EucriteMost 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
Monomict, recrystallized noncumulate
(Main Group–Nuevo Laredo trend)
Found Winter 1996/97
27° 10′ N., 16° 08′ E.
An unusual 1,425 g oriented basaltic 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 found in the Libyan Sahara Desert and classified after extensive work as a new type of eucriteMost 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
by Hiroshi Takeda et al.
. It was submitted to the Nomenclature Committee and designated Dar al Gani 647.
The 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 Click on Term to Read More
and 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
in the matrixFine 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
are recrystallized to a fine-grained granoblastic crystalline texture, which masks the original fragmental texture commonly observed in other monomict 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
. Dusty pyroxene crystals caused by the presence of chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More
and ilmeniteTi-Fe oxide, TiFeO3, found in achondrites, lunar mare basalts, and shergottites. Ilmenite forms as a primary mineral in mafic igneous rocks. It crystallizes relatively early out of a magma before most of the other minerals, and as a result, the heavier crystals of ilmenite precipitate to the bottom of the magma Click on Term to Read More
are similar to those found in other monomict eucrites and were probably present before the recrystallization phase. A rare silicaSilicon dioxide, SiO2. 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 Click on Term to Read More
has also been identified.
In light of its unique mineralogy and textures, DaG 647 appears to have experienced a two-stage thermal history followed by rapid cooling. The initial brecciationThe formation of a breccia through a process by which rock fragments of of various types are recemented or fused together. Click on Term to Read More
and metamorphism occurred early in the crustal evolution of the eucrite 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
, probably 4 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
. During this initial metamorphism, the dusty pyroxenes that are characteristic of monomict eucrites were produced. Based on the homogeneous composition of the plagioclase crystals, usually identified only with 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
eucrites, it can be inferred that DaG 647 later experienced recrystallization at high temperatures (~980°C) followed by an extensive and prolonged annealing phase which homogenized the plagioclase. It was then rapidly cooled (by excavation?) without further shock.
Dar al Gani 647 has a CRE age of ~25 m.y., similar to that of DaG 480, but also an age that references a cluster of HED meteorites that reflects a possible major impact on their parent body. Dar al Gani 647 might be paired with DaG 567. The specimen of DaG 647 pictured above is a 0.6 g very thin partial slice with some remnant 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