The Mineralogical Characteristics of Cretaceous Albian Glauconite in Zanda, Southwestern Xizang(Tibet) of China and Its Geological Implications
Glauconite as a typical facies mineral is generally regarded as accompanied with transgression sequence, with a low sedimentation rate. Glauconite in the Xiala section from Zanda,southwestern Xizang (Tibet) of China, has been studied by observation under both petrographical microscope and Scanning Electron Microscope(SEM), and the analysis by X-ray Diffractometry(XRD),Fourier Transform Infrared spectroscopy(FTIR), Electron Probe Micro-analysis(EPMA). The above analyses reveal that the glauconites both in sandstone and limestone are highly evolved. The glauconite in sandstone is autochthonous origin, but the glauconite in limestone may come from the underlying glauconitic sandstone. Based on the analysis of sedimentary environment and comparing of glauconitebearing strata with others in adjacent areas, we conclude that the glauconitization in Zanda may be associated with the transgression which caused by final separation of the Indian Continent from the Australian-Antarctic Continent in the Late Albian. Long-term transgressive trend is indicated by the occurrence of the highly evolved glauconite.
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