学、化学和结构变化。结果表明，骨骼样本在暴露于水溶液后数小时内就会吸收元素，而不是之前假设的几年。此外，观察到有机相的明显变化，伴随着溶解-再沉淀和重结晶过程中新磷灰石相的生长。在样品中心形成贫碳酸盐或不含碳酸盐的羟基磷灰石，在样品边缘形成更稳定的碳化氟磷灰石。从这些数据中，导出了一个现象学模型，该模型解释了在化石化的最早阶段骨和水溶液之间的相互作用。