DaG 734

EL4
(ELa4 in Weyrauch et al., 2018)

Found Winter 1996/97
27° 7.91′ N., 16° 3′ E. Several stones weighing a total of 1,378 g were found in the Libyan Sahara. Studies performed at the Max–Planck–Institut für Chemie in Mainz, Germany by Frank Wlotzka have led to the classification of this meteoriteWork 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 as an EL4 chondriteChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such. The 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 texture and average size of 0.45 (±0.2) mm, and the size of the matrixFine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents. 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). crystals, indicate that this is an EL4 meteorite. Among EL chondritesChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such, the 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. 4 sample is the most poorly represented in our collections, with the 1.2 g QUE 94368 being the first such meteorite found (although initially classified as an E5, QUE 94368 was subsequently determined to be an EL4; A. Rubin, 1997). Dar al Gani 734 is a highly weathered (W4) and friable meteorite.

Enstatite chondrites were formed in a highly reducingOxidation 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 environment. Therefore, they contain virtually no 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 in the oxide form—an amount much less than other chondrites, and even the terrestrial planetsRocky planets: Mercury, Venus, Earth, and Mars. These planets have physical characteristics, chemical composition and internal structure similar to the Earth. The terrestrial planets have 0.4% of the total mass of all the planets in the Solar System. Some large satellites of planets are also similar to the characteristics of. The mineralInorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous sinoite (silicon oxynitride) has been found to occur in many EL chondrites that have high bulk N contents, and is associated with crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. from an impact melt. This suggests that there was a period of high-temperature, melt-forming conditions followed by annealing, and subsequently, a late shock to stage S2.

Previously, employing multiple lines of evidence including chemical, petrographic, metamorphicRocks that have recrystallized in a solid state due to changes in temperature, pressure, and chemical environment., and cosmic-ray exposure ageTime 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 data, studies suggested that the EL and EH chondrites originate from different layers on the same parent bodyThe 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.. More recently, very precise isotopic measurements were made of a statistically larger sampling of E chondrites and aubritesAubrites 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. Although their O-isotopic data were indeed identical, a three-isotope plot distinguished the EH group from the EL and aubriteAubrites 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 groups by its slightly steeper slope; the plots of the EL and aubrite groups were collinear with the terrestrial fractionationConcentration or separation of one mineral, element, or isotope from an initially homogeneous system. Fractionation can occur as a mass-dependent or mass-independent process. line. A third grouplet with intermediate mineralogy has recently been identified, represented by the meteorite Y-793225. Studies have determined that it was not derived from the EH or EL groups through any metamorphic processes, and thus might represent a unique enstatite parent body. Likewise, the Shallowater meteorite is thought to have originated on a unique enstatite parent body.

Weyrauch et al. (2018) analyzed the mineral and chemical data from 80 enstatite chondrites representing both EH and EL groups and spanning the full range of petrologic types for each group. They found that a bimodality exists in each of these groups with respect to both the Cr content in troiliteBrass colored non-magnetic mineral of iron sulfide, FeS, found in a variety of meteorites. and the Fe concentration in niningerite and alabanditeMagnesium sulfide found in aubrites and EL chondrites. Its formula is MnS. (endmembers of the [Mn,Mg,Fe] solid solutionCompositional variation resulting from the substitution of one ion or ionic compound for another ion or ionic compound in an isostructural material. This results in a mineral structure with specific atomic sites occupied by two or more ions or ionic groups in variable proportions. Solid solutions can be complete (with series present in EH and EL groups, respectively). In addition, both the presence or absence of daubréelite and the content of Ni in kamaciteMore common than taenite, both taenite and kamacite are Ni-Fe alloys found in iron meteorites. Kamacite, α-(Fe,Ni), contains 4-7.5 wt% Ni, and forms large body-centered cubic crystals that appear like broad bands or beam-like structures on the etched surface of a meteorite; its name is derived from the Greek word were demonstrated to be consistent factors for the resolution of four distinct E chondrite groups: EHa, EHb, ELa, and ELb (see table below).

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 DaG 734 is a member of the ELa subgroup.

OxygenElement that makes up 20.95 vol. % of the Earth's atmosphere at ground level, 89 wt. % of seawater and 46.6 wt. % (94 vol. %) of Earth's crust. It appears to be the third most abundant element in the universe (after H and He), but has an abundance only isotopic studies place the formation of enstatite chondrites on the terrestrial fractionation line, which is taken by some to mean that they formed within the inner Solar SystemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids.. Based on Mn–Cr isotopeOne of two or more atoms with the same atomic number (Z), but different mass (A). For example, hydrogen has three isotopes: H, H (deuterium), and H (tritium). Different isotopes of a given element have different numbers of neutrons in the nucleus. systematics and its correlation with heliocentricCentered 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. distance, Shukolyukov and Lugmair (2004) concluded that E chondrites originated ~1.0–1.4 AUThe 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 from the SunOur parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the before being perturbed into their present locations in the asteroid beltBelt 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. Similarly, Nakashima et al. (2006) calculated a heliocentric distance of >1.1 and 1.3 AU for two EL3 chondrites (ALH 85119 and MAC 88136, respectively) on the basis of their implanted solar noble gasElement 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. concentrations. In contrast, the identification of the E-asteroid group, including Hungaria at 1.94 AU, Nysa at 2.42 AU, and Angelina at 2.68 AU, suggests that the actual solar region of formation may lie at a greater heliocentric distance. Cosmochemists are presently trying to construct a suitable theory involving oxygen depletion in this E-asteroid region of the 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 with to explain the conflicting data.

The specimen of DaG 734 pictured above is a 5.2 g slice displaying an advanced stage of weathering due to its extended terrestrial residence, consistent with the extreme rarity of this meteorite. An abundance of large 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 is a characteristic that distinguishes DaG 734 from the smaller-sized chondrules found in the EH group. The complete lack of visible free metal in this meteorite is likely a reflection of its advanced stage of weathering.