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Lunar Meteorite: Paired Anoual and Northwest Africa stones 773, 2700, 2727, 2977, 3160, (3186 provisional), and 3333northwestern Africa |
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Photo of a sawn face of NWA 773 (from Fagan et al., 2003; photo by Marvin Killgore). As with Dhofar 287, the stone appears to be a portion of a regolith breccia that contains a large clast of cumulate olivine gabbro and many small clasts. Click on image for enlargement. |
 A slice of NWA 2977, which, like NWA 773, is a cumulate olivine gabbro. Tick marks on the scale are spaced at 1 mm intervals. (Photo by Randy Korotev)  Sawn face of NWA 2727 showing three lithologies: (1) basalt (right) and (2) breccia (left) containing (3) two gabbro clasts including a very coarse-grained one. (Photo courtesy of Stan Turecki and Tony Irving)
Two views of a slice of NWA 2727, a
breccia that is dominated by mare basalt.
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Why Do We Think These Stones Are All Paired?
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from The
Meteoritical Bulletin, No. 85, Meteoritics & Planetary Science
36, A293-A322 (2001)
Northwest Africa 773~26°46'N ~12°49'WWestern Sahara Found 2000 September Lunar Meteorite (cumulate olivine norite with regolith breccia) [see discussion below regarding classification] Three stones of 359 g, 224 g and 50 g, totaling 633 g were sold to Marvin Killgore (SWML) by nomads who showed him the place of find on a flat dry desert plain near Dchira, Western Sahara. Mineralogy and classification (T. Fagan, UHaw, M. Killgore, SWML): consists of two distinct lithologies, cumulate rock and regolith breccia; weathering grade, W1; shock stage, S5. Cumulate portion: modes (vol%) are olivine = 54.7, pigeonite = 24.2, augite = 5, feldspar (including minor K-feldspar) = 15.6, opaques (troilite, chromite, Fe-metal) = 0.5; olivine, Fa28-97, mean Fa31, FeO/MnO = 99±11 g/g; pigeonite, En64Wo11, FeO/MnO = 53±6 g/g; augite, En49Wo36, FeO/MnO = 46±6 g/g; plagioclase, An88-91; Ba-rich K-feldspar, An3Ab4Or93 with average BaO = 2.2 wt.%. Breccia portion: contains fragments of cumulate portion as well as silica glass, hedenbergitic pyroxene, volcanic rocks, and unusual lithic clasts with fayalite + Ba-rich K- feldspar + silica + plagioclase; olivine and pyroxene in the breccia have a slightly wider compositional range towards lower Mg/(Mg+Fe) than in the cumulate portion of the rock. Chemical composition (D. Mittlefehldt, JSC): KREEP-rich with strong negative Eu-anomaly. Noble gases (O. Eugster, Physikalisches Institut, Bern): high solar wind component, 4He/20Ne = 9, indicative of regolith material. Specimens: type specimen, 15 g, NHM; main mass SWML. |
from The Meteoritical Bulletin, no. 90, Meteoritics & Planetary
Science 41, 1383-1418 (2006)
Northwest Africa 2700MoroccoFind: 2004 Achondrite (lunar, olivine gabbro with regolith breccia) History: A light green to dark complete stone of 31.7 g was purchased in Erfoud, Morocco, in November 2004. Petrography and Geochemistry: (T. Bunch and J. Wittke, NAU) The specimen consists of olivine gabbro and regolith breccia lithologies. The cumulate olivine gabbro contains ~50 vol% olivine (Fa29.3-34.7; FeO/MnO = 94), pigeonite (Fs22-28.3Wo5.6-10; FeO/MnO = 52), augite (Fs13.2Wo38.5), plagioclase and minor maskelynite (An89), Ba-rich alkali feldspar (Or92An4; BaO = 8.9 wt%), Cr-spinel, ilmenite, phosphate, and troilite. The breccia lithology is dominated by small olivine gabbro fragments and also contains subvariolitic basalt clasts with zoned pyroxenes (Fs44Wo29 to Fs58Wo23; FeO/MnO = 57); plagioclase (An90); ilmenite, and Fe-rich, low-Ca pyroxene (Fs80.8Wo14); symplectites of fayalite (Fa91); hedenbergite (Fs60.3Wo32.7); silica; clear to yellow glass spherules; agglutinates, high silica fayalitic rocks (Fa95.6); ulvöspinel; K2O-rich glass (K2O = 8.8; SiO2 = 77 [both wt%]), and pure SiO2. Classification: Achondrite (lunar, olivine gabbro with regolith breccia) where the olivine gabbro is moderately shocked and minimally weathered. Note: This sample may be paired with NWA 773. Specimens: A 6.8 g type specimen and two thin sections are on deposit at NAU. An anonymous finder holds the main mass. |
from The Meteoritical Bulletin, no. 90, Meteoritics
& Planetary Science 41, 1383-1418 (2006)
Northwest Africa 2727Morocco or AlgeriaFind: June/July 2005 Achondrite (Lunar mare basalt/gabbro breccia) History: Four stones of 30.6 g, 11.6 g, 64 g and 85 g were purchased from Moroccan dealers in Erfoud for a consortium of North American collectors in June and July of 2005. Petrography and Geochemistry: (T. Bunch and J. Wittke, NAU; A. Irving and S. Kuehner, UWS; R. Korotev, WUSL) All stones are very similar and consist of a clast-dominated polymict breccias composed of >80 vol% olivine-phyric basalt and gabbroic/diabasic clasts (0.2 cm to several cm across) within a finer breccia matrix. The basalt clasts show a wide range in mineral compositions, but all contain phenocrysts of olivine Fa 28-99 FeO/MnO = 98.9 and some also have phenocrysts of pyroxferroite or chromite all in a rapidly quenched, fine-grained matrix consisting of intergrown pigeonite, pyroxferroite, K-Ba-feldspar, ilmenite, merrillite, baddeleyite, troilite, silica and glass. The gabbroic clasts range in texture from coarser grained (>3 mm) hypidiomorphic gabbro to finer grained (~1 mm) diabasic clasts. Both types of gabbroic lithologies consist mainly of pigeonite Fs23.3-31.3Wo8.7-11.5, FeO/MnO = 60-69 and subhedral to anhedral olivine Fa34.1-41 FeO/MnO = 85-99 with less abundant augite Fs24.1-47.5 Wo24.4-32.1 and partly maskelynitized, blocky to tabular plagioclase An81-94. The breccia matrix consists mainly of gabbroic debris with fragments of basalt, silica polymorph, symplectites, subparallel intergrowths of anorthite + pyroxferroite+ilmenite and shock-melted material. Bulk compositions: (R. Korotev, WUSL) INAA of 11 subsamples show that they vary considerably in bulk composition, with the most Fe-rich subsample nearly indistinguishable from NWA 3160 basalt. All other subsamples are compositionally equivalent to mixtures of NWA 3160 basalt and the regolith breccia lithology of NWA 773, but with slightly lower concentrations of incompatible elements. Note: Based on petrography, mineral compositions, and bulk compositions, these stones are paired with NWA 3160 and may be paired with NWA 773. Classification: Achondrite (lunar, mare basalt/gabbro breccia). Specimens: A 20.2 g type specimen and two polished thin sections are on deposit at NAU. A 0.5 g type specimen is on deposit at WUSL. Oakes, Reed, Boswell, and Turecki hold the main masses. |
from The Meteoritical
Bulletin, no. 90, Meteoritics & Planetary Science 41,
1383-1418 (2006)
Northwest Africa 2977Morocco or AlgeriaFind: 2005 November Achondrite (lunar, gabbro) History: A single minimally weathered fusion-encrusted stone of 233 g was purchased from a Moroccan dealer in Tagounite, Morocco, by M. Farmer in November 2005. Petrography and Geochemistry: (J. Wittke and T. Bunch, NAU; A. Irving, UWS) The specimen consists of a single yellow-green, relatively coarse-grained rock traversed by thin, black glass-rich veins. It is an olivine-rich, twopyroxene cumulate gabbro composed of olivine (Fa31.7; FeO/MnO = 96; 52 vol%), (Fs26.6Wo6.7; 23 vol%), augite (Fs16.2Wo29; 9 vol%), and plagioclase (An56; 14 vol%) with minor amounts of Ba-K feldspar, chromite, ilmenite, and merrillite. Larger pigeonite grains commonly enclose equant olivine grains, which contain abundant melt inclusions (0.025–0.125 mm). Plagioclase is partially converted to maskelynite, and pyroxenes and olivine exhibit shock lamellae and undulatory extinction. Note: This specimen is identical in texture and mineral composition to the gabbro clasts in NWA 773 and NWA 2700 and thus appears to be paired with those breccia specimens. Classification: Achondrite (lunar, gabbro); minimal weathering. Specimens: A 20.1 g type specimen and one polished thin section are on deposit at NAU. A 0.5 g specimen is on deposit at WUSL. An anonymous owner holds the main mass. |
from The
Meteoritical Bulletin, no. 90, Meteoritics & Planetary Science 41,
1383-1418 (2006)
Northwest Africa 3160MoroccoFind: July 2005 Achondrite (lunar mare basalt breccia) History: In July 2005, A. and G. Hupé purchased three broken stones with a total weight of 34 g from a Moroccan dealer in Erfoud, Morocco. Physical Characteristics: The largest stone (28 g) has a partial thin weathered fusion crust. Petrography: (R. Zeigler and R. Korotev, WUSL; A. Irving and S. Kuehner, UWS) The large specimen consists almost entirely of a fine-grained, olivine-phyric basalt clast with minor attached breccia matrix and appears to be part of a larger, coarse-grained, polygenic breccia. The two small stones are pieces of the breccia. The basalt contains phenocrysts of euhedral to subhedral olivine (~0.1–0.9 mm) and minor chromite (<0.1 mm). Geochemistry: Olivine phenocrysts are zoned, with cores typically Fo55-70 and rims extending to ~Fo40; FeO/MnO ratios are 91-105. The groundmass has spinifex olivine Fo29 and skeletal pyroxene En37-39Wo11-13 FeO/MnO = 71-75 set in a fine-grained matrix of pyroxene En35-39Wo20-23, olivine ~Fo22 and glass. The breccia lithology is a fragmental breccia consisting primarily of olivine Fo6-82 and pyroxene En1-68Wo9-39Fs16-83, with minor amounts of plagioclase An82-97 and trace silica; hedenbergite-fayalite-silica symplectite (after former pyroxferroite), and Fe-Ti-Cr oxides. Classification: Achondrite (lunar, mare basalt breccia). Note: These samples may be paired with NWA 2727. Specimens: A 4.8 g type specimen and one polished thin section are on deposit at UWS. A 2.1 g specimen is on deposit at WUSL. A. Hupé holds the main mass. |
from The
Meteoritical Bulletin, No. 94, September 2008. Meteoritics & Planetary
Science 43, 1551–1588 (2008). Northwest Africa 3333MoroccoPurchased 2005 May Achondrite (lunar basaltic fragmental breccia) History: Fabien Kuntz purchased a 33 g specimen from a Moroccan dealer. The original main mass was broken into at least 5 pieces and distributed to several dealers.. Physical characteristics: A partially weathered blackish brown fusion crust was present on the specimen. Cut and polished surfaces on two different specimens reveal a coarsely brecciated texture, while a third specimen exhibits three different lithologies. Petrography: (R. Zeigler, WUSL) The specimen examined consists of one basalt clast (1.5 cm) and one clast of cumulus olivine gabbro (1.2 cm) set in a fragmental breccia matrix. The basalt consists of large phenocrysts of zoned olivine and smaller chromite phenocrysts set in a fine-grained matrix of spinifex olivine, skeletal pyroxene, and glass. The olivine gabbro is 50% olivine, 35% pyroxene, and 15% plagioclase. A vein of black shock melt separates the cumulate clast from the fragmental breccia. The breccia is composed predominantly of pyroxene and olivine clasts, with minor plagioclase, and trace silica, Fe,Ti,Cr oxides, troilite, chromite, ilmenite, FeNi, apatite, and RE-merrillite. Mineral compositions and geochemistry: Matrix pyroxene and olivine is Fs17-65Wo12-29En8–61 and Fo5-60; plagioclase clasts are An86-95Or<2. Olivine in the basalt is zoned (Fo47-72). Mineral compositions in the olivine cumulate are Fo68, Fs63Wo15 and Fs52Wo32, and An92Or1. Fe/Mn = 85–110 (olivine) and 40–77 (pyroxene). Bulk composition: (R. Zeigler and R. Korotev, WUSL) The basalt (TiO2 = 0.8%, FeO = 21%, MgO= 14%, Th = 1.4 µg/g) is compositionally similar to that of NWA 3160; the cumulate olivine gabbro (TiO2 = 0.4%, FeO = 20%, MgO = 27%, Th = 1.2 µg/g) is similar to NWA 773 and NWA 2977. All lithologies are characterized by low concentrations of Na2O (= 0.15 ± 0.06 %) and Eu (= 0.4 ± 0.2 ppm) compared to other lunar basalts. The oxygen isotope composition (I. A. Franchi, OU) is consistent with lunar origin (δ17O=2.94, δ18O=5.59, Δ17O = 0.032). Classification: Achondrite (lunar basaltic fragmental breccia). The specimen is another stone of the NWA 773/2700/2727/2977/3160 pair group. Type specimens: A mass of 6.55 g is on deposit at DuPont and 0.4 g (neutron irradiated) and one thin section at WUSL. |
from The
Meteoritical Bulletin,
no. 93, Meteoritics & Planetary
Science 43, 571-632 (2007)AnoualAnoual, Morocco 32°44´4.5?N, 2°57´28.7?WFind: 3 May 2006 Achondrite (Lunar, mare basalt/gabbro breccia) History: Nomads from near Anoual (a village located in the East of Morocco between Bouarfa and Talsint; about 40 km E-N-E of the latter) learned that the small odd stones that had been found close to their settlement in June and July of 2005 was indeed a meteorite from the Moon (NWA 2727). After extensive searching and screening of the soil, Mr. Boujena recovered 12 pieces for a total mass of 5.92 g, over a small area of about 5 m in diameter. The small size of the pieces can be explained by the brecciated character of the stone. Ph. Thomas visited the place in May 2006 and May 2007, participated in the search, took pictures, in particular of the investigated soil and registered the GPS coordinates. Physical characteristics: Tan greenish stones devoid of fusion crust. Petrography: (A. Jambon, O. Boudouma and D. Badia. UPVI). Breccia composed dominantly of two lithologies: A phyric basalt and a gabbro. Basalt with subhedral olivine phenocrysts (<1mm; 20 vol%) slightly resorbed in a finely crystallized groundmass. Highly fractured gabbro clasts. Small doleritic clasts with zoned pyroxenes. Mafic areas of once molten rock with olivine needles. One clast of quenched basaltic melt with numerous zirconolite needles (0.7 vol%; 0.1 mm) silica and celsian K-spar. Ilmenite, troilite, chromite. Plagioclase and clinopyroxene. Carbonate fills the largest fractures. Geochemistry: (EMPA) Olivine (Fa45-28, with few crystals >Fa45; FeO/MnO = 97). Pyroxene: from (Mg#= 0.80) pigeonite (Wo10) and augite (Wo45) to pyroxferroite (Fs70Wo25; FeO/MnO = 70). Plagioclase (An91-83). Spinel (Cr66Sp25Us3Mt6). Classification: Lunar mare basalt/gabbro breccia. Paired with NWA 2727/3160 (and potentially NWA 3333) Type specimens: A total of 1.205 g of sample (one polished section) is on deposit at UPVI. Thomas holds the main mass. |
| Modal
Mineralogy of Northwest Africa 773 Cumulate Portion (values in percent) |
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| Met.Bull. | Fagan et al. | Jolliff et al. | Bridges et al. | |
| olivine | 55 | 55.5 | 48 | 66 |
| augite | 5 | 8.7 | 12 | 26 |
| pigeonite | 24 | 18.9 | 28 | |
| hypersthene | 2 | |||
| plagioclase | 15 | 14.2 | 10 | 8 |
| alkali feldspar | minor | 1.6 | trace | |
| ilmenite, chromite, alkali feldspar, phosphates, troilite, FeNi metal | <1 | <1.5 | <1 | <1 |
| The cumulate is coarse grained and the thin sections are small, so the modal mineral proportions obtained from different sections do not agree well. Because augite and pigeonite, both clinopyroxenes, dominate over orthopyroxene, which is at most "minor" (Korotev et al., 2002), the cumulate is a gabbro, not a norite. Specifically, it is an olivine gabbro because olivine exceeds 10%. If plagioclase is actually <10%, then it's a peridotite. | ||||
After Stöffler et al. (1980) |
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