Petrological and mineralogical characteristics of mutton-fat obsidian
Modem petrological and mineralogical analytical and testing methods,such as Microzone X-ray diffraction(pXRD),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.
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