DiogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
(>40 vol% 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 Click on Term to Read More)
click on photo for a magnified view Purchased 2002
no coordinates recorded A single 49 g stone with weathered fusion crustMelted exterior of a meteorite that forms when it passes through Earth’s atmosphere. Friction with the air will raise a meteorite’s surface temperature upwards of 4800 K (8180 °F) and will melt (ablate) the surface minerals and flow backwards over the surface as shown in the Lafayette meteorite photograph below. Click on Term to Read More was found near Lake Iriqui, Morocco, and was subsequently purchased through a Moroccan dealer in March 2002 by A. and G. Hupé. Analysis 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 Click on Term to Read More was conducted at the University of Washington in Seattle (A. Irving and S. Kuehner). 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 Click on Term to Read More isotopeOne of two or more atoms with the same atomic number (Z), but different mass (A). For example, hydrogen has three isotopes: 1H, 2H (deuterium), and 3H (tritium). Different isotopes of a given element have different numbers of neutrons in the nucleus. Click on Term to Read More data indicate that NWA 1459 originated on the HED 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. Click on Term to Read More, and it was classified as a rare olivine-rich diogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More.
This meteorite has a coarse-grained texture and a dark yellow-green color, and it exhibits minor staining caused by terrestrial weathering products such as iron oxides/hydroxides. It contains an unusual abundance of chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More
grains, the presence of which is associated with high temperatures. Some of the chromite grains protrude across the crusted surface, selectively exposed and polished by atmospheric ablationGradual removal of the successive surface layers of a material through various processes. • The gradual removal and loss of meteoritic material by heating and vaporization as the meteoroid experiences frictional melting during its passage through the atmosphere. The resulting plasma ablates the meteor and, in cases where a meteor Click on Term to Read More
processes. Minor constituents that are present include anorthitic plagioclaseAlso referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite Click on Term to Read More
, clinopyroxene, troiliteBrass colored non-magnetic Fe sulfide, FeS, found in a variety of meteorites.
, and Ni-free (0.06%) Fe-metal.
At the time of its classification, the olivine diogenitesDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
included only a few like members, some of which had previously been found in Antarctica. The olivine-rich GRA 98108 has an orthopyroxeneOrthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur Click on Term to Read More
content of 70% (Mg# = 69–79) and an olivine content of 30% (Mg# = 73), along with minor plagioclase, chromite, FeNi-metal, and troilite (Righter, 2001). Another unusually olivine-rich diogenite is the unbrecciated ALHA77256. In addition, the genomict brecciaWork in Progress ... A rock that is a mechanical mixture of different minerals and/or rock fragments (clasts). A breccia may also be distinguished by the origin of its clasts: (monomict breccia: monogenetic or monolithologic, and polymict breccia: polygenetic or polylithologic). The proportions of these fragments within the unbrecciated material Click on Term to Read More
EETA79002 contains a large amount of olivine (Mg# = ~76) in at least one lithology, mainly associated with highly magnesian orthopyroxene grains (Mittlefehldt, 2000). As with the other olivine diogenite samples, this highly magnesian orthopyroxene lithology is thought to have originated from a harzburgitic (olivine + orthopyroxene) plutonGeology: Igneous intrusive body that forms when magma is injected into host rocks and solidifies. Plutons occur in the crust of asteroids undergoing differentiation or planets. Named after Pluto, the Roman god of the underworld. Plutonic rocks are the rocks found within a pluton. Astronomy: Category of planet including all Click on Term to Read More
. However, olivine in this diogenite is not in equilibriumTerm used to describe physical or chemical stasis. Physical equilibrium may be divided into two types: static and dynamic. Static equilibrium occurs when the components of forces and torques acting in one direction are balanced by components of forces and torques acting in the opposite direction. A system in static Click on Term to Read More
with some other orthopyroxene lithologies that are present, suggesting that this is a genomict breccia consisting of a mixture of harzburgite and more common Fe-rich orthopyroxene (orthopyroxeniteA rock composed primarily of orthopyroxene. Non-terrestrial orthopyoxenites include diogenites and a single martian meteorite, ALH 84001, that was found in the Allan Hills region of Antarctica in 1984. ALH 84001 is a cumulate rock consisting of 97% coarse-grained, Mg-rich orthopyroxene, with small amounts of plagioclase, chromite, and carbonate. It Click on Term to Read More
) clasts (Beck and McSween Jr., 2009).
Northwest Africa 1459 is classified as a harzburgitic peridotite rock, with a higher olivine (~40 vol%) and Fe content than that found in all previously analyzed olivine-rich diogenites. In 2003, a fifth member of this olivine-rich diogenite group was found, NWA 1877 and pairings, which contains ~45 vol% olivine with no plagioclase suggesting that it formed at a greater depth than did NWA 1459. This meteorite, along with NWA 1459, GRA 98108, ALHA 77256, and EETA 79002, provided the requisite number required to form a new group that was proposed to be called the olivine diogenite group—a term generally associated with those diogenites containing at least 5 vol% olivine (A. Irving et al.
, 2005). For those diogenites with between 1 vol% and 5 vol% olivine the term ‘olivine-bearing’ is most commonly used. Even more recently, the classification of several new olivine diogenites was published; namely, NWA 5405 (~10 vol% olivine), NWA 5312 (24 vol% olivine), MIL 07001 (>40 vol% olivine), NWA 4223 (50 vol% olivine), and NWA 5480 (57 vol% olivine). While it is hypothesized that olivine diogenites are cumulates constituting distinct layered magmatic intrusions emplaced into the crustOutermost layer of a differentiated planet, asteroid or moon, usually consisting of silicate rock and extending no more than 10s of km from the surface. The term is also applied to icy bodies, in which case it is composed of ices, frozen gases, and accumulated meteoritic material. On Earth, the Click on Term to Read More
, the unusual features exhibited in NWA 5480 suggest a possible origin as a mantleMain silicate-rich zone within a planet between the crust and metallic core. The mantle accounts for 82% of Earth's volume and is composed of silicate minerals rich in Mg. The temperature of the mantle can be as high as 3,700 °C. Heat generated in the core causes convection currents in Click on Term to Read More
residue. A relatively strong paleomagnetic intensity of ~36 µT was measured for NWA 5480 (Tarduno and Cottrell, 2012), from which a dynamo can be inferred to have existed during crystallizationPhysical 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
more than 19.68 m.y. after 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 Click on Term to Read More
(Yin et al.
, 2018). Analyses by Yamaguchi et al.
(2013) led them to conclude that the NWA 5480 diogenite is an impact melt rockRock that has been made temporarily molten as a result of the energy released by the impact of a large colliding body. Impact melts include small particles, known as "impact melt spherules" that are splashed out of the impact crater, and larger pools and sheets of melt that collect in Click on Term to Read More
formed at the bottom of a large basin such as Rheasilvia.
It is noteworthy that O-isotope and trace elementSubstance composed of atoms, each of which has the same atomic number (Z) and chemical properties. The chemical properties of an element are determined by the arrangement of the electrons in the various shells (specified by their quantum number) that surround the nucleus. In a neutral atom, the number of Click on Term to Read More
data for the unique 1.1 g olivine-rich (dunitic/harzburgitic?) achondriteAn achondrite is a type of stony meteorite whose precursor was of chondritic origin and experienced metamorphic and igneous processes. They have a planetary or differentiated asteroidal origin where the chondritic parent body reached a sufficient size that through heating due to radioactive decay of 26Al (aluminum isotope) and gravitational Click on Term to Read More
QUE 93148 have led to the suggestion that it might be derived from the deep mantle of the HED parent body (Goodrich and Righter, 2000; C. Floss, 2003). However, due to its lower Co and Ni abundances than what would otherwise be expected for an olivine-rich mantle lithology or magma oceanCompletely molten surfaces of terrestrial planets or moons that formed soon after accretion. Samples returned by the Apollo missions provide evidence of a lunar magma ocean, crystallization of which produced a stratified Moon with a low-density crust formed by accumulation of the mineral plagioclase overlying a higher density mantle of Click on Term to Read More cumulateIgneous rock composed of crystals that have grown and accumulated (often by gravitational settling) in a cooling magma chamber. Click on Term to Read More
, QUE 93148 may have actually originated on a distinct planetary body such as that of the main-group pallasites (Shearer et al.
, 2008; Shearer et al.
Northwest Africa 1459 may be different from the other olivine-rich diogenites in being a recrystallized cumulate (Irving et al.
, 2003). Some have suggested a formation of olivine diogenites from basaltBasalt is the most common extrusive igneous rock on the terrestrial planets. For example, more than 90% of all volcanic rock on Earth is basalt. The term basalt is applied to most low viscosity dark silicate lavas, regardless of composition. Basalt is a mafic, extrusive and fine grained igneous rock Click on Term to Read More
depleted source regions—melts from which eucritesMost common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after Click on Term to Read More
had previously been derived. However, due to the minor and trace element overlaps observed among the diogenite types, they may in fact form a continuum of orthopyroxene accumulation within a fractionated magmaMolten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. Click on Term to Read More
ocean or layered intrusion emplaced into the crust. Alternatively, they may represent distinct parental magma sources rather than originating in a separate mantle setting (Shearer et al.
, 2007, 2010; Barrat and Yamaguchi, 2014). It was argued that only the largest impact event could excavate olivine-rich mantle material on VestaThird largest and fourth brightest asteroid; it was discovered in 1807 by Heinrich Olbers and named for the ancient Roman goddess of the hearth. 4 Vesta has a basaltic surface composition and an average density not much less than that of Mars. Evidently lava once flowed here indicating that the
, and this is exemplified by the central uplift within the Southern Lowlands craterBowl-like depression ("crater" means "cup" in Latin) on the surface of a planet, moon, or asteroid. Craters range in size from a few centimeters to over 1,000 km across, and are mostly caused by impact or by volcanic activity, though some are due to cryovolcanism. Click on Term to Read More
where even coreIn 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
material may have been exposed (Delaney, 2009). This tremendous impact event is estimated to have displaced 10–20% of the mass of the asteroid. Notably, Beck et al.
(2012) identified the first olivine-rich melt material in the howardites that constitute the PCA 02009 pairing group. This olivine-rich material was likely derived from harzburgitic and dunitic lithologies exposed on the surface of Vesta.
Importantly, the dunitic Vesta-related meteorite NWA 2968
(>95 vol% olivine) may be the deepest sampled lithology known from the HED parent asteroid, widely thought to be 4 Vesta and its derivitive Vestoids. In a similar manner, it is envisaged by one investigative team that Vesta and the Vestoids, along with the isotopically similar mesosiderites and IIAB irons, were themselves the products of a breakup of an even larger parent object which they have named ‘Opis’ (Irving et al.
, 2009). In Greek mythology, Opis was the wife of Saturn, whose children were Jupiter, Neptune, Pluto, Juno, Ceres, and Vesta.
To see an alternative classification 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
for the diogenites based on mineralogical and petrographical features, proposed by Beck and McSween (2010) and modified by Wittke et al.
(2011), click here
. The photo above shows the cut side of a 0.42 g partial end section of NWA 1459. The photo of the main massLargest fragment of a meteorite, typically at the time of recovery. Meteorites are commonly cut, sliced or sometimes broken thus reducing the size of the main mass and the resulting largest specimen is called the "largest known mass". Click on Term to Read More
shown below is courtesy of A. and G. Hupé.
NORTHWEST AFRICA 1459
Photo courtesy of A. and G. Hupé