Pyrometamorphism

Pyrometamorphism is a type of metamorphism in which rocks are changed by heat coming from the fossil fuel fire. The rocks produced by pyrometamorphism include buchite, clinker and paralava, formed due to thermal changes of sedimentary rocks. Both natural and anthropogenic examples of sites with active pyrometamorphism are known. Natural pyrometamorphic rocks are known, e.g., from the Hatrurim Formation. Xenoliths of sedimentary rocks trapped in volcanic lava may undergo pyrometamorphic transformation. Anthropogenic pyrometamorphic rocks are found in burning coal-mining dumps. A great number of minerals, sometimes very rare, are found within these rocks. Of the silicate minerals, the typical ones are especially cordierite, indialite, fayalite, mullite, tridymite and cristobalite (both may be classified as oxide minerals, too), and sekaninaite. Oxide minerals include corundum, hematite, hercynite, magnesioferrite, and magnetite. Some unique minerals typical for meteorites, like oldhamite, are also found in pyrometamorphic rocks.^{[1][2][3][4][5][6]}

Types of pyrometamorphic rocks

The main types of pyrometamorphic rocks are:

• Buchite - usually referring to fused, partially melted rock, often formed in expense of sandstone; it may have both glassy and vesicular texture
• Clinker - it usually refers to fused, not completely melted, shales; typical feature is preservation of the shaly structure
• Paralava (or parabasalt) - a product of complete melting and (partial) recrystallization

Some thermally changed sedimentary rocks are described under a general name: metapelite.

References

1. Grapes, R.H., 2006. Pyrometamorphism. Springer Verlag, Berlin
2. Sokol, E.V., Maksimova, N.V., Nigmatulina, E.N., Sharygin, V.V., and Kalugin, V.M., 2005. Combustion metamorphism. Publishing House of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk (in Russian, with parts in English)
3. Simmons, W.B., Cosca, M.A., Essene, E.J., and Coates, D.A., 1989. Pyrometamorphic rocks associated with naturally burned coal beds, Powder River Basin, Wyoming. American Mineralogist 74, 85-100
4. Grapes, R., Zhang, K., and Peng, Z., 2009. Paralava and clinker products of coal combustion, Yellow River, Shanxi Province, China. Lithos 113(3-4), 831-843
5. Sharygin, V.V., Sokol, E.V., and Belakovskii, D.I., 2009. Fayalite-sekaninaite paralava from the Ravat coal fire (central Tajikistan). Russian Geology and Geophysics 50(8), 703-721
6. Mindat, http://www.mindat.org