Fe sem s 4500 instrument

Using a Hitachi field emission scanning electron microscopy (FE-SEM) S-4500 instrument (Tokyo, Japan), back-scattering electron images were obtained from the thin section coated with carbon. FE-SEM was operated at an emission current of 15 μA and an accelerating voltage of 15 kV. For chemical compositions of mineral phases, energy-dispersive X-ray spectroscopy (EDS) was used according to contrasts of the image corresponding to atomic density.

Back-scattering electron images of thin sections coated with carbon were obtained by field emission scanning electron microscopy (FE-SEM) using a Hitachi FE-SEM S-4500 instrument (Tokyo, Japan) at an accelerating voltage of 15 kV and an emission current of 15 µA. Energy-dispersive X-ray spectroscopy (EDS) was used to analyse chemical compositions of mineral phases according to image contrasts. Micro-Raman spectroscopy with Ion Laser Technology 5500 A (Tokyo, Japan) was used to characterised the fracture/vein-infilling minerals. Raman spectra from fracture/vein-filling minerals were obtained using a 50-cm single polychromator imaging spectrometer (Bruker Optics, Osaka, Japan), which was equipped with an optical microscope (BX51; Olympus), an Ar⁺ laser (514.5 nm, 5,500 A; International Light Technologies, Peabody, MA, USA), and a CCD camera (1024 × 256 pixels; DU401A-BR-DD; Andor Technology, Belfast, Ireland). The incident laser was operated at 20 mW, and the spatial resolution was ~1 μm. An edge-cut filter was used to remove the Rayleigh line. Raman lines of naphthalene at 513.6 cm⁻¹, 763.5 cm⁻¹, 1,021.3 cm⁻¹, 1,147.3 cm⁻¹, 1,382.3 cm⁻¹, 1,464.3 cm⁻¹, and 1,576.3 cm⁻¹ were used to calibrate Raman shift. Spectral resolution was ~1 cm⁻¹. Raman spectra were interpreted based on comparison with those obtained from RRUFF³⁷ (http://rruff.info).