New method for revealing dislocations in garnet: premelting decoration
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Premelting decoration (PMD) of dislocation experiments was carried out on garnets at 1 atmosphere pressure and temperatures of 800–1000 °C. Numerous decorated lines were observed on the polished surface of heat-treated garnet grains. The results of scanning electron microscopy, laser Raman spectroscopy and transmission electron microscopy (TEM) analyses indicate that these decorated lines were generated by premelting reaction along the dislocation lines and subgrain boundaries. The constituents of decorated lines on the polished surface of garnet are hematite, magnetite, and melt. While, in the interior of garnet, their constituents changed to Al-bearing magnetite and melt. The dislocation density of a gem-quality megacrystal garnet grain by means of the PMD is similar to that obtained by TEM, which confirms that the PMD is a new reliable method for revealing dislocations in garnet. This method greatly reduces the cost and time involved in the observation of dislocation microstructures in deformed garnet.
KeywordsGarnet Dislocation decoration Premelting TEM
We are grateful to Prof. David L. Kohlstedt, Editor Larissa F. Dobrzhinetskaya, Reviewers Jun-ichi Ando and Shun-ichiro Karato and Florian Heidelbach for their valuable comments and advice. We thank Mouchun He for his technical assistance in Raman spectroscopy analysis. This work was supported by the National Natural Science Foundation of China (Grant nos. 40872136, 41272224).
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