KREEP


KREEP

KREEP, an acronym built from the letters K (the atomic symbol for the element potassium), REE (Rare Earth Elements) and P (for phosphorus), is a geochemical component of some lunar impact melt breccia and basalt rocks. Its most significant feature is its inclusion of a majority of so-called "incompatible" elementsFact|date=March 2008 (those that prefer a liquid state during magma crystallization) and the heat-producing elements potassium, uranium and thorium.

Indirectly, the origin of KREEP is a result of the Moon's origin, which is now commonly believed to be a result of a Mars-sized object that impacted the Earth 4.5 billion years ago (see Giant impact hypothesis). This impact put a large amount of material into circumterrestrial orbit that ultimately reaccreted to form the Moon. Given the large amount of energy that was liberated in this event, it is predicted that a large portion of the Moon would have initially been molten, forming a near-global magma ocean. As crystallization of this magma ocean proceeded, minerals such as olivine and pyroxene would have precipitated and sunk to form the lunar mantle. After crystallization was about three-quarters complete, anorthositic plagioclase would have begun to crystallize, and because of its low density, float, forming an anorthositic crust. Importantly, elements that are incompatible (i.e., those that partion preferentially into the liquid phase) would have been progressively concentrated into the magma as crystallization progressed, forming a "KREEP"-rich magma that initially should have been sandwiched between the crust and mantle. Evidence for this scenario comes from the highly anorthositic composition of the lunar highland crust, as well as the existence of KREEP-rich materials.

Before the Lunar Prospector mission, it was commonly thought that KREEP-rich materials would have formed a near global layer beneath the crust. However, results from the gamma ray spectrometer on this mission show that KREEP-containing rocks are primarily concentrated within the region of Oceanus Procellarum and Mare Imbrium, a unique geological province that is now known as the Procellarum KREEP Terrane. Basins far from this province that excavated deep into the crust (and possibly mantle) such as the Crisium, Orientale, and South Pole-Aitken show only modest, or no, enhancements of KREEP within their rims or ejecta. The enhancement of heat producing elements within the crust (and/or mantle) of the Procellarum KREEP Terrane is almost certainly responsible for the longevity and intensity of mare volcanism on the nearside of the Moon.

ee also

* Lunar mare
* Moon
* Lunar Prospector

References


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External links

* [http://www.psrd.hawaii.edu/Archive/Archive-Moon.html Moon articles in Planetary Science Research Discoveries] , including articles about KREEP


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Look at other dictionaries:

  • KREEP — ist ein magmatisches Gestein, das auf dem Mond vorkommt. Insbesondere wurde es in Form von Impaktbrekzien in Kratern oder neben Basalten (vgl. auch Lunabas und Lunarit) gefunden. Hervorzuheben ist seine chemische Zusammensetzung aus sogenannten… …   Deutsch Wikipedia

  • KREEP — [krēp] n. 〚K (symbol for potassium) + r(are )e(arth) e(lements) + p(hosphorus)〛 a type of basaltic lunar rock rich in potassium, phosphorus, etc. * * * ▪ rock       a suite of lunar lavas, relatively enriched in certain elements, that were… …   Universalium

  • KREEP — es una sigla utilizada para nombrar un tipo de suelo lunar. Cada letra hace referencia a la composición química, así la K es el potasio, y la P corresponde al fósforo. RRE viene del inglés Rare Earth Elements, que quiere decir Elementos Raros de… …   Enciclopedia Universal

  • kreep — [kʀip] n. m. ÉTYM. 1972; mot angl., 1971; de K, symbole du potassium, angl. Rare Earth Element « terre rare », et P, symbole du phosphore. ❖ ♦ Anglic. Substance trouvée sur la Lune, qui contient de grandes quantités de potassium, de phosphore et… …   Encyclopédie Universelle

  • KREEP — [krēp] n. [K (symbol for potassium) + r(are )e(arth) e(lements) + p(hosphorus)] a type of basaltic lunar rock rich in potassium, phosphorus, etc …   English World dictionary

  • KREEP — Se llama KREEP a un tipo de suelo lunar; esta designación proviene de los componentes del mismo: potasio (K), tierras raras (REE, del inglés: Rare earth elements) y fósforo (P). Actualmente se cree que el KREEP representa los últimos restos de la …   Wikipedia Español

  • KREEP — Kalium Rare Erd Elements & Phosphor Bez. f. Teile des Mondgestein, entdeckt durch Apollo 12 …   Acronyms

  • KREEP — Kalium Rare Erd Elements & Phosphor Bez. f. Teile des Mondgestein, entdeckt durch Apollo 12 …   Acronyms von A bis Z

  • KREEP — Potassium, Rare Earth Elements and Phosphorus (Moon Rocks & Soil) Contributor: CASI …   NASA Acronyms

  • KREEP — ˈkrēp noun Etymology: K (potassium) + Rare Englisharth Englishlement + P (phosphorus) : a type of rock found especially on the moon that contains potassium, rare earth elements, and …   Useful english dictionary


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