Lon clay hill the mineralogy and genesis of enstatite. Enstatite e chondrites are a rare and unusual type of meteorite. Hutson3 1department of physics, university of central florida, 4000 central florida blvd. Concentrations of 26 elements were determined by replicate neutronactivation analysis in 66 ordinary chondrites 22 h, 20 l, 17 ll, 2 intermediate be. Enstatite chondrite an overview sciencedirect topics. They contain a significant amount of nickelbearing iron in the form of small grains that have the same composition and microstructure as the grains in octahedrites. Jan 27, 2017 the earth continues to collect meteorites, the vast majority of which are about as old as our planet. We propose a new model of earths bulk composition based on enstatite chondrites echondrites, the only chondrite group isotopically. There are two types of stony meteorites, chondrites and achondrites. Marks enstatite chondrite, graphite was found showing book.
Chondrite meteorites for sale the meteorite market. It is lower in feo and cao compared to the calculated partial melts of other prospective. This process is experimental and the keywords may be updated as the learning algorithm improves. However, the interrelationship appears to be complex, as the inclusion does not have a smooth. The bulk composition of an average ci carbonaceous chondrite is defined from previous compilations and from the refractory element compositions of different groups of chondrites. Enstatite chondrites contain a variety of unusual minerals that can only form in extremely reducing conditions, including oldhamite cas, niningerite mgs, perryite feni silicide, and alkali sulfides e. The earths remaining bulk accumulated almost purely from enstatitechondrite material. Origin of halogens and nitrogen in enstatite chondrites. Other chondrites other, less common chondrite groups provide important insight into our early solar system history, as well as details on chondrite formation. Unlike most other chondrites, the minerals in enstatite chondrites contain almost no iron oxide. This model allows a quantitative study of accretion and. It alters to serpentine and talc upon the action of hydrothermal solutions.
These meteorites are so heavily altered by water that it is unclear whether they once contained chondrules. They are formed when various types of dust and small grains in the early solar system accreted to form primitive asteroids. We used partial melting experiments of an enstatite chondrite mccoy et al. Chondrite n a type of meteorite containing mineral spheres called chondrules. Rare earth plots and the concentrations of rare earth elements ree in chondritic meteorites randy l. They are by far the most numerous group and comprise about 87% of all finds. All enstatite chondrites are dominantly composed of enstatite rich chondrules plus abundant. Enstatite chondrites for sale e group enstatite chondrites enstatite meteorite e chondrites synonyms. They are named for their primary constituent, chondrules, spherical grains that directly condensed out of the solar nebula and which. The best match with this primitive composition turned. Enstatite chondrites contain a variety of unusual minerals that can only form in extremely reducing conditions, including oldhamite cas, niningerite mgs, perryite feni silicide, and. They are also the driest objects in the solar system. Found in small quantities in eucrites, other calciumrich achondrites, and in the highly reduced e chondrites. Structure, composition, and location of organic matter in.
On one extreme, we find the highly reduced enstatite, or e chondrites that must have formed more closely to the sun than the h, l, or ll chondrites. In sah 97096, we did not find this book shaped graphite but spherulitic or. In particular, we have attempted to ascertain whether any mineralogical differences exist between si3n4 in the ordinary and. The chondrites of this group are named for their primary mineral, enstatite, and they differ in many respects from ordinary and carbonaceous chondrites. Composition of chondrules and matrix and their complementary. Systematics and evaluation of meteorite classification. The ordinary chondrites sometimes called the o chondrites are a class of stony chondritic meteorites.
A second paper in the same issue of nature fischergodde, m. Enstatite mg2si2o6 c 2001 mineral data publishing, version 1. The various chondrite groups likely originated on separate asteroids or groups of related asteroids. Composition and mineralogy of the crustmantle system. The first compilation of chemical composition data for the chondrite groups is the book. Enstatite chondrite density, magnetic susceptibility, and porosity robert j. Enstatite chondrites also known as etype chondrites are a rare form of meteorite thought to comprise only about 2% of the chondrites that fall to earth.
We propose a new model of earths bulk composition based on enstatite chondrites echondrites, the only chondrite group isotopically identical to the earth. For the purposes of this tutorial, we are mostly concerned with meteorite minerals. Mohapatra and murty 2003, leading some workers to suggest that these planets also accreted largely from enstatite chondrite like materials e. The only meteorites classified as chondrites that do not contain chondrules are the ci group. If mercury has a bulk composition as that of enstatite chondrites, the feo content of the surface will be very low. Chondrite project gutenberg selfpublishing ebooks read. Other articles where bronzite chondrite is discussed. The following sets of concentration values have been used in the.
The geochemistry of heds also provides insight into the bulk composition of vesta. Minerals in meteorites 243 correspond to the minerals wollastonite wo, enstatite en, and ferrosilite fs and are reported in terms of molecular percentages e. Enstatite aggregates with niningerite, heideite, and oldhamite 55 with the surrounding enstatite. Enstatite article about enstatite by the free dictionary. Chondrite article about chondrite by the free dictionary. Enstatite is an important rockforming mineral of magnesiumrich magmatic rocks. Compositional relationships between meteorites and terrestrial. Enstatite chondrite density, magnetic susceptibility, and. The mineralogy and genesis of enstatite chondrites. Pdf enstatite chondrites and the composition of the earth. Excluding antarctic and nwa finds, only 24 falls and. The same holds true for the other chondrite groups and they can be placed into a continuous sequence along with the ordinary chondrites. Ck group karoonda chondrites are similar to cvs, but contain far fewer cais, a higher degree of oxidation, and the greatest degree of thermal metamorphism of all carbonaceous chondrites. Composition is essentially fs bulk chemical composition, and oxygen isotopic compositions 4 see below.
Weisberg et al systematics and evaluation of meteorite classification23 fig. Jan 27, 2017 these meteorites are dry and contain grains of metallic ironnickel alloy and iron sulfides set in predominant mgsio 3 the pyroxene enstatite. Excluding antarctic and nwa finds, only 24 falls and finds of e chondrites have been recorded out of the over 2,000 stone meteorites known to date. Bulk chemical composition of soltmany chondrite 33 2 led to the conclusion that, with the exception of iron, the chemical composition of the elements is not. Lunar and planetary science conference in houston, tx, mar 1418,1983. Hypersthene is from the greek words for very strong or.
Bulk composition iron meteorite bulk analysis enstatite chondrite petrologic. A preliminary survey and inquiry utilizing mineral lists at. Pure enstatite without any at all iron is not common, and pure ferrosillite without any magnesium is extremely rare. The principal minerals they contain are olivine, pyroxene, plagioclase feldspar, troilite, and the ironnickel minerals kamacite and taenite. Enstatite chondrites also known as etype chondrites are a rare form of meteorite thought to comprise only about 2% of the chondrites that fall on earth. Most chondrites are believed to originate in the asteroids that orbit the sun between jupiter and mars. Hypersthene is from the greek words for very strong or tough. May 26, 2009 the o and nisotopic bulk compositions of enstatite chondrites are similar to those of earth and mars e. It is colorless, greenish, or yellowish and has a hardness of 5. Righter et al bulk compositions of meteorites and terrestrial planets.
Orthoferrosilite is named for its crystallography and composition. Bulk composition iron meteorite bulk analysis enstatite chondrite petrologic investigation these keywords were added by machine and not by the authors. Part of the minerals and rocks book series minerals, volume 10. A mineral is a naturally occurring chemical compound that has characteristic crystal structure.
Chondrite the most common type of stony meteorite, accounting for 90 percent of all such meteorites. Etype or enstatite chondrites named for their high enstatite mgsio 3 content are extremely reduced. In particular, we have attempted to ascertain whether any mineralogical differences exist between si3n4 in the ordinary and enstatite chondrites, which can be related to distinct contrasts in their isotopic composition described by lee et al. These alphabetical listings include synonyms of accepted mineral names, pronunciation of that name, name origins, and locality information. Orthopyroxene enstatite is the dominant silicate, predominantly clinoenstatite in types 3 mixed with disordered orthoenstatite in subtype 5 and all ordered orthopyroxene in type 6. Some such bodies that are captured in the planets gravity well become the most common type of meteorite by. These meteorites are dry and contain grains of metallic ironnickel alloy and iron sulfides set in predominant mgsio 3 the pyroxene enstatite. As chondrules and matrix have different compositions, mixing of these two components would result in a random bulk chondrite composition.
Chondrites are divided into about 15 distinct groups see meteorites classification on the basis of their mineralogy, 14 bulk chemical composition, and oxygen isotope compositions 15 see below. Enstatite aggregates with niningerite, heideite, and. Pdf chondrules in enstatite chondrites researchgate. One way to increas e the co ratio or reduce h 2 oh 2 is a loss of rock and if condensed ice through gas solid. This model allows a quantitative study of accretion and differentiation processes in the early earth. Chondrite, in general, any stony meteorite characterized by the presence of chondrules. They contain a significant amount of nickelbearing iron in the form of small grains. In previously published articles, the iom from enstatite chondrites was compared to the.
1480 1482 857 937 576 772 704 103 226 1423 116 1277 1204 1211 365 969 1410 1549 1061 845 803 199 597 1155 405 318 1082 1176 1148 739 1018 425 442 1285 658 1156 1429 1352 337 960