Pyrometamorphism is a type of

metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of ...

in which rocks are rapidly changed by heat, ''e.g.'' coming from a rapidly emplaced extrusive or intrusive igneous rock or from a fossil fuel fire. The rocks produced by pyrometamorphism include buchite, clinker and paralava, formed due to melting and/or recrystallisation of sedimentary rocks. Both natural and anthropogenic examples of sites with active pyrometamorphism are known. One well-known area of natural pyrometamorphic rocks is the

Hatrurim Formation The Hatrurim Formation or ''Mottled Zone'' is a geologic formation with outcrops all around the Dead Sea Basin: in the Negev Desert in Israel, in the Judaean Desert on the West Bank, and in western Jordan. It includes late Cretaceous to Eocene ag ...

with outcrops all around the Dead Sea Basin: in the

Negev Desert The Negev or Negeb (; he, הַנֶּגֶב, hanNegév; ar, ٱلنَّقَب, an-Naqab) is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba (pop. ), in the north. At its sout ...

Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...

, in the

Judaean Desert The Judaean Desert or Judean Desert ( he, מִדְבַּר יְהוּדָה, Midbar Yehuda}, both ''Desert of Judah'' or ''Judaean Desert''; ar, صحراء يهودا, Sahraa' Yahuda) is a desert in Palestine and Israel that lies east of Jerus ...

on the

West Bank The West Bank ( ar, الضفة الغربية, translit=aḍ-Ḍiffah al-Ġarbiyyah; he, הגדה המערבית, translit=HaGadah HaMaʽaravit, also referred to by some Israelis as ) is a landlocked territory near the coast of the Mediter ...

, and in western

Jordan Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ' is a country in Western Asia. It is situated at the crossroads of Asia, Africa, and Europe, within the Levant region, on the East Bank of the Jordan Ri ...

Xenolith A xenolith ("foreign rock") is a rock fragment ( country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusively used to describe inclusions in i ...

s of

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particle ...

s trapped in

volcanic lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

may undergo pyrometamorphic transformation, as can some contact wallrocks. Anthropogenic pyrometamorphic rocks are found in burning coal-mining dumps (red shales). A great number of minerals, sometimes very rare, are found within these rocks. Of the silicate minerals, the typical ones are especially

cordierite Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: to . A high-tempera ...

, indialite,

fayalite Fayalite (, commonly abbreviated to Fa) is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system ( space group ''Pbnm'') with cell para ...

mullite Mullite or porcelainite is a rare silicate mineral formed during contact metamorphism of clay minerals. It can form two stoichiometric forms: 3 Al2 O32 SiO2 or 2Al2O3 SiO2. Unusually, mullite has no charge-balancing cations present. As a result, t ...

tridymite Tridymite is a high-temperature polymorph of silica and usually occurs as minute tabular white or colorless pseudo-hexagonal crystals, or scales, in cavities in felsic volcanic rocks. Its chemical formula is Si O2. Tridymite was first described ...

and

cristobalite Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the q ...

(both tridymite and cristobalite may be classified as oxide minerals, too), and

sekaninaite Sekaninaite ((Fe+2,Mg)2Al4Si5O18) is a silicate mineral, the iron-rich analogue of cordierite. It was first described in 1968 for an occurrence in Dolní Bory, Vysočina Region, Moravia, Czech Republic, and is now known also from Ireland, Japan, ...

. Oxide minerals include

corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the ...

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of ...

hercynite Hercynite is a spinel mineral with the formula FeAl2O4. It occurs in high-grade metamorphosed iron rich argillaceous sediments as well as in mafic and ultramafic igneous rocks. Due to its hardness it also is found in placers. It was first descr ...

magnesioferrite Magnesioferrite is a magnesium iron oxide mineral, a member of the magnetite series of spinels. Magnesioferrite crystallizes as black metallic octahedral crystals. It is named after its chemical composition of magnesium and ferric iron. The densi ...

, and

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With ...

. Some rare minerals typical of meteorites, like

oldhamite Oldhamite is a calcium magnesium sulfide mineral with the chemical formula . Ferrous iron may also be present in the mineral resulting in the chemical formula . It is a pale to dark brown accessory mineral in meteorites. It crystallizes in the cub ...

, are also found in pyrometamorphic rocks.Mindat, http://www.mindat.org

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 Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

; 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

Geological processes {{petrology-stub