近日，美国弗吉尼亚理工大学Shuhai Xiao团队研究了磷灰石纳米晶体上的无定形二氧化硅涂层在保存埃迪卡拉纪多塞汉托组磷化胚胎样微化石中的作用。相关论文于2025年8月14日发表在《地质学》杂志上。

埃迪卡拉纪多塞汉托组（600 Ma）以其保存完好的磷化微化石而闻名，其中包括被解释为后生动物胚胎的球形结构。为了保持这种精细的细胞和细胞内结构，磷灰石纳米晶体的稳定性对溶解和再结晶至关重要。一旦保存下来，这些结构就会显示出纳米晶体所定义的细节水平，在高分辨率图像中类似于精细像素。然而，人们对这些微化石中磷灰石纳米晶体稳定性的机制尚不清楚。

研究组利用高分辨率透射电子显微镜（HRTEM）研究了这些化石胚胎中磷灰石纳米晶体的纳米尺度特征，以阐明其显著保存的机制。x射线衍射和Rietveld细化证实了化石是由结晶氟磷灰石组成的。HRTEM成像显示，化石胚胎由有序排列的微拉长的氟磷灰石纳米晶体组成，通常为~90 nm宽，~180 nm长。一个关键的发现是存在一层薄的（~ 1nm），无定形二氧化硅的保形涂层，与氟磷灰石纳米晶体的晶体学方面密切相关。

在成岩作用和低温蚀变过程中，二氧化硅护套有助于保护纳米晶体不发生再结晶，并有可能提高结构稳定性，从而有助于胚胎的长期保存。因此，这些纳米晶体不受溶解或再结晶过度生长的影响，在磷化微化石中保持了精细的“像素”大小。这些发现为研究化石保存异常的过程提供了有价值的见解，为未来研究早期动物进化和保存地质记录中微妙的生物结构铺平了道路。

附：英文原文

Title: The role of amorphous silica coating on apatite nanocrystals in the exceptional preservation of phosphatized embryo-like microfossils from the Ediacaran Doushantuo Formation

Author: Seungyeol Lee, Huifang Xu, Shuhai Xiao

Issue&Volume: 2025-08-14

Abstract: The Ediacaran Doushantuo Formation (ca. 600 Ma) in South China is renowned for its exceptionally preserved phosphatized microfossils, including globular structures interpreted as metazoan embryos. To preserve such fine cellular and intracellular structures, the stability of apatite nanocrystals against dissolution and recrystallization is essential. Once preserved, these structures exhibit a level of detail defined by the nanocrystals, analogous to fine pixels in a high-resolution image. However, the mechanisms responsible for the stability of apatite nanocrystals in these microfossils are still unknown. This study investigates the nanoscale features of apatite nanocrystals in these fossilized embryos using high-resolution transmission electron microscopy (HRTEM) to elucidate the mechanisms responsible for their remarkable preservation. X-ray diffraction and Rietveld refinement confirmed that the fossils are composed of crystalline fluorapatite. HRTEM imaging revealed that the fossilized embryos consist of ordered arrays of slightly elongated fluorapatite nanocrystals, typically measuring ～90 nm in width and ～180 nm in length. A key finding is the presence of a thin (～1 nm), conformal coating of amorphous silica intimately associated with crystallographic facets of the fluorapatite nanocrystals. The silica sheathing may have contributed to the long-term preservation of the embryos by helping to protect the nanocrystals from recrystallization and potentially enhancing structural stability during processes such as diagenesis and low-temperature alteration. Thus, these nanocrystals are insulated from dissolution or recrystallization overgrowth, maintaining the fine “pixel” size in phosphatized microfossils. These findings offer valuable insights into the processes responsible for exceptional fossil preservation, paving the way for future research on early animal evolution and the preservation of delicate biological structures in the geological record.

DOI: 10.1130/G53415.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53415.1/660561/The-role-of-amorphous-silica-coating-on-apatite