Achondrites stony meteorites

Eucrites are achondritic stony meteorites that originate from the surface of the asteroid 4 Vesta. Die meteorite Serra de Mag6, an eucrite, contains quartz veinlets. They are identical to crack-seaT quartz veinlets in terrestrial rocks, and are extraterrestrial and ancient because they pre-date a 4.40 Ga metamorphism. The quartz was likely deposited from liquid water solutions (as are terrestrial veins). Because there is no indication of internal (magmatic) water in the eucrite meteorites and thus in Vesta, the water from which the veinlet was deposited probably came from outside Vesta. By analogy with water ice deposits on the Moon and Mercury, Vesta and similar asteroids may have had (or now have) polar ice deposits, possibly remainders from comet impacts (Treiman et al., 2004 [339]). 

Chondrites Achondrites Stony iron meteorites Iron meteorites... 

The largest class of meteorite finds is stony meteorites, made principally of stone. The general stony classification is divided into three subclasses called chondrites, carbonaceous chondrites and achondrites, and it is at this level of distinction at which we will stop. Before looking at their mineral and isotopic structure in more detail, it is useful to hold the composition of the Earth s crust in mind here for comparison. The Earth s crust is 49 per cent oxygen, 26 per cent silicon, 7.5 per cent aluminium, 4.7 per cent iron, 3.4 per cent calcium, 2.6 per cent sodium, 2.4 per cent potassium and 1.9 per cent magnesium, which must have formed from the common origin of the solar system. 

Fig. 10.1. Rb-Sr isochrone measured from separated components of the stony meteorite Guarena. The initial 87Sr/86Sr ratio is slightly higher than that inferred in basaltic achondrites (BABI) because of a period of metamorphism. After Wasserburg, Papanastassiou and Sanz (1969), with permission. Courtesy G.J. Wasserburg.

Stone meteorite A meteorite largely consisting of silicate minerals. Stony meteorites are divided into achondrite and chondrite varieties. 

Achondrites are rare stony meteorites that have few or no chondrules. These rocks may be chunks of the crusts of larger bodies, such as other planets. Meteorites that originated on the Moon and Mars fall into this category. 

Achondrites as a whole show one curious property when compared to the total range of meteorite types—chondrites, achondrites, stony irons, and irons. Many of the achondrite types... 

There is a wide range of meteorite types, which are readily divided into three main groups the irons, the stony irons and the stones (see also Volume 1 of the Treatise). With this simple classification, we obtain our first insights into planetary dilferentiation. All stony irons and irons are differentiated meteorites. Most stony meteorites are chondrites, undifferentiated meteorites, although lesser amounts are achondrites, differentiated stony meteorites. The achondrites make up —4% of all meteorites, and <5% of the stony meteorites. A planetary bulk composition is analogous to that of a chondrite, and the differentiated portions of a planet—the core, mantle, and crust— have compositional analogues in the irons, stony irons (for core-mantle boundary regions), and achondrites (for mantle and crust). 

Types of meteorite Meteorites may be subdivided into two main categories - unmelted meteorites, that is those which come from a parent body which has not been fractionated since its aggregation early in the history of the solar system, and melted, or differentiated meteorites (Fig. 2.8). Unmelted meteorites are stony meteorites, the chondrites, and are made up of the same silicate minerals that are found on Earth. Melted meteorites are of three types. They include some stony meteorites (the achondrites), the iron meteorites, whose composition is dominated by a metallic iron-nickel alloy, and stony-iron meteorites, meteorites which are made up of approximately equal proportions of... 

Notice that meteorites are classified first of all into three large categories stony, iron, and stony-iron. As their name suggests, stony meteorites are similar in appearance and chemical composition to rocks found on the Earth s surface. Stony meteorites are divided into two major categories chondrites and achondrites. Chondrites are stony meteorites that contain small spheres, called chondrules, with diameters of about 1 mm, consisting of minerals that were once melted and that have now aggregated to form the meteorite. Stony meteorites lacking chondrules are called achondrites. 

Meteorites are grouped into three major classes irons, stones and stony-irons. Based on compositional dissimilarities, stony meteorites are subdivided into chondrites and achondrites. Chondrites are the most primitive meteorites based on their near-solar volatile composition and radiometric ages of 4.566 billion years, reflecting their formation during, or shortly after, the birth of the Solar System (5). Within the chondrites, there exists a carbonaceous subclass that contains up to 3 weight-% of organic carbon, a characteristic that contributes to a generally dark appearance. Carbonaceous chondrites themselves are subdivided into CM, Cl, CV and other classes based on a combination of their... 

The so-called stony meteorites include chondrites (carbonaceous and ordinary), as well as achondrites and the rare undifferentiated nonchondrites. Stony meteorites make up 94.2% of all falls, whereas irons (4.5%) and stony irons (1.2%) make up the rest. The undifferentiated nonchondrites and the martian and lunar meteorites are rare and have never been observed to fall. 

The differentiated nonchondrites in Table 18.1 consist primarily of achondrites which are stony meteorites that lack chondrules and contain evidence of magmatic differentiation, including the segregation of liquid iron and nickel which are insoluble in silicate... 

The first evidence for the conversion of silicate minerals of stony meteorites in Antarctica was reported by Gooding (1986a) who detected the presence of clay mineraloids, gypsum, K-Fe sulfates (jarosite ), and rust on the surfaces and in cracks of achondrites and chondrites from Elephant Moraine (EET) and the Allan Hills. These weathering products had formed primarily from glass and plagioclase in the fusion crust and in cracks in the interiors of the meteorite specimens. 

AEROLITES or STONY METEORITES possess a chemical composition reflecting solar abundances of nonvolatile elements and are subdivided as achondrites and chondrites. ... 

There are four main types of non-chondritic meteorites (Table 10.1). Primitive achondrites, such as the acapulcoites and lodranites, are thought to be from asteroids that experienced only incipient or limited melting (Table 10.1). In contrast, achondrites, iron meteorites, and stony-irons are considered to represent parent bodies that featured widespread melting processes, which ultimately led to planetary differentiation and the formation of a metallic core and a silicate-rich mantle and crust [14, 15]. 

Anhydrous planetesimals, and especially the meteorites derived from them, provide crucial cosmochemical data. Spectroscopic studies of asteroids do not provide chemical analyses, but the spectral similarities of several asteroid classes to known meteorite types provide indirect evidence of their compositions. The few chemical analyses of asteroids by spacecraft are consistent with ordinary chondrite or primitive achondrite compositions. Laboratory analyses of anhydrous meteorites - chondrites, achondrites, irons, and stony irons - allow us to study important chemical fractionations in early solar system bodies. Fractionations among chondrites occur mostly in elements with higher volatility, reflecting the accretion of various components whose compositions were determined by high- and low-temperature processes such as condensation and evaporation. Fractionations among achondrites and irons are more complex and involve partitioning of elements between melts and crystals during differentiation. 

Achondrite A type of stony (low in elemental metals) meteorite. Unlike chrondrites, they do not contain chondrules. 

Differentiated (planetary) Achondrites Angrites Aubrites Brachinites HED meteorites Eucrites Howardites Diogenites Ureilites Stony-irons Pallasites... 

The differentiated meteorites were derived from parent bodies that experienced large-scale partial melting, isotopic homogenization (ureilites are the only exception), and subsequent differentiation. Based on abundance of FeNi-metal, these meteorites are commonly divided into three types achondrites (metal-poor), stony irons, and irons each of the types contains several meteorite groups and ungrouped members. 

Mineralo cal diversity increased with the advent of asteroid melting and differentiation - processes that resulted in the large-scale separation of stony and metallic components. Differentiated meteorites include several classes of stony achondrites, as well as stony-iron and iron meteorites. Nevertheless, no more than -150 mineral species are known to occur in all types of meteorites. These minerals, dominated by magnesium silicates, provided raw materials for the accreting Earth. 

Spectral reflectances of some meteorites match those of some asteroid types irons or E chondrites with M type enstatite achondrites with E type the unique carbonaceous chondrite Tagish Lake with D type HED achondrites with V type stony-irons with most S type thermally metamorphosed carbonaceous chondrites (see below) with C, G, B and F types. (Relative... 

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