Mineralogical Characteristic of Garnet Containing Sheaf-like Inclusion from Huanggangliang Deposit, Inner Mongolia

There are various types of inclusions in garnet. In this study, garnets containing sheaf-like inclusions from the Huanggangliang deposit, Inner Mongolia, were examined by conventional mineralogical tests, electron microprobe (EPMA), Raman spectrometer, infrared spectrometer (IR), ultraviolet-visible absorption spectrometer, scanning electron microscope (SEM) and X-ray energy spectrometer, to investigate the mineralogical characteristics of these garnet samples and their sheaf-like inclusions. The chemical composition analysis indicated that these garnet samples are andradite, which contain impurity elements including Mn, Ti, Mg and Cr.Raman spectra also indicated that these samples are andradite. Such garnets are dark brown - brown yellow. UV-Vis absorption spectra showed that the electron transition of Fe³⁺ between the energy levels of ⁶A_1g→⁴A_1g ⁴E_g produces a blue-violet absorption peak at 438 nm, which indicates that the colour is mainly caused by Fe^{3 +}. The absorption peak in the IR spectra is related to the vibration of SiO₄^4- and Fe³⁺. The shift of absorption peaks in different samples is caused by the small amount of grossularite and spessartite. The sheaf-like inclusions in the samples are mainly light brown, some are distributed in hexagonal inclusions, others are radial and fan-shaped, and a few are filamentous. The results of SEM indicated that cross sections of the sheaf-like inclusions are mostly approximately circular, rectangular or triangular hollow channels and the longitudinal section is long strip; partly filled with quartz and galena. Al-rich zonation is found in hexagonal inclusions.