Thermal decomposition characterization of supergene potassium-jarosite and sodium-jarosite minerals from the northern Tibetan Plateau, China
Lei Chen 1  
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MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
Lei Chen   

MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, NO.26 Baiwanzhuang Street, 115-117, 100037 Beijing, China
Physicochem. Probl. Miner. Process. 2018;54(2):459–466
The thermal decomposition of supergene potassium-jarosite and sodium-jarosite samples from the weathering profiles of sulfide deposits in the northern Tibetan Plateau, China, was investigated. Electron microprobe, scanning electron microscopy, and X-ray diffraction analyses indicated the presence of nearly pure potassium-jarosite and sodium-jarosite. Thermogravimetric analysis of the potassium-jarosite sample revealed mass losses of 11.39 wt% at 443.0 °C, 20.99 wt% at 688.3 °C, and 3.18 wt% at 779.3 °C. The thermogravimetric analysis of sodium-jarosite revealed mass losses of 11.72 wt% at 447.5 °C, 21.32 wt% at 682.6 °C, and 3.70 wt% at 716.5 °C. The results provide no evidence for water-molecule loss below 400 °C, as has been reported previously for natural potassium-jarosite and sodium-jarosite. Thermal-decomposition mechanisms have been proposed for potassium-jarosite and sodium-jarosite based on X-ray diffraction analyses of samples obtained at distinct points along the respective thermal decomposition processes. A comparison of the thermal analysis patterns of potassium-jarosite and sodium-jarosite indicates that sodium-jarosite undergoes the initiation of lattice destruction at a higher temperature.
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