Mugearite () is a type of oligoclase-bearing

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

, comprising

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

, and opaque oxides. The main

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

in mugearite is oligoclase. Mugearite is a

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

-rich member of the

alkaline magma series The alkaline magma series is a chemically distinct range of magma compositions that describes the evolution of an Alkaline volcanic rock, alkaline mafic magma into a more evolved, silica-rich end member. Geochemical characterization Rocks in t ...

. In the

TAS classification TAS stands for Total Alkali Silica. The TAS classification can be used to assign names to many common types of volcanic rocks based upon the relationships between the combined alkali and silica contents. These chemical parameters are useful because ...

of volcanic rock, mugearite is classified as sodium-rich basaltic trachyandesite.

Examples

Western Scotland

Mugearite was first identified at Mugeary on the island of Skye, Scotland by

Alfred Harker Alfred Harker Fellow of the Royal Society, FRS (19 February 1859 – 28 July 1939) was an English geologist who specialised in petrology and interpretive petrography. He was lecturer in petrology at the University of Cambridge for many years, a ...

in 1904.

Outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s of mugearite also occur on the island of Mull. These examples of mugearite were formed during a period of continental

flood basalt A flood basalt (or plateau basalt) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot (geolo ...

volcanic activity that happened in western Scotland during the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

period of the Earth's geological history, when the North Atlantic Ocean opened between Europe and North America.

Oceanic islands

Mugearite has been erupted by the volcanoes of some oceanic islands at hotspots. Examples are

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the Atlantic Ocean, South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overs ...

, Saint Helena,

Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...

Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...

and

Tahiti Tahiti (; Tahitian language, Tahitian , ; ) is the largest island of the Windward Islands (Society Islands), Windward group of the Society Islands in French Polynesia, an overseas collectivity of France. It is located in the central part of t ...

Mars

Analysis of a Martian rock found by the ''Curiosity'' rover and named "Jake Matijevic" (or "Jake M"), after a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

engineer, determined that this Martian rock is very similar to mugearite erupted on Earth.

References

I. D. Muir and C. E. Tilley, ''Mugearites and Their Place in Alkali Igneous Rock Series,'' The Journal of Geology, Vol. 69, No. 2 (Mar., 1961), pp. 186-203
Aphanitic rocks Basalt {{Volcanology-stub