Achondrite

Achondrite

An achondrite is a stony meteorite that consists of material similar to terrestrial basalts or plutonic rocks. Compared to the chondrites, they have all been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies. As a result, achondrites have distinct textures and mineralogies indicative of igneous processes.

Achondrites account for about 8% of meteorites overall, and the majority (about two thirds) of them are HED meteorites, originating from the crust of asteroid 4 Vesta. Other types include Martian, Lunar, and several types thought to originate from other as-yet unidentified asteroids. These groups have been determined on the basis of e.g. the Fe/Mn chemical ratio and the 17O/18O oxygen isotope ratios, thought to be characteristic "fingerprints" for each parent body.

Achondrites are classified into the following groups:
* Primitive achondrites (PAC group)
** Acapulcoites
** Lodranites
** Brachinites
** Winonaites
** Ureilites
* Asteroidal achondrites (evolved achondrites)
** HED (Vesta) meteorites
*** Howardites
*** Eucrites
*** Diogenites
*** "Dunite diogenite"
*** "Olivine diogenites"
** Angrites
** Aubrites
* Lunar meteorites (Lunanites)
** Impact breccias
** Lunar Basalts
* Martian meteorites (SNC)
** Shergottites
** Nakhlites
** Chassignites
** OPX martian meteorites (ALH 84001)


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Look at other dictionaries:

  • Achondrite — (aubrite), Cumberland Falls Une acho …   Wikipédia en Français

  • achondrite — n. 1. a stony meteor lacking chondrules. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • achondrite — [ā kän′drīt΄] n. [ A 2 + CHONDRITE] the type of stony meteorite that contains no chondrules achondritic [ā kän′drit′ik] adj …   English World dictionary

  • achondrite — noun Date: circa 1904 a stony meteorite without rounded grains • achondritic adjective …   New Collegiate Dictionary

  • achondrite — achondritic /ay kon drit ik/, adj. /ay kon druyt/, n. a meteorite containing no chondrules. [1900 05; A 6 + CHONDRITE] * * * ▪ meteorite  any stony meteorite containing no chondrules (small, roughly spherical objects that formed in the solar… …   Universalium

  • achondrite — noun Any stony meteorite that contains no chondrules …   Wiktionary

  • achondrite — [ə kɒndrʌɪt] noun a stony meteorite containing no small mineral granules (chondrules) …   English new terms dictionary

  • achondrite — achon·drite …   English syllables

  • achondrite — a•chon•drite [[t]eɪˈkɒn draɪt[/t]] n. astron. a meteorite containing no chondrules • Etymology: 1900–05 a chon•drit′ic ˈdrɪt ɪk adj …   From formal English to slang

  • Achondrite —    A coarsely crystallized stony meteorite containing fragments of various minerals that are large enough to be seen by the naked eye …   The writer's dictionary of science fiction, fantasy, horror and mythology

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