Identification of TiO₂ Polymorphs of the Bauxite Deposit in Central Guangxi by Laser Raman Spectroscopy

Rutile, anatase and brookite are TiO₂ polymorphs. In the rutile in-situ U-Pb dating, rutile was determined primarily on electron microprobe data and cathodoluminescence images, while these methods sometimes could not effectively distinguish rutile, anatase and brookite. If there are a small number of the TiO₂ polymorphs in the sample, the obtained age may be a mixed age with no significant geological significance. Therefore, the identification of TiO₂ polymorphs is very important.

To identify TiO₂ polymorphs from the bauxite deposit in central Guangxi.

TiO₂ minerals in bauxite from central Guangxi were used as the research object, and laser Raman spectroscopy was applied to the identification of TiO₂ isomorphic minerals.

Four groups of laser Raman spectral lines with different characteristics were identified. The first three groups have laser Raman spectral peaks of anatase, rutile and brookite, respectively. The fourth group has two kinds of laser Raman spectral characteristic lines, one has both anatase characteristic peaks of 144, 198, 397, 513, 636cm^-1 and rutile characteristic peaks of 442, 607cm^-1, the other has both anatase characteristic peak of 144cm^-1 and brookite characteristic peak of 153, 247, 325, 636cm^-1.

The TiO₂ polymorphs of the bauxite deposit includs rutile, anatase, brookite and intermediate minerals that undergo phase transformation. The study indicates that the bauxite deposit in central Guangxi may have undergone a later regional metamorphism, leading to the transformation of TiO₂ polymorphs. The laser Raman spectroscopy provides a new method for the identification of TiO₂ polymorphs andrutile for in-situ U-Pb dating.