NWA 2627

AcapulcoitePrimitive achondrite that belongs to a small group named after the Acapulco meteorite that was observed to fall in Mexico in 1976. Acapulcoites are made mostly of fine-grained olivine (Fo3-14), orthopyroxene(En86-97), Ca-rich pyroxene (En51Wo44), plagioclase (An12-31), Ni-Fe metal, and troilite. They are transitional between primordial chondritic matter and more differentiated, transitional subgroup
Acapulcoite–LodraniteRare type of primitive achondrite named after the Lodran meteorite that fell in Pakistan in 1868. Initially, lodranites were grouped with the stony-iron meteorites because they contain silicates (olivine, orthopyroxene, and minor plagioclase) and Fe-Ni metal in nearly equal proportions. However, since discovery of the closely related acapulcoite group, lodranites Clan
click on photo for a magnified view Found 2004
no coordinates recorded A 68 g portion of a stone retaining considerable 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. was purchased in Erfoud, Morocco by M. Farmer in October of 2004. A sample was submitted for analysis to Northern Arizona University (T. Bunch and J. Wittke), and NWA 2627 was initially determined to be an anomalous winonaitea partially differentiated asteroid that was disrupted just as it began to form an Fe core and a silicate-rich crust. This disrupting impact mixed silicates into molten Ni-Fe metal forming the silicated IAB irons, and mixed olivine-rich residues of partial melts into unmelted silicates, forming the winonaites. A few winonaites. The stone has a recrystallized texture and is composed of a heterogeneous mixture of 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 (44 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 (41 vol%), FeS (6 vol%), metallic phases (5 vol%), 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 (3 vol%), along with minor abundances of merrillite, Ca-pyroxene, and chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups..

The mineralogy and composition 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 are similar to those for the lodranites, and when plotted on a diagram comparing the Δ17O-isotopic value vs. Fa mol% in olivine (Rumble III et al, 2005), NWA 2627 clearly lies within the acapulcoite field (see Figure 2 plot in LPSC 38, #2254 [2007]). It has been suggested that this meteorite represents a transitional acapulcoite (Touboul et al., 2007) according to the following classification scheme by Floss (2000) and Patzer et al. (2003) based on metamorphicRocks that have recrystallized in a solid state due to changes in temperature, pressure, and chemical environment. stage.

1. primitive acapulcoitesPrimitive achondrite that belongs to a small group named after the Acapulco meteorite that was observed to fall in Mexico in 1976. Acapulcoites are made mostly of fine-grained olivine (Fo3-14), orthopyroxene(En86-97), Ca-rich pyroxene (En51Wo44), plagioclase (An12-31), Ni-Fe metal, and troilite. They are transitional between primordial chondritic matter and more differentiated: near-chondritic (Se >12–13 ppmParts per million (10⁶). [degree of sulfide extraction])
2. typical acapulcoites: Fe–Ni–FeS melting and some loss of sulfide (Se ~5–12 ppm)
3. transitional acapulcoites: sulfide depletion and some loss of plagioclase (Se <5 ppm)
4. lodranites: sulfide, 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, and plagioclase depletion (K <200 ppm [degree of plagioclase extraction])
5. enriched acapulcoites (addition of feldspar-rich melt component)

The high temperatures experienced on the acapulcoite 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., manifest in the recrystallized texture and occasional partial melt phase, suggest that it accreted very early in Solar SystemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids. history when radiogenic 26Al was still extant. This was a time period spanning ~1–3 m.y. after CAISub-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 formation, after the accretionAccumulation of smaller objects into progressively larger bodies in the solar nebula leading to the eventual formation of asteroids, planetesimals and planets. The earliest accretion of the smallest particles was due to Van der Waals and electromagnetic forces. Further accretion continued by relatively low-velocity collisions of smaller bodies in the of differentiated parent bodies had occurred but before the accretion of chondritic parent bodies had begun (Touboul et al., 2007). However, this formation scenario is inconsistent with some acapulcoites having ages younger than that attributed to the complete 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 of radiogenic 26Al. An impact shock heating model has been proposed by Rubin (2007), the details of which can be found on the Monument Draw page.

Data for cooling rates indicate a more rapid cooling for the acapulcoite parent body than that which the bulk H chondriteOrdinary chondrites with a high content of free Ni-Fe metal (15-19 vol. %) and attracted easily to a magnet. Their main minerals are olivine (Fa16-20) and the orthopyroxene bronzite (Fs14.5-18.5), earning them their older name of bronzite chondrites. Chondrules average ~0.3 mm in diameter. Comparison of the reflectance spectra of parent body experienced (but similar to that of H4 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; Kleine et al., 2007), consistent with a smaller acapulcoite parent body and/or a near-surface residence for the acapulcoites. The possibility also exists for a collisional disruption early in its history, forming sub-km- to multi-km-sized fragments, which eventually succumbed to gravitational reassembly. Compared to the lodranite lithological unit, both primitive and typical acapulcoite material is thought to have originated in the outermost layer of the asteroid where it cooled earlier and faster consistent with its older gas retention age, finer-grain size, and less intense metamorphism (<1–3% silicateThe 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 partial meltingAn 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). The lodranites experienced higher degrees of FeNi–FeS melting as well as silicate partial melting (~5–20%), with loss of an FeS and a basaltic component. The transitional acapulcoites exhibit features (e.g., HSE-rich metal) consistent with extensive melting of metal and sulfide phases, including melt migration and pooling, representing a continuum between the formation of acapulcoites and lodranites, or alternatively, representing formation at greater depths associated with 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. formation (Dhaliwal et al., 2017). For more complete amd current formation scenarios of the acapulcoite–lodranite parent body, visit the Lodran page.

Northwest Africa 2627 has been weathered to grade W2/3 and has been shocked to stage S2. The 210 g acapulcoite NWA 4399 might be paired. The photo of NWA 2627 above is a 0.88 g partial slice, photographed by Jim Strope.