Nonmagmatic meteorite

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Nonmagmatic meteorite
—  Class  —
Goose Lake meteorite.jpg
Goose Lake Meteorite is an IAB meteorite in the sLL subgroup (low-Au, low-Ni)
Compositional type Iron
Type Iron
Subgroups
Alternative namesNonmagmatic iron meteorites

Nonmagmatic meteorite (also nonmagmatic iron meteorite) is a deprecated term formerly used in meteoritics to describe iron meteorites that were originally thought to have not formed by igneous processes, to differentiate them from the magmatic meteorites, produced by the crystallization of a metal melt. [1] The concept behind this was developed in the 1970s, but it was quickly realized that igneous processes actually play a vital role in the formation of the so-called "nonmagmatic" meteorites. Today, the terms are still sometimes used, but usage is discouraged because of the ambiguous meanings of the terms magmatic and nonmagmatic. The meteorites that were described to be nonmagmatic are now understood to be the product of partial melting and impact events and are grouped with the primitive achondrites and the achondrites. [2]

Contents

Description

Iron meteorites are derived from planetary cores of asteroids and planetesimals. The formation of metallic cores depends on the heat of radionuclides that lead to melting and differentiation into a core and a silicate mantle. While the parent body of the meteorites cools off, the metallic core crystallizes into meteoric iron, an iron-nickel alloy. [1]

In the 1970s, it was realized that some of the iron meteorite groups had properties that were incompatible with this formation mechanism, leading some scientists to posit that they were not formed through this mechanism. [2]

Today, the processes that lead to these unusual properties are described as partial melting and subsequent fast cooling, which prevented melt migration. [3] The most likely cause for this to happen are impact events. [3] [4]

The term "nonmagmatic" is still sometimes used to refer to this grouping of meteorites, although its use is now deprecated. [5]

Subdivision

Three iron meteorite groups are described as being part of the nonmagmatic meteorites. They share a number of similarities, the most easily recognizable is that they contain many silicate inclusions composed of olivine, pyroxene and feldspar. Other iron meteorites can also contain silicate inclusions but with different mineralogy (IVA for example has tridymite and pyroxene). [6] Two of those groups, the IAB and the IIICD meteorites are now classified as primitive achondrites. The IIE meteorites are now classified as regular achondrites. [2]

The following table shows the groups are described as nonmagmatic and their classification:

GroupCurrently classified asCompositional type
IAB Primitive achondrite [2] Iron meteorite
IIICD Primitive achondrite [2] Iron meteorite
IIE Achondrite [2] Iron meteorite

See also

Related Research Articles

<span class="mw-page-title-main">Meteorite classification</span> Systems of grouping meteorites based on shared characteristics

In meteoritics, a meteorite classification system attempts to group similar meteorites and allows scientists to communicate with a standardized terminology when discussing them. Meteorites are classified according to a variety of characteristics, especially mineralogical, petrological, chemical, and isotopic properties.

<span class="mw-page-title-main">Planetary differentiation</span> Astrogeological concept

In planetary science, planetary differentiation is the process by which the chemical elements of a planetary body accumulate in different areas of that body, due to their physical or chemical behavior. The process of planetary differentiation is mediated by partial melting with heat from radioactive isotope decay and planetary accretion. Planetary differentiation has occurred on planets, dwarf planets, the asteroid 4 Vesta, and natural satellites.

<span class="mw-page-title-main">Achondrite</span> Stony meteorite that does not contain chondrules

An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has 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.

<span class="mw-page-title-main">HED meteorite</span> Group of achondrite meteorites

HED meteorites are a clan (subgroup) of achondrite meteorites. HED stands for "howardite–eucrite–diogenite". These achondrites came from a differentiated parent body and experienced extensive igneous processing not much different from the magmatic rocks found on Earth and for this reason they closely resemble terrestrial igneous rocks.

<span class="mw-page-title-main">Iron meteorite</span> Meteorite composed of iron-nickel alloy called meteoric iron

Iron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron meteorites originate from cores of planetesimals, with the exception of the IIE iron meteorite group

In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of magmas produced by igneous differentiation is known as a magma series.

<span class="mw-page-title-main">Fractional crystallization (geology)</span> Process of rock formation

Fractional crystallization, or crystal fractionation, is one of the most important geochemical and physical processes operating within crust and mantle of a rocky planetary body, such as the Earth. It is important in the formation of igneous rocks because it is one of the main processes of magmatic differentiation. Fractional crystallization is also important in the formation of sedimentary evaporite rocks or simply fractional crystallization is the removal of early formed crystals from an Original homogeneous magma so that the crystals are prevented from further reaction with the residual melt.

Magmatic water, also known as juvenile water, is an aqueous phase in equilibrium with minerals that have been dissolved by magma deep within the Earth's crust and is released to the atmosphere during a volcanic eruption. It plays a key role in assessing the crystallization of igneous rocks, particularly silicates, as well as the rheology and evolution of magma chambers. Magma is composed of minerals, crystals and volatiles in varying relative natural abundance. Magmatic differentiation varies significantly based on various factors, most notably the presence of water. An abundance of volatiles within magma chambers decreases viscosity and leads to the formation of minerals bearing halogens, including chloride and hydroxide groups. In addition, the relative abundance of volatiles varies within basaltic, andesitic, and rhyolitic magma chambers, leading to some volcanoes being exceedingly more explosive than others. Magmatic water is practically insoluble in silicate melts but has demonstrated the highest solubility within rhyolitic melts. An abundance of magmatic water has been shown to lead to high-grade deformation, altering the amount of δ18O and δ2H within host rocks.

<span class="mw-page-title-main">Igneous rock</span> Rock formed through the cooling and solidification of magma or lava

Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.

<span class="mw-page-title-main">Primitive achondrite</span> Subdivision of meteorites

Primitive achondrites are a subdivision of meteorites. They are classified on the same rank and lying between chondrites and achondrites. They are called primitive because they are achondrites that have retained much of their original chondritic properties. Very characteristic are relic chondrules and chemical compositions close to the composition of chondrites. These observations are explained as melt residues, partial melting, or extensive recrystallization.

<span class="mw-page-title-main">Lodranite</span> Type of meteorites

Lodranites are a small group of primitive achondrite meteorites that consists of meteoric iron and silicate minerals. Olivine and pyroxene make up most of the silicate minerals. Like all primitive achondrites lodranites share similarities with chondrites and achondrites.

Winonaites are a group of primitive achondrite meteorites. Like all primitive achondrites, winonaites share similarities with chondrites and achondrites. They show signs of metamorphism, partial melting, brecciation and relic chondrules. Their chemical and mineralogical composition lies between H and E chondrites.

<span class="mw-page-title-main">IAB meteorite</span> Group of iron meteorites

IAB meteorites are a group of iron meteorites according to their overall composition and a group of primitive achondrites because of silicate inclusions that show a strong affinity to winonaites and chondrites.

<span class="mw-page-title-main">IIICD meteorite</span>

IIICD meteorites are a group of primitive achondrites. They are classified in a clan together with the IAB meteorites and the winonaites.

<span class="mw-page-title-main">IVB meteorite</span> Type of iron meteorite

IVB meteorites are a group of ataxite iron meteorites classified as achondrites. The IVB group has the most extreme chemical compositions of all iron meteorites, meaning that examples of the group are depleted in volatile elements and enriched in refractory elements compared to other iron meteorites.

IIG meteorites are a group of iron meteorites. The group currently has six members. They are hexahedrites with large amounts of schreibersite. The meteoric iron is composed of kamacite.

<span class="mw-page-title-main">Stony-iron meteorite</span> Meteorites that consist of nearly equal parts of meteoric iron and silicates

Stony-iron meteorites or siderolites are meteorites that consist of nearly equal parts of meteoric iron and silicates. This distinguishes them from the stony meteorites, that are mostly silicates, and the iron meteorites, that are mostly meteoric iron.

This is a glossary of terms used in meteoritics, the science of meteorites.

<span class="mw-page-title-main">IIAB meteorites</span> Type of iron meteorite

IIAB meteorites are a group of iron meteorites. Their structural classification ranges from hexahedrites to octahedrites. IIABs have the lowest concentration of nickel of all iron meteorite groups. Most iron meteorites are derived from the metallic planetary cores of their respective parent bodies, but in the case of the IIABs the metallic magma separated to form not only this meteorite group but also the IIG group.

Bunburra Rockhole is an anomalous basaltic achondritic meteorite. Originally classified as a eucrite, it was thought to belong to a group of meteorites that originated from the asteroid 4 Vesta, but has since been reclassified based on oxygen and chromium isotopic compositions. It was observed to fall on July 21, 2007, 04:43:56 local time, by the Desert Fireball Network (DFN). Two fragments weighing 150g and 174g were recovered by the DFN at 31°21.0′S, 129°11.4′E in the Nullarbor Desert region, South Australia in November of the same year. This is the first meteorite to be recovered using the Desert Fireball Network observatory.

References

  1. 1 2 Chabot, Nancy L.; Saslow, Sarah A.; McDonough, William F.; McCoy, Timothy J. (1 October 2007). "The effect of Ni on element partitioning during iron meteorite crystallization". Meteoritics & Planetary Science. 42 (10): 1735–1750. Bibcode:2007M&PS...42.1735C. CiteSeerX   10.1.1.717.3894 . doi:10.1111/j.1945-5100.2007.tb00534.x.
  2. 1 2 3 4 5 6 M. K. Weisberg; T. J. McCoy, A. N. Krot (2006). "Systematics and Evaluation of Meteorite Classification" (PDF). In D. S. Lauretta; H. Y. McSween (eds.). Meteorites and the early solar system II. Tucson: University of Arizona Press. pp. 19–52. ISBN   978-0816525621 . Retrieved 15 December 2012.
  3. 1 2 Schulz, T.; Upadhyay, D.; Münker, C.; Mezger, K. (30 April 2012). "Formation and exposure history of non-magmatic iron meteorites and winonaites: Clues from Sm and W isotopes". Geochimica et Cosmochimica Acta. 85: 200–212. Bibcode:2012GeCoA..85..200S. doi:10.1016/j.gca.2012.02.012.
  4. ↑ Wasson, J.T; Kallemeyn, G.W (30 June 2002). "the IAB iron-meteorite complex: A group, five subgroups, numerous grouplets, closely related, mainly formed by crystal segregation in rapidly cooling melts". Geochimica et Cosmochimica Acta. 66 (13): 2445–2473. Bibcode:2002GeCoA..66.2445W. doi:10.1016/S0016-7037(02)00848-7. hdl: 2060/20020080608 .
  5. ↑ Qin, Liping; Dauphas, Nicolas; Wadhwa, Meenakshi; Masarik, Jozef; Janney, Philip E. (31 July 2008). "Rapid accretion and differentiation of iron meteorite parent bodies inferred from 182Hf–182W chronometry and thermal modeling". Earth and Planetary Science Letters. 273 (1–2): 94–104. doi:10.1016/j.epsl.2008.06.018.
  6. ↑ Burbine, T. H.; McCoy, T. J.; Meibom, A.; Gladman, B.; Keil, K. (2002). "Meteoritic Parent Bodies: Their Number and Identification" (PDF). In William F. Bottke; Alberto Cellino; Paolo Paolicchi (eds.). Asteroids III. Tucson: University of Arizona press. pp. 653–667. ISBN   978-0816522811 . Retrieved 31 December 2012.
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