(EHa4 in Weyrauch et al., 2018)
Fell April 7, 1891
39° 45′ N., 46° 40′ E. At 8:10 P.M., people in Azerbaydzhan, SSR, USSR, witnessed a A fireball is another term for a very bright meteor, generally brighter than magnitude -4, which is about the same magnitude of the planet Venus as seen in the morning or evening sky. A bolide is a special type of fireball which explodes in a bright terminal flash at its end, often with visible fragmentation. Click on Term to Read More accompanied by detonations. The next morning, a single 27 kg stone was recovered. Indarch has experienced minimal impact alteration, exhibiting weak Metamorphism produced by hypervelocity impact between objects of substantial size moving at cosmic velocity (at least several kilometers per second). Kinetic energy is converted into seismic and heat energy almost instantaneously, yielding pressures and temperatures far in excess those in normal terrestrial metamorphism. On planetary bodies with no atmosphere, smaller Click on Term to Read More (S3) at shock pressures of 5–10 GPa. This produced planar fractures in Group 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 Click on Term to Read More and twinned clinoenstatite, along with metallic shock veins.
|Type of meteorite high in the mineral enstatite and also referred to as E-chondrites. Although they contain substantial amounts of Fe, it is in the form of Ni-Fe metal or sulfide rather than as oxides in silicates. Their highly reduced nature indicates that they formed in an area of the Click on Term to Read More SUBGROUPS
Weyrauch et al., 2018
|Troilite||Cr <2 wt%||Cr >2 wt%||Cr <2 wt%||Cr >2 wt%|
|(Mn,Mg,Fe)S||Fe <20 wt%||Fe >20 wt%||Fe <20 wt%||Fe >20 wt%|
|Kamacite||Ni <6.5 wt%||Ni >6.5 wt%||Ni <6.5 wt%||Ni >6.5 wt%|
A few other E chondrites with intermediate mineralogy have also been identified, including LAP 031220 (EH4), QUE 94204 (EH7), Y-793225 (E-an), LEW 87223 (E-an), and PCA 91020 (possibly related to LEW 87223). Studies have determined that these meteorites were not derived from the EH or EL source through any metamorphic processes, and some or all of them could represent separate E chondrite asteroids. The revised E chondrite classification scheme of Weyrauch et al. (2018) including selected examples from their 80-sample study can be found here. It was determined that Indarch is a member of the EHa subgroup.Indarch contains both silicate-rich and metal-rich Roughly 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 Click on Term to Read More embedded within a sulfide-rich Fine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents. Click on Term to Read More. A two-stage cooling history has been suggested to explain the reversed zoning in the chondrules. Other minerals present in Indarch include sub-µm-sized, presolar SiC grains in a concentration of 1.3 Parts per million (106). (Huss, 1990). These have a grain size closely matching that of unprocessed circumstellar grains, and S-isotopic compositions consistent with an origin on Stars on the Asymptotic Giant Branch, which represents a late stage of stellar evolution that all stars with initial masses < 8 Msun go through. At this late stage of stellar evolution, gas and dust are lifted off the stellar surface by massive winds that transfer material to the interstellar Click on Term to Read More (Gyngard et al., 2012). The silicon-containing nitride, nierite, also occurs, which some investigators concluded was formed by Segregation, during cooling, of a homogeneous solid solution into two or more different solids. Click on Term to Read More of kamacite, perryite, and Ni-Fe phosphide mineral, (Fe,Ni)3P, yellowish in color and predominantly found in iron and stony-iron meteorites. Schreibersite can also be found in a variety of other meteorites including some acapulcoites, aubrites, enstatite chondrites and achondrites, lunars, ureilites, winonaites and a smattering of other meteorite types like CM, CO and CB. Schreibersite Click on Term to Read More during The body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. Click on Term to Read More metamorphism (Alexander et al., 1994). However, an advanced isotopic study conducted by Leitner et al. (2018) led to their contention that the majority of the silicon nitride was formed by nebular condensation/precipitation processes (a rare component is presolar) prior to its incorporation into the EC parent body. Micro- and nano-scale diamonds are present in Indarch at a concentration of ~17 ppm, and the sulfide minerals Mn-Ca sulfide, (Mn,Ca)S, is a pale to dark brown accessory mineral found in minor amounts in highly reduced meteorites such as many enstatite chondrites, and some aubrites and enstatite achondrites. Oldhamite in enstatite chondrites likely formed by solar nebular gas condensation. CaS Oldhamite was also found in the most fresh Click on Term to Read More and niningerite have also been identified. By using 53Mn/53Cr ratios as a chronometer for absolute ages, Shukolyukov and Lugmair (2004) estimated the age of Indarch to be 4.565 b.y. A similar age of ~4.563 b.y. was determined by Busfield et al. (2008) based on I–Xe systematics, while Moseley et al. (2011) calculated an age based on Mn–Cr systematics and anchored to D’Orbigny of ~4.5674 b.y. These ages are similar to that of EH4 Abee, but slightly older than EL6 Khairpur, possibly reflecting Khairpur’s extended cooling history. The K–Ar closure age as determined by Bogard et al. (2010) occurred ≥4.35 b.y., and evidence indicates a later impact-degassing event 4.25 b.y. ago. A Rb–Sr isochron gives an age of 4.52 (±0.15) b.y., while a corrected Rb–Sr age gives 4.50 b.y. Indarch has a matrix CRE age based on 3He, 21Ne, and 38Ar of 12.1 (±2.5) m.y. (Eugster et al., 2007). Although E chondrites and Aubrites are named for the Aubres meteorite that fell in 1836 near Nyons, France. They are an evolved achondrite that is Ca-poor and composed mainly of enstatite (En100) and diopside (En50Wo50) with minor amounts of olivine (Fa0) and traces of plagioclase (An2-8). They contain large white crystals of enstatite as Click on Term to Read More share a common O-isotopic signature, some chemical and mineralogical differences exist which had previously cast doubt on their formation on a common parent body. Some of these differences include the higher abundance of Ti and Pure* magnesium end-member (Mg2SiO4) of the olivine solid solution series and an important mineral in meteorites. When magnesium (Mg) is completely substituted by iron, it yields the the pure Fe-olivine end member, fayalite (Fe2SiO4). The various Fe and Mg substitutions between these two end-members are described based on their forsteritic (Fo) Click on Term to Read More in aubritic sulfides than in E chondrites. A scenario reconciling these differences has been presented in light of an experiment in which an E chondrite was systematically melted in a highly Oxidation 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 Click on Term to Read More, oxygen-depleted environment. In the experiment, as the silicate-melt reached a temperature range of 1000–1300°C having a degree of An igneous process whereby rocks melt and the resulting magma is comprised of the remaining partially melted rock (sometimes called restite) and a liquid whose composition differs from the original rock. Partial melting occurs because nearly all rocks are made up of different minerals, each of which has a different melting Click on Term to Read More of 20%, the metal–sulfide component began to migrate out of the The 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. At 1450°C, a completely separated Element 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 Click on Term to Read More component could have begun to establish a metallic In the context of planetary formation, the core is the central region of a large differentiated asteroid, planet or moon and made up of denser materials than the surrounding mantle and crust. For example, the cores of the Earth, the terrestrial planets and differentiated asteroids are rich in metallic iron-nickel. Click on Term to Read More on its parent body. Since the sulfides melted at temperatures as low as 1000°C, it is demonstrated that aubritic sulfides cannot be a product of nebular synthesis as previously speculated. Instead, the tranfer of S and Ca from the S-rich silicate melts resulted in magmatic Physical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. Click on Term to Read More of oldhamite (CaS). Additionally, a phase was reached at 1500°C in which tectosilicate was Oxidation 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 Click on Term to Read More to Si within the metallic melt, with the subsequent crystallization of forsterite. Moreover, Ti-rich troilite crystallized from a combination of an Fe-rich sulfide melt, and a mixed-sulfide melt. All of the results of the experiment are consistent with a derivation of the aubrites from an E chondrite-type precursor in a strongly reducing, oxygen-depleted environment. Previous studies employing multiple lines of evidence including chemical, petrographic, metamorphic, and cosmic-ray Time interval that a meteoroid was an independent body in space. In other words, the time between when a meteoroid was broken off its parent body and its arrival on Earth as a meteorite - also known simply as the "exposure age." It can be estimated from the observed effects Click on Term to Read More data, suggest that the EL and EH chondrites originated in different layers of the same asteroidal parent body. More recently, very precise isotopic measurements were made of a statistically larger sampling of E chondrites and aubrites. Although their O-isotopic data were indeed identical, a three-isotope plot distinguished the EH group from the EL and Aubrites are named for the Aubres meteorite that fell in 1836 near Nyons, France. They are an evolved achondrite that is Ca-poor and composed mainly of enstatite (En100) and diopside (En50Wo50) with minor amounts of olivine (Fa0) and traces of plagioclase (An2-8). They contain large white crystals of enstatite as Click on Term to Read More groups by its slightly steeper slope; the plots of the EL and aubrite groups were co-linear with the terrestrial Concentration or separation of one mineral, element, or isotope from an initially homogeneous system. Fractionation can occur as a mass-dependent or mass-independent process. Click on Term to Read More line. A third grouplet with intermediate mineralogy has recently been identified, represented by the Work in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More Y-793225. Studies have determined that it was not derived from material associated with the EH or the EL groups through any metamorphic processes, and therefore could represent a unique enstatite parent body. The Shallowater meteorite is also widely considered to originate from a unique enstatite parent object. The iron-rich, oxygen-poor composition of Indarch, as well as its greater depletion of refractories than is found on the Earth, has led to speculation that E chondrites might have once been a part of the pre-differentiated outer layer of Mercury. However, reflectance spectrometry has determined that E-type and M-type asteroids are similar to E chondrites, and that they occupy stable orbits between 1.8 and 3.2 The astronomical unit for length is described as the "mean" distance (average of aphelion and perihelion distances) between the Earth and the Sun. Though most references state the value for 1 AU to be approximately 150 million kilometers, the currently accepted precise value for the AU is 149,597,870.66 km. The Click on Term to Read More. These findings suggest that the Belt located between 2.12 and 3.3 AU from the Sun and located between the orbits of Mars and Jupiter containing the vast majority of asteroids. The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such Click on Term to Read More is where they originated, or more likely, to where they were collisionally and/or gravitationally relocated. A Centered around a sun. Our own Solar System is centered around the Sun so that all planets such as Earth orbit around the Sun. Note that 25% of Americans incorrectly believe the Sun revolves around the Earth. Click on Term to Read More distance of ~2.0–2.9 AU was calculated for two E chondrites on the basis of their implanted solar Element occurring in the right-most column of the periodic table; also called "inert" gases. In these gases, the outer electron shell is completely filled, making them very unreactive. Click on Term to Read More concentrations (Nakashima et al., 2004). By utilizing Mn–Cr isotopic systematics, Shukolyukov and Lugmair (2004) concluded that the E chondrites formed at a location closer to the Sun—between at least 1 AU outward to 1.4 AU—than that which they now occupy. Furthermore, an anomalous light N component found proportionately in carbonaceous and E chondrites but not on Earth, and which is almost certainly of nucleosynthetic origin, attests to a similar heliocentric location for the formation of these bodies. Details of a computer-based model (Blander et al., 2009) of the formation history of E chondrites can be found on the Sahara 97096 page. The specimen of Indarch shown above is a 1.0 g cut fragment.