Lunar MaficOne of the two broad categories of silicate minerals, the other being felsic, based on its magnesium (Mg) and/or iron (Fe) content. Mafic indicates silicate minerals that are predominantly comprised of Mg and/or Fe.The term is derived from those major constituents: Magnesium + Ferrum (Latin for iron) + ic (having, Th-rich, Impact-Melt 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 (KREEP-melt regolithMixture of unconsolidated rocky fragments, soil, dust and other fine granular particles blanketing the surface of a body lacking an atmosphere. Regolith is the product of "gardening" by repeated meteorite impacts, and thermal processes (such as repeated heating and cooling cycles). breccia)
Found Summer of 2006 no coordinates recorded Two paired stones weighing 64.3 g (NWA 4472) and 188 g (NWA 4485) were found in the Algerian desert and subsequently purchased by separate collectors (G. Hupé and S. Ralew, respectively). A portion of each was submitted for analysis to the University of Washington in Seattle (S. Kuehner and A. Irving) and Washington University in St. Louis (R. Korotev), and the 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 was classified as a unique KREEP-rich, basaltic melt breccia.
This is a polymict brecciaGeneral term for all breccias that are neither monomict nor dimict. Modified from image source: http://www.saharamet.com/meteorite/gallery/HED/index.html. composed of clasts from diverse lunar locations including mareBroad low plains surrounded by basin-forming mountains, originally thought to be a sea (pl. maria). This term is applied to the basalt-filled impact basins common on the face of the Moon visible from Earth. 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, High-Mg Suite (HMS), High-Alkali Suite (HAS), ferroan anorthositeA phaneritic, intrusive igneous rock made with a modal composition (i.e. volume%) > 90% plagioclase feldspar of undefined composition (anorthitic to albitic, or combination thereof), and a small mafic component between 0 - 10% such as pyroxene, ilmenite, magnetite, and olivine 1. The name anorthosite is derived from the calcium-rich (FAN), and impact-melt lithologies dispersed in the matrixFine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents.. The KREEP-bearing assemblages are composed of granophyric textured clasts consisting of intergrowths of silicaSilicon dioxide, SiO2. and K-feldspar, together with the high-temperature 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 zirconium oxide, or baddeleyiteA rare zirconium oxide (ZrO2) mineral, often formed as a shock-induced breakdown product of zircon. This mineral can be found in some lunar and martian meteorites., and the Fe(Zr,Y)Ti-silicate known as tranquillityite, a mineral first recognized as a late-stage fractional crystallizationA crystallization process in which minerals crystallizing from a magma are isolated from contact with the liquid. It is a key process in the formation of igneous rocks during the process of magmatic differentiation. Also known as crystal fractionation. product in Apollo 11 and 12 basalts. Other mineral fragments identified in NWA 4485 include 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, 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 category., 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, 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, chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups., K-feldspar, apatite, merrillite, silica, Fe-metal, and FeS, most reflecting derivation from a KREEP-rich precursor magmaMolten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. (Arai et al., 2009) referred to as urKREEP. The investigators observed that some of these KREEPLunar igneous rock rich in potassium (K), rare-earth elements (REE), phosphorus (P), thorium, and other incompatible elements. These elements are not incorporated into common rock-forming minerals during magma crystallization, and become enriched in the residual magma and the rocks that ultimately crystallize from it. basalt clasts exhibit chemical zoning and thick exsolutionSegregation, during cooling, of a homogeneous solid solution into two or more different solids. lamellae, attesting to slower cooling conditions at a deeper location compared to the Apollo mare basalts. The matrix also contains a variety of glasses, some containing vesicles and others taking the form of spherules enriched in P and K. In their study of apatite grains in NWA 4472, the pairing to NWA 4485, Tartèse et al. (2014) found that they contain moderate amounts of water, in the range of 2,000–6,000 ppmParts per million (106).. Associated isotopic studies on the apatite demonstrated elevated δ37Cl values compared to terrestrial values, which suggests this meteorite has retained its original lunar isotopic signature. Moreover, they recognized that the δD values are consistent with lunar rocks associated with HMS, HAS, and KREEP-rich basalts.
The bulk composition of NWA 4485 reflects a high REEOften abbreviated as “REE”, these 16 elements include (preceded by their atomic numbers): 21 scandium (Sc), 39 Yttrium (Y) and the 14 elements that comprise the lanthanides excluding 61 Promethium, an extremely rare and radioactive element. These elements show closely related geochemical behaviors associated with their filled 4f atomic orbital. abundance with a strong negative Eu anomaly, with overall incompatible 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 abundances in the range of the only known KREEP-rich lunaites—the impact-melt breccias Sayh al Uhaymir 169 and Dhofar 1442. SaU 169 contains ~4.0 b.y. old clasts containing very high-K KREEP which best reflect the composition of primordial urKREEP (Lin et al. 2010). Basaltic clasts in NWA 4472/4485 sample low-Ti to very low-Ti source regions and exhibit a range of metamorphicRocks that have recrystallized in a solid state due to changes in temperature, pressure, and chemical environment. textures. Some of these are fayalite-rich, quenched-textured glass thought to be derived from impact melting of mare basalt lithologies. Also present are a variety of feldspathic impact-melt, fragmental, and granulitic breccias, as well as 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 clasts and glass spherules, all consistent with lithification within the lunar regolith.
The composition of NWA 4472/4485 is similar to that of the Th-rich, mafic, LKFM (low-K Fra Mauro) impact-melt breccias recognized from the Apollo collection; specifically, group-C melt breccias of Apollo 15, group-1S melt breccias of Apollo 16, and the aphanitic and poikilitic impact-melt breccias of Apollo 17 (Korotev 2000). The four constituents of the LKFM material—KREEP noriteIgneous rock composed of 90% plagioclase, 95% orthopyroxene (low-Ca pyroxene) and less than 10% olivine. Norite is most commonly found in the lunar (highlands) meteorites but has also been found in about a dozen diogenites, a few shergottites, and a very small number of other achondrite types. Gabbro is very, forsteritic dunite, feldspathic upper 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, and FeNi-metal—are thought to be the likely products of a basin-sized impact into the ancient ‘Great Lunar Hot Spot’, which created the Imbrium basin within the Th-rich Procellarum KREEP Terrane (PKT) (Korotev, 1999). The impactor is thought to have been an iron meteoriteMeteorite composed mainly of iron (Fe) and nickel (Ni) in the form of two alloys, kamacite and taenite. Due to their metallic makeup and extraordinary weight, iron meteorites are easily distinguished from ordinary rocks. Also, because they rarely break up in the air and suffer much less from the effects that mixed upper 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 dunite with KREEP-contaminated Mg-rich magma, and incorporated clasts of ferroan anorthositic upper crust. The LKFM composition is unique to the PKT, and with its high FeO (noritic) composition and incompatible element abundances (>10 ppm Sm; 5.9–7.9 ppm Th), NWA 4472/4485 is likely derived from this nearside region (Joy et al., 2008). Other possible source locations are northwest of Sinus Iridium within the Jura mountains, northwest of Sinus Roris at Herschel 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., regions of the MonsLarge area of high relief; mountain (pl. montes). Alpes formation in western Mare Imbrium, regions of the Apennine mountains near Mons Caucasus and Mons Bradley near Apollo 15, and regions near the craters Ptolemaeus and Lalande, the latter suggested to be the source location of SaU 169.
Calzada-Diaz et al. (2015) compared compositional and age data from a large number of lunar meteoritesAchondrite meteorites from the surface of the Moon. Most were found in the hot deserts of northern Africa and Oman and others were found in the cold desert of Antarctica, although one, a 19-gram specimen, was recovered in 1990 from Calcalong Creek, Australia. These stones are of great importance because, with elemental remote sensing data obtained by the Lunar Prospector gamma rayMost energetic form of radiation, similar to x-rays and light, except with shorter wavelengths (<0.01 nm) and higher energies (>105 eV). Despite their high energies and penetrating power, g-rays from cosmic sources are absorbed by the atmosphere. In nuclear reactions, decay by g-ray emission permits an excited nucleus drop lower spectrometer, primarily for Fe, Ti, and Th, to better constrain the meteorite’s source regions. For the KREEP-rich basaltic melt breccia NWA 4485/4472, plausible ejection sites were identified near the John Herschel crater and in Mons Caucasus, having a composition consistent with ejectaFractured and/or molten rocky debris thrown out of a crater during a meteorite impact event, or, alternatively, material, including ash, lapilli, and bombs, erupted from a volcano. from the Imbrium basin (see image below). Image credit: A. Calzada-Diaz et al. MAPS, vol. 50, #2, p. 220 (2015) ‘Constraining the source regions of lunar meteorites using orbital geochemical data’ (http://dx.doi.org/10.1111/maps.12412) Establishment of a thorough chronological history of this lunar rock following the initial basin-forming impact, and including the time spent on the lunar surface, in Moon–Earth transitWhen a small celestial body moves in front of a much larger one (as when Mercury or Venus appears in silhouette against the solar disk or when a satellite passes in front of Jupiter or Saturn). The shadow of a satellite may also transit the disk of its primary., and in terrestrial residence has begun (Joy et al., 2009). Cosmogenic Ar–Ar data are indicative of a ~300 m.y. near-surface residence as part of the ancient lunar regolith. The Pb–Pb and U–Pb ages were calculated from the phosphates fluorapatite and merrillite in matrix and basalt clasts, as well as from zirconOrthosilicate mineral, Zr(SiO4), observed in all terrestrial rocks type and in ordinary chondrites, eucrites, mesosiderites, and lunar rocks. grains in the KREEP basalt component (Joy et al., 2011). The ages found within this regolith breccia reflect a diversity of lithic fragments with a wide range of crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. ages (~4.35–3.94 b.y.); the younger ages in this range are consistent with those of Apollo KREEPy mare basalts possibly dating the formation of Mare Imbrium, while the oldest ages were derived from a matrix apatite grain and might reflect the crystallization of the HAS lithology. The lower Ar–Ar apparent age of 1.7–2.2 b.y. obtained for trapped solar windSupersonic flow of high-speed charged particles continuously blowing off a star (mostly e- and p+). When originating from stars other than the Sun, it is sometimes called a "stellar" wind. The solar wind may be viewed as an extension of the corona into interplanetary space. The solar wind emanates radially Ar is thought to reflect a recent impact-resetting event which could represent the consolidation of the NWA 4472/4485 meteorite components.
A more thorough treatment of the chemical classification of lunar meteorites can be found on the WUSL—Lunar Meteorites website, including information on the other (unpaired) KREEP-rich meteorites SaU 169 and Dhofar 961/960/925/SaU 449, the KREEPy clastA mineral or rock fragment embedded in another rock. bearing meteorites Calcalong Creek and Y-983885, and the KREEP basalt meteorites comprising the NWA 733 pairing group, the LAP pairing group, and Dhofar 287a.
NWA 4472/4485 contains Sr and Ba indicative of terrestrial weathering. Both portions of the meteorite also contain high Br concentrations, suggesting that they were contaminated by seawater. The photo of NWA 4485 shown above is a 0.32 g partial slice, while that pictured below is the uncut mass as found (both photos courtesy of Chladni’s-Heirs.com).
Photo courtesy of Chladni’s-Heirs.com