Well-Preserved Structure of Silicified Wood: A Case Study from Qitai Silicified Forest, NW China and Its Silicification Mechanisms.

The Qitai silicified wood from Xinjiang, NW China, provides an exceptional archive for investigating the mechanisms of wood silicification. This study applies microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) to characterize the microstructural and mineralogical features of these fossils. The results show that the samples are primarily composed of microcrystalline-macrocrystalline α-quartz having anhedral-euhedral shapes, with minor occurrences of moganite. A well-preserved structure exhibits distinct anatomic details of cellular networks, such as growth rings and rays. Magnified observation revealed that the microcrystalline quartz within cell walls grew outward from the innermost layer of the wall, suggesting silica infiltration from lumina to walls. The opposite growth of elongated columnar quartz within adjacent cell walls terminated at the position of the middle lamellae. Cell lumen infilling exhibits greater variability on filling degree and phase type. The permeation silicification of cell walls and the oligoblastic to polyblastic structure inside cell frameworks contribute to high fidelity preservation. This interpretation helps us understand how the wood structure was perfectly preserved during the silicification, thus emphasizing its significance for wood identification through its preserved structure.