Intergrowths of corundum and spinel from the Thurein-Taung deposit (Myanmar)

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Abstract

The article displays data on formation conditions and features of unique corundum-spinel aggregates from the Thurein-Taung deposit in Myanmar (Burma). Chemical composition of corundum and spinel is given, and there is traced the effect of iron admixture on the coloring of spinel and parameters of its crystal lattice on the base of X-ray diffraction analysis. The surface of corundum on contact with spinel was studied in detail with aid of the color cathodoluminescence; it is shown that the process of overgrowing by spinel was preceded by resorption of corundum surface. Mineral and fluid inclusions in these minerals have been studied with use of microprobe analysis and the Raman spectroscopy. The temperatures of homogenization have been determined for liquid carbon dioxide in fluid inclusions inside corundum. On the base of mineral equilibria analysis in the Al—Mg—O—CO2—H2S—C system there were determined the optimal activities of magnesium and calcium and the fugacity of carbon dioxide. They are equal to аMg = 10–5; аCa = 10–1 and fCO2 = 10–4. It was found that corundum-spinel aggregates formed at temperature about 400 ºС as a result of partial dissolution of corundum protocrystal by high-temperature solutions containing Mg and Ca. Crystallization of the spinel took place with increasing pH (>3.5) and a decrease of redox potential (Eh ≤ –0.3 V).

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About the authors

A. V. Muromtseva

Institute of Earth Sciences, Saint Petersburg State University

Author for correspondence.
Email: muranna19@gmail.com
Russian Federation, Saint Petersburg

N. I. Ponomareva

Institute of Earth Sciences, Saint Petersburg State University

Email: n_ponomareva@mail.ru
Russian Federation, Saint Petersburg

V. N. Bocharov

Research Park of the Saint Petersburg State University

Email: muranna19@gmail.com
Russian Federation, Saint Petersburg

O. M. Zilicheva

Institute of Geology of Ore Deposits, Petrography,  Mineralogy and Geochemistry RAS

Email: muranna19@gmail.com
Russian Federation, Moscow

References

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Supplementary files

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2. Fig. 1. «Sapphire nodule» (Tureyn-Taung deposite, Myanmar): spinel columnar aggregate overgrowing sapphire (a) or leucosapphire (б).

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3. Fig 2. The location of the Tureyn-Taung deposit in Myanmar (Themelis, 2008).

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4. Fig. 3. The overgrowth of sapphire (a) and leucosapphire (б, в) with columnar aggregates of variously colored spinel. Marking the border of minerals when spinel is filled with cracks and irregularities on the surface of corundum (г).

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5. Fig. 4. Color cathodoluminescence of corundum and spinel after exposure to the sample with an electron beam: excited corundum of bright red color; black field is spinel. Yellow circles outlines the mineral phases between corundum and spinel. Image field width — is equal 300 microns.

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6. Fig. 5. Graphite plate (1) facing the surface of the spinel (2) and oriented perpendicular to the plane of the polished plate.

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7. Fig. 6. Mineral inclusions in corundum: magnesite (1) and calcite (2).

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8. Fig. 7. Numerous inclusions of graphite in spinel near the border with corundum (in transmitted light).

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9. Fig. 8. Primary liquid-gas inclusions in corundum.

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10. Fig. 9. Stability fields of spinel, graphite, corundum, ye’elimite, calcite and andhydrite at a temperature of 400 °C and component activities: аMg2+ = 10–5, аCa2+ = 10–1, fCO2 = 10–4. The legend is given in table 4.

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