MINERALOGICAL CHARACTERISTICS OF SILICIFIED WOOD IN YANQING DISTRICT OF BEIJING

The mineralogical characteristics of silicified wood in Yanqing are analyzed by the test methods of X-ray fluorescence (XRF), infrared spectroscopy (IR) and X-ray diffraction (XRD). The results show that the samples of silicified wood of two different plant species but formed in the same burial site are of similar origin, and their colors are closely related to the types and contents of elements in the silicified wood. The XRD analysis indicates that the main compositions of silicified wood with different colors and plant species are consistent, i.e. SiO₂, with small traces of other minerals. The infrared absorption bands of the two silicified wood specimens are basically the same, showing typical quartzite jade infrared absorption spectrum and containing a small amount of adsorbed water. The main mineral composition of the two specimens are cryptocrystalline quartz under the polarized microscope. The sedimentary environment of silicified wood in Tuchengzi Formation of Yanqing was shallow lacustrine deposit in semiarid-semihumid climate, accompanied by volcanic activity.