Metastable growth of corundum adjacent to quartz in a spinel‐bearing quartzite from the Archaean Napier Complex, Antarctica
In a granulite‐facies spinel‐bearing quartzite, corundum, orthopyroxene and sapphirine (and rarely cordierite and sillimanite) form partial rims separating spinel from quartz. Textures indicate the reactions: spinel + quartz = orthopyroxene + corundum, and spinel + quartz = orthopyroxene + sapphirin...
| Published in: | Journal of Metamorphic Geology |
|---|---|
| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
1990
|
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1111/j.1525-1314.1990.tb00459.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1990.tb00459.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1990.tb00459.x |
| Summary: | In a granulite‐facies spinel‐bearing quartzite, corundum, orthopyroxene and sapphirine (and rarely cordierite and sillimanite) form partial rims separating spinel from quartz. Textures indicate the reactions: spinel + quartz = orthopyroxene + corundum, and spinel + quartz = orthopyroxene + sapphirine. Thus, corundum and sapphirine are produced by reactions involving quartz. The low Al‐content of the orthopyroxene (0.5–2.8 wt %) and low values for Mg–Fe distribution coefficient for spinel–sapphirine and spinel–orthopyroxene reflect low‐temperature conditions during formation of the reaction products. Absence of zoning in spinel and a constant Mg–Fe distribution coefficient for spinel–sapphirine and spinel–orthopyroxene, over a compositional range, indicate Mg–Fe equilibration. It is suggested that stable reactions such as spinel + quartz = cordierite or spinel + quartz = garnet + sillimanite were over‐stepped and that metastable reactions give rise to the anomalous juxtaposition of corundum + quartz. |
|---|