LL Ordinary Chondrites

Northwest Africa 1756

Morocco
Found 2002
Ordinary chondrite (LL3.0/3.2)

NWA 1756. Image © T. E. Bunch.

A 68.2 g meteorite was purchased in Safsaf, October 2002. Classification and mineralogy (T. Bunch and J. Wittke, NAU): monomict chondritic breccia; chondrules are very similar to equivalent chondrules in the LL3.0 Semarkona chondrite in terms of phase/mesostasis compositions, zoning profiles, and textures. Type IA olivine: FeO = 0.21 to 1.94 wt. %; CaO = 0.31 to 0.51 wt. %. Type IIA olivine: FeO = 11.8 to 15.9 wt. %; CaO = 0.10 to 0.19 wt. %, P₂O₅ = 0.09 to 0.36 wt. %. Chondrule mesostasis is optically isotropic. Matrix metal is Ni-rich (50 to 60 wt. %) and occurs in metal-pyrrhotite-haxonite ± magnetite, chromite, carbon, cohenite, 0.1 to 0.2 mm aggregates; metal contains small (<1 μm) SiO₂-rich inclusions. Shock level, S1; one xenolith is S4; weathering grade, W1/W2. Specimens: type specimen, 12.5 g and 2 thin sections, NAU; main mass, Hupé.

NWA 1756. Backscattered electron image of chondrule; note zoned olivine and quenched mesostasis. Photograph © J. H. Wittke, 2003.

Northwest Africa 2095

Northwest Africa
Found 2001
Ordinary chondrite (LL5 melt breccia)

An 8.15 kg single stone with weathered crust was purchased in Rissani, Morocco. Description and classification (T. Bunch and J. Wittke, NAU): exceptional shock-melt LL5 breccia; clasts (up to 8 cm; shock level, S3) have wide, shock-darkened margins (metal melt injections into silicate fractures, S5) that are surrounded by shock-melt glasses with included masses of metal melt spheres (< 0.02 mm, S6). Olivine, Fa_28.0 (FeO/MnO = 54); orthopyroxene, Fs_24.9Wo_2.0 (FeO/MnO = 39 g/g); Plagioclase and maskelynite, An_37.7Or_12.6, Chromite, Cr/(Cr+Al) = 0.865, and metal spheres, Ni = 18.6 to 44.2 wt. % Ni, weathering grade, W2. Specimens: type specimen, 44 g, NAU; main mass, Boswell.

Northwest Africa 2381

Northwest Africa
Purchased 2004 August
Ordinary Chondrite (LL melt breccia)

A 132 g complete and crusted stone was purchased in Erfoud, Morocco. Description and classification (T. Bunch and J. Wittke, NAU): highly shocked (melted and brecciated) LL chondrite (S2-6). Contains sparse marble-shaped (0.8-1.4 mm) LL7 clasts that show equigranular, recrystallized texture with abundant 120° triple grain junctions and no relict chondrules, Olivine, Fa _31.8 (FeO/MnO = 63 g/g); orthopyroxene, Fs_25.1Wo_1.8; chromite, Cr/(Cr+Al) = 0.86, Fe/(Fe+Mg) = 0.92. Clasts are enclosed by a thick mantle (up to 5 mm) of LL chondrite, similar in composition, but without recrystallization (shock level = S3). These mantles are surrounded by highly shocked LL materials that range from complete melt with quench products of olivine, Ca-pyroxenes, and feldspathic glasses (S6) to intense, shock darkened LL clasts (metal melt with injection and maskelynite, S4). Weathering grade is W2. Specimens: type specimen 21 g, NAU; main mass, G. Hupé.

Northwest Africa 2389

Northwest Africa
Purchased July 2004
Ordinary Chondrite (melt breccia with ringwoodite)

A 156 g stone was purchased in Erfoud, Morocco. Description and classification (T. Bunch and J. Wittke, NAU): shocked L5 clasts (S3-4) contain maskelynite, olivine and pyroxenes with planar deformation lamellae and mosaicness, reduced birefringence, localized melt pockets, and isolated shock veins. Clasts are set in partially recrystallized melt with included plentiful, violet to purple ringwoodite grains (<0.25 mm in diameter). Olivine, Fa_25.6; orthopyroxene, Fs_22.8; plagioclase (maskelynite), An_54-94; ringwoodite; FeO = 23.8 wt. %, MgO = 37.5 wt. %, SiO2 = 37.8 wt. %, MnO = 0.30 wt. %. Weathering grade, W2. Specimens: type specimen, 21 g, NAU; main mass, Burkhard.

Northwest Africa 2791

Algeria
Found 2004
LL3-LL4 regolith breccia (with carbonaceous chondrite clasts)

History: A 383 g partially crusted stone was purchased in Erfoud, Morocco.
Petrography: (T. Bunch and J. Wittke, NAU): A regolith breccia of many different lithologies that include LL3.6 and LL4 chondrites, an unknown carbonaceous chondrite, shock-melted clasts and those of unknown petrologic lineage. Matrix consists of plentiful chondrules and fragmental material. Shock characteristics of the clasts range from S2 to S5, weathering grade is W2.
Geochemistry: LL3.6 chondrite olivine = Fa_23-34, FeO/MnO = 50-55 g/g, Cr₂O₃ = 0.0-0.12 wt. %. LL4 olivine = Fa₃₀, FeO/MnO = 55-60. Carbonaceous chondrite olivine = Fa_43.7-54.4, FeO/MnO = 82-93; orthopyroxene = Fs_33-41.5Wo_1.3-2.0; spinel, Fe/(Fe+Mg) = 0.72; FeS, Cr = 0.82 wt. %.
Classification: LL3-LL4 regolithic breccia.
Type specimens: A total of 23.4 g and two thin sections are on deposit at NAU. Mr. Tom Webb is the main mass holder.

NWA 2791. Slice 3.2 cm wide. White clast = impact melt; dark = carbonaceous chondrite; light gray = LL 3.8, medium gray = LL4. Image © T. E. Bunch.

Northwest Africa 3100

Morocco
2003
Ordinary chondrite (LL7)

A 136 g complete stone with weathered crust was purchased in Rissani, Morocco in June 2003. Description and classification (T. Bunch and J. Wittke, NAU): equigranular, fine-grained (avg. diameter, 0.155 mm; range, 0.03 to 0.7 mm), completely recrystallized with no relict chondrules. Mineral modes (vol. %): olivine, 78; orthopyroxene, 10; plagioclase, 5; troilite, 5; metal, 1; chromite and merrilite < 1; olivine greatly enhanced and metal depleted relative to L6 chondrites. Olivine, Fa_28.7 (Fe/Mn = 65.6; orthopyroxene, Fs_23.5Wo_3.1 (Fe/Mn = 48.8; molar FeO/MgO = 0.31 g/g); plagioclase, An_34.1Or_3.1; Ca-rich pyroxene, Fs_12.8Wo₄₁; Ni-rich troilite, Ni = 4.2 wt. %; metal (taenite only), Ni = 20.1 wt. %; chromite, Cr/(Cr+Al) = 0.80, Mg/(Mg+Fe) = 0.21. Shock stage, S1; weathering grade, W2. Specimens: 20.2 g and one thin section, NAU; main mass, Farmer.

Northwest Africa 3127

Northwest Africa
Found 2002
Ordinary chondrite (LL3.1)

NWA 3127. Image © T. E. Bunch.

A 487 g stone was purchased in Safsaf, Morocco in October 2002. Description and classification (T. Bunch and J. Wittke, NAU; J. Grossman, USGS, Reston): polymict chondritic breccia; host is LL3.1 with xenoliths of LL4 and LL5. Chondrules are very similar to the LL3.0 Semarkona and LL3.1 NWA 1756 chondrites in terms of phase and mesostasis compositions, zoning profiles, and textures. FeO contents in 65 type II chondrule olivine cores range from 7.0 to 26.8 wt. % and corresponding CaO from 0.06 to 0.20 wt.%, which are consistent with an LL3.0-3.2 classification (Jones. 1990); Cr₂O₃ contents in these olivines, which is considered to be a more sensitive indicator of petrologic subtype (Grossman, 2004), range from 0.08 wt. % to 0.58 wt. % with an average of 0.38 wt. %, consistent with an LL3.1 classification. Chondrule mesostasis is optically isotropic and SEM imagery shows little unambiguous evidence for metamorphic crystallization of mesostasis glass. Shock level, S2; weathering grade is W3. Specimens: 20.1 g, NAU; main mass Hupé.

Northwest Africa 3335

Algeria
Find: 2005
Ordinary chondrite (LL3.2)

History and physical characteristics: A 2250 g dark brown, heavily stained stone was found in Algeria in 2005 and sold in Rissani, Morocco in 2005.
Petrography: (T. Bunch and J. Wittke, NAU) contains a few shocked dark clasts and several centimeter-sized cream-colored igneous-textured (idiomorphic granular) clasts. These irregular-shaped, olivine pyroxenite clasts contain (vol %): orthopyroxene/clinopyroxene, 56; olivine, 33; mesostasis, 5; diopside, FeS, ilmenite, chromite, and metal, 4. Both clinoenstatite (polysynthetically twinned) and orthopyroxenite are present, crystallographic orientation within the section, notwithstanding. For compositional considerations, they are treated the same.
Mineral compositions: Chondritic host examples: POP chondrule olivine cores (Fa_9–17, FeO/MnO = 47-55 g/g), rims (Fa_26.1–35.8, FeO/MnO = 69-90 g/g). Matrix olivine, Fs_15–35.6; FeO/MnO avg. = 53 g/g; Cr₂O₃ = 0.05–0.45%, mean = 0.12 wt. %. Olivine pyroxenite clasts: orthopyroxene, Fs_0.2-0.7Wo_0.8 (N=27); olivine, Fa_0.7–4.7, FeO/MnO = 15-19 g/g (N=13); diopside, Fs₁Wo₄₂; mesostasis plagioclase, An_96.9; ilmenite, MgO = 5.4 wt. %; chromite, Cr/(Cr+Al) = 0.82; taenite, Ni = 37.8 wt. %.
Classification: Ordinary chondrite (LL3.2). Subtype designation based on olivine heterogeneity and olivine Cr₂O₃ contents.
Type specimen: A total of 20 g is on deposit at PSF who is also the main mass holder.

NWA 3335. Idiomorphic granular clast next to the LL 3.2 host (upper right), base width = 7 mm. Image © T. E. Bunch, 2007.

NWA 3335. Enlarged view of euhedral and subhedral opx and olivine (larger and darker), base width = 3.5 mm. Image © T. E. Bunch, 2007.

Northwest Africa 4549

Western Sahara, Morocco
Find: 2006
Ordinary chondrite (LL3.1)

History and physical characteristics: Collected in Western Sahara, Morocco and purchased by A. Aaronson in Rissani, Morocco in May 2006. A 64 g reddish brown stone with very little fusion crust.
Petrography (T. Bunch and J. Wittke, NAU): A chondrule-rich (76 vol. %) ordinary chondrite with low metal (≤ one vol. %) and several subrounded to subangular poikilitic clasts (1.5- 2.4 mm dia.) of anhedral orthopyroxene host and round olivine inclusions. Low grade weathering with iron staining; shock level is S2.
Mineral compositions: olivine, Fa_8.8-38.0 (FeO/MnO = 28-122, mean, 63); Cr₂O₃ = 0.07–0.34 wt. %, mean, 24; CaO = 0.16–0.54 wt. %). Orthopyroxene. Fs_6.3-27.6. Orthopyroxene oikocrysts, Fs_16.4Wo_2.1 (FeO/MnO = 67); olivine chadacrysts, Fa_28.3 (FeO/MnO = 94).
Oxygen isotopes (D. Rumble, CIW): A cleaned and metal-free sample was analyzed by laser fluorination. Replicate analyses are respectively, δ¹⁷O = 4.100 and 3.800; δ¹⁸O = 6.02 and 5.697; Δ¹⁷O = 0.9315 and 0.8032.
Classification: Ordinary chondrite (LL3.1).
Type specimen: A 8.4 g sample is on deposit at NAU. Mr. A Aaronson holds the main mass.

Other LL Ordinary Chondrites

Photographs of LL Chondrites

NWA 1930. Image © T. E. Bunch, 2004	NWA 1932. Image © T. E. Bunch, 2004
NWA 1933. Image © T. E. Bunch, 2004	NWA 1933. Image © T. E. Bunch, 2004
NWA 1935. LL4. Image © T. E. Bunch, 2003	NWA 1937. Image © T. E. Bunch, 2003
NWA 1946. Image © T. E. Bunch, 2003	NWA 2053. Image © T. E. Bunch, 2004
NWA 2799. (left) PPL image. (right) XPL image. Photomicrographs © T. E. Bunch, 2003