Bulk chemical composition of soltmany ordinary chondrite. The authors observe a sample size of 35 asteroids and find 6 of these had spectra similar to apollo 1862 and may share its qclass a. We thank the organizers of this book and the insightful workshop at the. Although, as mentioned above, simsbased analyses of ordinary chondrite chondrule silicates have already been reported alexander, 1994, jones and layne, 1997, ruzicka et al. Pentlandite can be formed in chondrite by different means 1, 10. They are by far the most numerous group and comprise about 87% of all finds. Low temperature magnetic transition of chromite in. However, the h4 chondrite shows a welldefined positive correlation, confirming similar observations on other h chondrites 5. The following sets of concentration values have been used in the geochemical literature for the purpose of preparing plots of chondritenormalized concentrations of ree against atomic number or inverse ionic radius. Ordinary chondrites are probably rare in the main part of the asteroid belt meibom and clark, 1999. Oxygen isotopic compositions of chondrules in allende and. Ordinary chondrites from the meteorites australia collection.
Formation of metal in gro 95551 and comparison to ordinary. The ordinary chondrites sometimes called the o chondrites are a class of stony chondritic meteorites. Chondrites are grouped according to their petrological type texture, crystal structure, etc. A prepared end section of the ordinary chondrite northwest africa 869 l46, found tindouf, algeria, 2000 displays a wealth of colorful grainlike chondrules and multiple tiny flakes of extraterrestrial nickeliron. Some such bodies that are captured in the planets gravity well become the most common type of meteorite by. Future work may 1 explain the correlation between an objects size and composition that is observed in the h peak see appendix a. Trace element geochemistry of ordinary chondrite chondrules. Part of the astrophysics and space science library book series assl, volume 445. As chondrules and matrix have different compositions, mixing of these two.
By continuing to browse this site you agree to us using cookies as described in. First recorded find of ordinary chondrite material in the. Ordinary chondrite an overview sciencedirect topics. Although all chondrite compositions can be considered primitive, there is variation among the different groups, as discussed above. For example, chondrules in carbonaceous chondrites typically have. Small, systematic textural differences among the ordinary chondrite groups are observed for metal abundances and chondrule size table 2. Most commonly found in shocked plagioc lasebearing shergottites and ordinary chondrites. Meteorites australia collection ordinary chondrites. Composition of chondrules and matrix and their complementary. In terms of mineralogy, ordinary chondrites are primarily composed of olivine, orthopyroxene, and a certain percentage of more or. Their olivine is more ferich than in the other ordinary chondrites fa2732, implying that.
The selected ordinary chondrites cover all petrologic types 3 to 6, as defined by van schmus and wood 1967. Ll chondrites have low total iron and low metal contents 35% feni alloys by mass, of which 2% is metallic fe. Chondrules and ordinary chondrites discussion summary. The first compilation of chemical composition data for the chondrite groups is the book.
Graphitemagnetite aggregates in ordinary chondritic. There is a hiatus between enstatite chondrites and ordinary chondrites and also between the ordinary h and l chondrites. The absorption spectra are composites of the 2line patterns of olivine mg, fe 2 sio 4 and pyroxene mg, fesio 3 and the 6line patterns of troilite fes and kamacite nickeliron alloy with bodycentered cubic structure. One surface has been sawed and polished, revealing the internal structure. They are named for their primary constituent, chondrules, spherical grains that directly condensed out of the solar nebula and which underwent one or more heating and cooling cycles. The principal minerals they contain are olivine, pyroxene, plagioclase feldspar, troilite, and the ironnickel minerals kamacite and taenite. Carbonaceous chondrites are subdivided into six well. The most extensively metasomatized ordinary chondrite is tieschitz h3. This is most apparent in the ordinary l chondrites which exhibit a metal deficiency of. Quick navtop about ordinary chondrite meteorite classification subdivisions synonyms internet links recorded finds locality list mineral andor locality is an outreach project of the hudson institute of mineralogy, a 501c3 notforprofit organization.
If the majority of those neos would be of ordinary chondritic composition this would of course result in a higher percentage of ordinary chondrite falls. Lunar meteorites moon rocks, mars meteorites and other rare types. They comprise about 3 percent of all meteorite s collected after being seen to fall to earth. Systematics and evaluation of meteorite classification lunar and. Chondrites of this clan are designated as ordinary just because they are the most common class of stony meteorites, representing more than 85% of all witnessed chondrite falls. On a plot of cobalt concentration in kamacite versus fa content in olivine, there is a hiatus between h and l, but no hiatus between l and ll chondrites figure 15. Weisberg et al systematics and evaluation of meteorite classification23 fig.
About 46% of ordinary chondrite falls belong to this group, which makes them the most common type of meteorite to fall to earth. Bulk compositions, classification, lithophileelement fractionations and compositionpetrographic type relationships. The ankober meteorite, a stony meteorite classified as an ordinary chondrite, which fell in ethiopia in 1942. Aggregates consisting largely of submicrometre graphite and magnetite crystals have been identified in 14 unequilibrated and regolith breccia, ordinary chondrites. The ordinary chondrites are thought to have originated from three parent asteroids, with the fragments making up the h chondrite, l chondrite and ll chondrite groups respectively. However, perhaps most surprising are the ordinary and r chondrite compositionsthe ordinary chondrite composition is similar to that of most comets, as well as enceladus, while the r chondrite composition is more denriched than any measured comet. Although fewer than 100 carbonaceous chondrites are known, accounting for only about 5% of chondrite falls, they provide a great deal of information about the origin of the sun and planets, and. Chondrites are the commonest kind of meteorite, accounting for about 86% of falls, and, because they come from asteroids that never melted or underwent differentiation, have, except for the. Taken at face value, this would seem to imply that the ordinary and r chondrites formed further. Systematics and evaluation of meteorite classification. The isotopic composition of the higher petrologic types 46 is lighter in the range. Bulk density measurements of 11 pieces of one fall, pultusk h group, were also. If the oc chondrules mixing line in the oxygen 3isotope diagram formed by the interaction of. Carbonaceous chondrite, a diverse class of chondrite s one of the two divisions of stony meteorite s, important because of the insights they provide into the early history of the solar system.
Gro 95551 represents a new chondrite type with chemical affinity to the ordinary chondrites. H6 chondrite in pl showing a recrystallized ordinary chondrite in which the primary texture has been essentially destroyed and chon drule boundaries are not easily discernable. Variations of ni content in pentlandite from a matrix of ordinary chondrite as a function of the group of ordinary chondrite h, l, ll. A chondrite is a type of stony meteorite made mostly of iron and magnesiumbearing silicate minerals that have remained little changed from the dawn of the solar system, over 4.
The variable carbon isotopic composition of type 3. Furthermore, there has been an additional independent fractionation of metal with respect to silicates both within and between groups. For the first time, ordinary chondrite materialthe most common type among the presentday fall meteoritehas been found in the unique kaidun breccia. Individual chondrules are thought to have formed in distinctive locations within the solar nebula, but a chondrite typically contains a mix of chondrites. The following sets of concentration values have been used in the geochemical literature for the purpose of preparing plots of chondrite normalized concentrations of ree against atomic number or inverse ionic radius. Ubiquitous chondritic solids tracking the evolution of. Chondrites are comprised mostly of fe and mgbearing silicate minerals found in both chondrules and fine grained matrix, free feni metal found in various states like large blebs, small grains andor even chondrule rims, and various refractory inclusions such as caalrich inclusions cais found in many carbonaceous. Bruderheim is the most massive of 16 witnessed and confirmed meteorite falls to have been recovered from canada and one of 3 witnessed canadian l6 falls. A number of taxonomic parameters are used to resolve the individual ordinary chondrite groups. Potassium isotope compositions of carbonaceous and. The ninormalized bulk metal composition of gro 95551 is refractorydepleted and volatilerich relative to bencubbin and related metalrich chondrites, but bears strong similarities to equilibrated ordinary chondrite metal. Oxygenisotope compositions of cais and amoeboid olivine aggregates. The formation and evolution of ordinary chondrite parent.
Canadian institute for theoretical astrophysics, 60 st george street, toronto, on, m5s 3h8, canada. The ordinary chondrites are a class of stony chondritic meteorites. Ci chondrites seem to be nearly identical in composition to the sun for all but the gasforming elements e. On the basis of abundance of siderophile elements and compositions of olivine and kamacite figure 15. Chondrules in cv, cr and ordinary chondrites are typically. The fact that the chondrite allende, with the oldest chondrules, is a representative of the class of chondrites cv having the largest content of cais, which were created and distributed very early in nebular history section 1, is con. We classified thirtyfive h, twentyseven l, and fourteen ll chondrites according to their degree of shock meta morphism.
A survey of bulk carbon isotopic compositions has been carried out for a suite of h, l, and ll ordinary chondrites, from the most unequilibrated type 3 to the metamorphosed type 6. If, for example, the dust were of ordinary chondrite composition, it would contain 27% of the total o, 0. A carbonaceous chondrite is a rare type of stony meteorite which contains large amounts of the magnesiumrich minerals olivine and serpentine and a variety of organic compounds, including amino acids. Chondrite meteorites are the most common accounting for 83. Compared to the bulk composition of our solar system, represented by the solar photosphere and ci chondrites palme et al. The bulk densities of 82 samples of 72 ordinary chondrites ocs were measured to an accuracy of. Only 1 in 10 ordinary chondrite falls belong to this group. Rare earth plots and the concentrations of rare earth elements ree in chondritic meteorites randy l. Ordinary chondrites ordinary chondrites are extraterrestrial rocks containing chondrules and a matrix of minerals including iron and nickel combinations and any number of mineral combinations.
Extreme oxygenisotope compositions in magnetite from. Ordinary chondrites ocs are by far the most abundant meteorites 80% of all falls. Although significant progress has been made since the asteroid iii book in. If it were of c1 chondrite composition, it would contain 55% of the o, 11% of the c, and 190 ppm of the h.
The discovered object is a large unequilibrated olivinepyroxene porphyritic chondrule, with peripheral and central zones of different structures, suggesting different crystallization regimes. Maskelynite na,casi,al 3 o 8 has the composition of plagioclase and has been transformed into a glass by shock metamorphism. Shock metamorphism of ordinary chondrite meteorites article pdf available in geochimica et cosmochimica acta 5512. The l group of ordinary chondrites account for roughly 40% of all meteorite falls. Primitive meteorites such as the unequilibrated ordinary chondrites have undergone only minor thermal processing on their parent asteroids, and thus provide relatively unaltered isotopic records. Many, many stone meteorites from various classifications. L chondrites have low total iron contents including 711% feni metal by mass. Ll chondrites have low total iron and low metal contents 35% feni metal by mass. They are formed when various types of dust and small grains in the early solar system accreted to form primitive asteroids. Thus, ordinary chondrites might be not that ordinary at all. Pdf shock metamorphism of ordinary chondrite meteorites. Chondrules are the basic building blocks of chondrites.
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