LI Shan1,2, XI Jiaxin1,2, ZENG Qingjin1, WANG Fuya1,3, LI Kunming4, WEI Jingming1,2,3*
(1. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;
2. University of the Chinese Academy of Sciences, Beijing 100049, China;
3. Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China; 4. Guangzhou Shuiyanxuan Commercial and Trading Co., Ltd, Guangzhou 510370, China)
Abstract: Modern petrological and mineralogical analytical and testing methods, such as Microzone X-ray diffraction (μXRD), X-ray fluorescence spectroscopy (XRF), inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), micro-infrared spectroscopy (MIRO-FTIR), have been applied to systematically study the phase composition, microstructure and chemical composition of the mutton-fat obsidian from an area. The results show that basic characteristics of the mutton-fat obsidian are similar to those of obsidians from other two sources. They are mainly composed of SiO2, Al2O3, K2O, Na2O, belonging to the chemical composition range of rhyolite. These obsidians consist of amorphous glass on a macroscopic basis, with lots of micro-nano sized minerals in the glass. Especially, the mutton-fat obsidian has most abundantly distributed micro-nano sized minerals including potassium nepheline, magnetic hematite and pyrite which are minerals having special chemical properties. This may be the reason why physicochemical properties of the mutton-fat obsidian are obviously superior to those of other two types of obsidian.
Keywords: obsidian; nano-sized mineral; potassium nepheline; magnetic hematite
