Martian Igneous stony meteorite with a Martian origin consisting mainly of plagioclase (or a shocked glass of plagioclase composition) and pyroxene. They are the most abundant type of SNC meteorites and the type member is the Shergotty meteorite, which fell in India in 1865. Shergottites are igneous rocks of volcanic or Click on Term to Read More
(enriched, permafric, Oxidation 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)
Found April 2001
no coordinates recorded One large mass of 522 g along with twenty-two additional fragments, all together weighing 576.77 g, were found by a French team in the Maarir region near the border of Morocco and Algeria. This Work 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 designated Northwest Africa 1068, and a sample was submitted to École Normale Supérieure de Lyon and other institutions for analysis and classification. Unaware of the analyses being conducted by the French institutions, additional paired fragments purchased in Morocco having a combined weight of 118 g were submitted to the University of Washington (Irving and Kuehner, 2002). Since the name NWA 1110 had been previously reserved from the Nomenclature Committee for these additional fragments, this meteorite will be recognized as a pairing under both names. Subsequent to this, other individual fragments were recovered in the strewnfield, some of which were submitted to the NomCom under unique NWA numbers (e.g., NWA 1183, NWA 1775, NWA 2373, NWA 2969).
Following their crystallization at depth, the cumulate olivine megacrysts were incorporated into an ascending, enriched, oxidized magma plume that originated at the upper-mantle (at depths of ~250–400 km; Kiefer, 2003), envisioned to be similar to lunar ur-KREEP that crystallized as a late-stage residual liquid of the martian Completely 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 (Borg et al., 2012). The magma ponded in or near the base of the crust where olivine crystallized and accumulated from either the same (phenocrysts or antecrysts) or neighboring (xenocrysts) magma plumes. Low-Ti/Al pyroxene then crystallized and erupted onto or near the surface together with the olivine megacrysts. Cooling occurred rapidly close to the surface where shock Rocks that have recrystallized in a solid state due to changes in temperature, pressure, and chemical environment. Click on Term to Read More effects became significant. This scenario is consistent with the finding that NWA 1068 has a REE pattern that is similar to other basaltic shergottites, while other olivine-containing shergottites such as DaG 476, Dhofar 019, and SaU 005 do not. Xenocrystic olivines in EETA79001A might have a similar origin. Northwest Africa 1068 is a relatively primitive shergottite with a magnesian bulk composition, but is not as magnesian as experiments indicate it should be if it represented a primary liquid composition. Because it has incorporated a high abundance of olivine megacrysts it no longer represents a primary magma composition (Bunch et al., 2009).
Trace element data confirm that Northwest Africa 1068/1110 is unpaired with any previously found martian meteorites. In contrast to the depleted LREE evident in most all other olivine-phyric shergottites, NWA 1068 is enriched in incompatible elements similar to that which is found in the basaltic shergottites Shergotty, Zagami, and Los Angeles; incompatible element ratios are consistent with these basaltic shergottites as well. This suggests a parental magma for NWA 1068 of basaltic shergottite composition which had assimilated a late-stage, enriched, and more-oxidized cumulate component close to lherzolitic composition. Thereafter, olivine crystallized and was accumulated, perhaps as phenocrysts (Shearer et al., 2008). Studies of NWA 1068 have continued in an effort to characterize the true nature of the olivine megacrysts and to better resolve the petrogenesis of the meteorite. Through advanced Fe–Mg One 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 and major, minor, and trace element analyses of NWA 1068 bulk rock and olivine megacrysts, Collinet et al., (2017) determined that the meteorite is most consistent with a near-primary magma composition. In their formation model the olivine megacrysts and the groundmass of the meteorite are co-genetic. Subsequent to olivine megacryst formation, which they ascertained occurred over a time period of ~2–6 years under relatively slow cooling conditions within a deep Geology: 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 (the final span of ~100 days involved rim and groundmass crystallization at much faster cooling rates during/after magma ascent), the megacryst cores experienced simultaneous diffusion and growth of outer rims along with crystallization of the groundmass pyroxene and olivine, as evidenced by the fractionated Fe–Mg isotope and element profiles which are observed. This diffusion process Oxidation 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 the Fo content by ~3.2 mol% from its original value to values as magnesian as Fo77; these current Fo values had previously been attributed to Fe–Mg equilibrium conditions attained through olivine accumulation. Therefore, the bulk rock composition of NWA 1068, and in a similar way that of LAR 06319, is likely representative of a primary magma, derived from a refractory mantle source, having an intermediate composition of at least ~Fo80 (see diagram below).
Diagram credit: Collinet et al., GCA, vol. 207, p. 294 (2017)
‘Crystallization history of enriched shergottites from Fe and Mg isotope fractionation in olivine megacrysts’
(https://doi.org/10.1016/j.gca.2017.03.029) Isotopic analyses using Sm–Nd and Rb–Sr data have determined a crystallization age for this shergottite of 185 (±11) m.y., and its CRE age has been calculated to be 2.2 (±0.2) m.y. (2.5–3.1 m.y. based on 10Be [Nishiizumi and Caffee, 2006] and 2.0 ±0.5 m.y. based on Ar systematics [Walton et al., 2007]). This CRE age is similar to several other martian meteorites, including NWA 2646, LAR 06319, and NWA 480/1460. Cosmic ray exposure ages have now been determined for many martian meteorites, and Mahajan (2015, #1166) compiled a chart based on the reported CRE ages for 53 of them. He concluded that together these 53 meteorites represent 10 distinct impact events which occurred 0.92 m.y., 2.12 m.y., 2.77 m.y., 4.05 m.y., 7.3 m.y., 9.6 m.y., 11.07 m.y., 12.27 m.y., 15 m.y., and 16.73 m.y. (see his chart here). It was argued that NWA 1068/1110 was launched from Mars during the 2.12 m.y.-old impact event. In a subsequent review based on multiple criteria, Irving et al. (2017, #2068) made a new determination of the number of separate launch events associated with the known (101 at the time of their study) martian meteorites. They speculate that the number could be as few as twenty, and suggest that NWA 1068/1110 might have been ejected with the large group of at least 26 enriched shergottites, or alternatively, it could represent a unique ejection event because of its disparate texture. Interestingly, a determination of the Pb-isotopic composition of the original source of the olivine-phyric shergottites shows a similar plot to that of the nakhlites, and these diverse martian meteorites may have originated from the same mantle reservoir (Emil et al., 2006). The specimen of NWA 1068 pictured above is a 1.19 g partial slice with a thin black impact-shock vein along the left side and a natural edge along two sides. The photo below shows the Largest 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 of NWA 1068.
∗ Recent geochemical research on the martian basalts has led to new petrogenetic models and classification schemes.read more >>
Photo courtesy of B. Fectay and C. Bidaut—Meteorite.fr