Short-wavelength infrared spectroscopy and EPMA of white mica from Baiyanghe uranium district in Xinjiang
Uranium is one of the critical metals in China,and it is of great significance to the development of science and technology and national security.The Baiyanghe uranium deposit is an important hydrothermal uranium deposit,and white mica is widely developed in the process of uranium mineralization.Studies have shown that the shortwave infrared spectra of white mica contain rich geological information,recording its formation environment and its relationship with mineralization,however,systematical variation rules to shortwave infrared spectral parameters of white mica and geological influencing factors are still poorly known.In this paper,we use shortwave infrared spectroscopy and electron probe analysis to study the white mica from Baiyanghe uranium deposit.The results indicate that white mica with Al-OH absorption wavelengths from the Baiyanghe uranium deposit range from 2 190 nm to 2 220 nm,and the geochemical compositions indicate an obvious Tschermak substitution in white mica and suggest that variations in the Al-OH wavelengths of white mica are mainly affected by the Fe and Mg content and Fe/(Fe + Mg)ratios in addition to the wall rock composition.The white mica exhibiting a shorter Al-OH absorption wavelength indicates a relatively high-temperature hydrothermal environment,while the white mica with a longer Al-OH absorption wavelength suggests a relatively low-temperature hydrothermal environment.In addition,it is found that the white micas close to the uranium mineralization in the Baiyanghe uranium deposit,have shorter Al-OH wavelengths,greater ISM values,and lower FWHM 2 200 values than those with features unlike those near the uranium mineralization.The spatial distributions and variations in the Al-OH wavelengths,ISM values,and FWHM 2 200 values for white mica suggest that a hydrothermal mineralization center may be located in the northern contact zone between the Yangzhuang granite porphyry and the Devonian intermediate-acid volcanic rocks of the Baiyanghe uranium deposit.This study is of great practical significance for improving the genesis and for deep and peripheral exploration in Baiyanghe uranium deposit,and also has important reference value for the exploration of other hydrothermal metal minerals.
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