L impact-melt rock
(H/L6 impact-melt clastA mineral or rock fragment embedded in another rock. Click on Term to Read More in MetBull 90)
(H/L6-melt rock in MetBull Database)
Purchased before 2006
no coordinates recorded Two pieces of a single stone weighing together 436.4 g were found in Northwest Africa and sold in Erfoud, Morocco to 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 collector C. Anger of Austromet. A sample was submitted for analysis and classification to the Museum für Naturkunde (A. Greshake and M. Kurz), and it was initially determined that NWA 4150 is a unique melt lithology belonging to the transitional H/L-chondrite group. This initial classification has been revised based on continued study (Wittmann et al., 2011).
Northwest Africa 4150 has an average 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
Fa value of 24.1 and an average 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
Fs value of 19.9, values which are in the range of the L-chondrite group. The 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 Click on Term to Read More
abundance of 5% matches that of L 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 Click on Term to Read More
, and the concentration of Co 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 Click on Term to Read More
matches that group as well. A wide variety of 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 Click on Term to Read More
are represented over a much 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 Click on Term to Read More
surface area due to the chondritic melt, and they have average dimensions indistinguishable from those of L chondrites. Along with a quenched melt mesostasisLast material to crystallize/solidify from a melt. Mesostasis can be found in both chondrules, in the matrix around chondrules, and in achondrites as interstitial fine-grained material such as plagioclase, and/or as glass between crystalline minerals. Click on Term to Read More
, the chondrules and microcrystalline 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 Click on Term to Read More
fragments exhibit an excellent state of preservation, and surviving lithic clasts indicate a 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.
of L3–L4 (Wittmann et al.
, 2011). An Fe–S–Si melt covers a significant area, with a cooling rate estimated to be 0.05°C per year, similar to that of L5 Cat Mountain, and corresponding to the metallographic cooling rate at a depth of 1 km. Shock features are prevalent in chondrule fragments, including undulous extinctionIn astronomy, the dimming of starlight as it passes through the interstellar medium. Dust scatters some of the light, causing the total intensity of the light to diminish. It is important to take this effect into account when measuring the apparent brightness of stars. The dark bands running across portions Click on Term to Read More
, planar fractures, mosaicism, and brown olivine. The crystallized impact-melt component contains rounded metal and sulfide particles and aggregates very similar in shape to those in L6 Wickenburg. It is suggested that NWA 4150 formed within a thick 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
lens of a 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
measuring 5–7 km in diameter.
It might be a reasonable assumption that the L impact-melt rock NWA 4150 could be paired with the five member pairing group comprising NWA 4152–4156 which were initially classified as H/L6 chondrites, especially considering that all were found at virtually the same location in the same timeframe, purchased by the same collector, submitted to the same classification lab, and assigned virtually consecutive NWA-series numbers. Moreover, similar scenarios have occurred before, in which a very small percentage of shock-melted stones were discovered associated with a majority of non-melted stones of a common fallMeteorite seen to fall. Such meteorites are usually collected soon after falling and are not affected by terrestrial weathering (Weathering = 0). Beginning in 2014 (date needs confirmation), the NomComm adopted the use of the terms "probable fall" and "confirmed fall" to provide better insight into the meteorite's history. If Click on Term to Read More
, Gao-Guenie. Nevertheless, there are some petrographic features of NWA 4150 that might be inconsistent with such a pairing: its weathering grade of W0/1 is significantly lower than that of the NWA pairing group (W2–4), and its impact melt features reflect a much greater shock event than that commensurate with the NWA pairing group (S3–4). Further analysis is required to make a conclusion on their pairing status.
Another important factor relevant to the pairing question is the olivine Fa content that characterizes NWA 4150 (Fa24.1
) compared to that of the NWA pairing group (Fa19.9
). A recent study by Rubin et al.
(2008), addresses the question of how the oxidationOxidation 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
state of ordinary chondrites (represented by the mean olivine Fa value) varies over different size scales, and this may shed further light on the question of pairing. They found that the Fa values for the chondrites studied were heterogeneous on km-sized scales and above, but homogenous on meter-sized scales and below. It could be inferred that the Fa values of all stones that are derived from a single multi-fragmented meteoroidSmall rocky or metallic object in orbit around the Sun (or another star).
should all be identical, and therefore, the difference in Fa values between the L impact-melt rock NWA 4150 and the H/L6-NWA pairing group is inconsistent with their pairing.
The 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
isotopic composition of NWA 4150 and its possible pairing group of NWA 4152–4156 will help establish their correct groupings. In addition, K–Ar data will be utilized to provide the age of impact. The photo of NWA 4150 shown above is a 3.21 g end section acquired from Christian Anger which exhibits a ring-shaped, metallic-melt swirl pattern in the upper left corner. Thank you dearly departed friend.