Define "Chondrite" : SkyFall Meteorites Glossary

Chondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicateThe most abundant group of minerals in Earth's crust, the structure of silicates are dominated by the silica tetrahedron, SiO44-, with metal ions occurring between tetrahedra). The mesodesmic bonds of the silicon tetrahedron allow extensive polymerization and silicates are classified according to the amount of linking that occurs between the minerals (found in both chondrulesRoughly spherical aggregate of coarse crystals formed from the rapid cooling and solidification of a melt at ~1400 ° C. Large numbers of chondrules are found in all chondrites except for the CI group of carbonaceous chondrites. Chondrules are typically 0.5-2 mm in diameter and are usually composed of olivine and fine grained matrixFine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents.), reducedOxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons, while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants Fe/Ni metalElement that readily forms cations and has metallic bonds; sometimes said to be similar to a cation in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. A diagonal line drawn (found in various states like large blebs, small grains and/or even chondruleRoughly spherical aggregate of coarse crystals formed from the rapid cooling and solidification of a melt at ~1400 ° C. Large numbers of chondrules are found in all chondrites except for the CI group of carbonaceous chondrites. Chondrules are typically 0.5-2 mm in diameter and are usually composed of olivine rims), and various refractory inclusionsInclusions found predominantly in carbonaceous chondrites and are rich in refractory elements particularly calcium, aluminum and titanium that in various combinations form minerals such as spinel, melilite, perovskite and hibonite. There are two types of refractory inclusion: • Ca Al-rich inclusions (CAIs) • Amoeboid olivine aggregates (AOAs) Refractory inclusions were (such as Ca-Al-rich InclusionsSub-millimeter to centimeter-sized amorphous objects found typically in carbonaceous chondrites and ranging in color from white to greyish white and even light pink. CAIs have occasionally been found in ordinary chondrites, such as the L3.00 chondrite, NWA 8276 (Sara Russell, 2016). CAIs are also known as refractory inclusions since they (CAIsSub-millimeter to centimeter-sized amorphous objects found typically in carbonaceous chondrites and ranging in color from white to greyish white and even light pink. CAIs have occasionally been found in ordinary chondrites, such as the L3.00 chondrite, NWA 8276 (Sara Russell, 2016). CAIs are also known as refractory inclusions since they) found in many carbonaceous chondrites and a few rare ordinary chondrites). These components have remained largely unchanged since their formation within the accretion diskDisk-shaped cloud of gas and solids in orbital motion around a central protostar or some other massive central body. ~4.5 Ga at the beginning of our Solar SystemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids.. CAIs and chondrules studied today experienced a complicated series of high-temperature events as isolated grains in the disk before developing into planetesimalsHypothetical solid celestial body that accumulated during the last stages of accretion. These bodies, from ~1-100 km in size, formed in the early solar system by accretion of dust (rock) and ice (if present) in the central plane of the solar nebula. Most planetesimals accreted to planets, but many – that went on to experience additional thermal and aqueous alteration. They therefore provide important evidence of the constraints at multiple points in time and location on the evolving dynamics, physical and chemical processes during the formation of the accretionAccumulation of smaller objects into progressively larger bodies in the solar nebula leading to the eventual formation of asteroids, planetesimals and planets. The earliest accretion of the smallest particles was due to Van der Waals and electromagnetic forces. Further accretion continued by relatively low-velocity collisions of smaller bodies in the disk and early solar systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with¹. ... Expand

Except for the lightest elements (e.g., H, He), chondrites have the same elemental composition as the original solar nebulaThe primitive gas and dust cloud around the Sun from which planetary materials formed. because they come from planetesimals that never melted or underwent differentiationA process by which a generally homogeneous chondritic body containing mostly metal, silicates and sulfides will melt and form distinct (differentiated) layers of different densities. When the melting process continues for a long enough period of time, the once chondritic body will re-partition into layers of different composition including. Chondrites are so named because they nearly all contain chondrules – small round droplets of olivineGroup of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion and pyroxeneA class of silicate (SiO3) minerals that form a solid solution between iron and magnesium and can contain up to 50% calcium. Pyroxenes are important rock forming minerals and critical to understanding igneous processes. For more detailed information, please read the Pyroxene Group article found in the Meteoritics & Classification category.. Chondrules are one of the first solids to have condensed and crystallized in the solar nebulaAn immense interstellar, diffuse cloud of gas and dust from which a central star and surrounding planets and planetesimals condense and accrete. The properties of nebulae vary enormously and depend on their composition as well as the environment in which they are situated. Emission nebula are powered by young, massive and all similar in bulk composition to the Sun’s photospherePoint where a star's atmosphere appears to become completely opaque. Thus, the photosphere may be thought of as the imaginary surface from which the starlight that we see appears to be emitted. The photosphere is not a thin surface; the Sun's photosphere has a thickness of ~100 km. (Within that. Variations in chemical composition among chondrites reflect formation of their parent bodies in different regions of the solar nebula. The main groups are carbonaceous chondrites (CC), enstatiteA mineral that is composed of Mg-rich pyroxene, MgSiO3. It is the magnesium endmember of the pyroxene silicate mineral series - enstatite (MgSiO3) to ferrosilite (FeSiO3). chondrites (E), ordinary chondrites (OC) including the H, L, and LL groups, and rumurutiites (R). Other, rarer chondrite groups are F-chondrites, G-chondrites and kakangariites (K).

Each group is further subdivided into petrologic types 1 through 7. Types 1 and 2 show evidence of aqueous alteration to the extent that chondrules are either absent (Type 1) or rare (Type 2). Petrologic types 3 to 7 show evidence of varying degrees of thermal metamorphism, which is reflected by modification of the chondrules and chemical homogenization. Type 3 chondrites display unaltered and distinct chondrules, whereas the chondrules become increasingly indistinct due to recrystallization/equilibration in types 4 to 6. Type 7 chondrites, better termed metachondrites, in which chondrules are absent, are transitional between chondrites and primitive achondrites.

Aqueous alteration and thermal metamorphism used to be considered as separate processes leading to the linear petrologic typeMeasure of the degree of aqueous alteration (Types 1 and 2) and thermal metamorphism (Types 3-6) experienced by a chondritic meteorite. Type 3 chondrites are further subdivided into 3.0 through 3.9 subtypes. scale from Type 1 to Type 7. However, it is now clear that fluids of some kind were present during thermal processing of virtually all chondrite classes, and thermal alteration played a role in virtually all chondrite classes including many carbonaceous chondriteCarbonaceous chondrites represent the most primitive rock samples of our solar system. This rare (less than 5% of all meteorite falls) class of meteorites are a time capsule from the earliest days in the formation of our solar system. They are divided into the following compositional groups that, other than types.

Chondrite

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