CK Carbonaceous Chondrites

Dhofar 1430 (18°34'10"N 54°14'24"E)

Oman
Find: March 06, 2006
Carbonaceous chondrite (CK3)

History and physical characteristics: A 185 g complete, poorly crusted stone was found in the Dhofar region by M. Farmer and R. Ward March 06, 2006.
Petrography: (J. Wittke and T. Bunch, NAU) Greenish gray stone that has a poorly crystallized matrix of olivine, augite, plagioclase, feldspathic glasses, orthopyroxene, Cr-magnetite, ilmenite, pyrite, pyrrhotite, and pentlandite. Contains many heavily mantled chondrules (up to 1.4 mm in dia.), compound chondrules, relict dusty olivine grains within porphyritic chondrules, single crystals of zoned olivine (0.3-0.85 mm in dia.) and poorly crystallized, plagioclase-rich objects.
Mineral compositions and geochemistry: Matrix olivine (Fa_29.3-34.5, NiO = 0.78 wt %, FeO/MnO = 95-133 g/g); orthopyroxene (Fs_23.3Wo_2.3); augite (Fs₁₂Wo_24.3); plagioclase/feldspathic glasses (An_38-78) and Cr-magnetite (Cr₂O₃ = up to 6.6 wt %).
Classification: CK3 carbonaceous chondrite., light to moderately weathered and lightly shocked (S2).
Type specimens: A sample of 20.1 g is on deposit at NAU. Robert Ward is the main mass holder.

Northwest Africa 772 (26°26.96' N, 11°41.61' W)

Morocco
Found October 2000
Carbonaceous chondrite (CK3)

A 71 g crusted stone was found southwest of Raudat Haua by a person prospecting for meteorites. Mineralogy and classification (T. Bunch and J. Wittke, NAU): modes (vol. %) are matrix = 58, chondrules = 32, sulfides = 7, Cr-magnetite = 2, refractory inclusions = 1; chondrule sizes range from 50 µm to >1 mm; chondrule type modes (vol. %) are porphyritic olivine = 21, porphyritic olivine-pyroxene = 4, cryptocrystalline = 3, granular olivine = 3, other = 1; matrix is mostly uncrystallized; fine grained olivine, Fa₃₅, NiO = 0.25 wt. %; plagioclase, An₈₀; Ca-rich pyroxene Wo₄₆Fs₉; Ca-poor pyroxene Fs_19.6; contains Ni-rich sulfides and Cr-rich magnetite (Cr₂O₃ = up to 13.9 wt. %); weathering grade, W0/1. Specimens: 13.8 g plus thin section, NAU; main mass with finder.

NWA 772. Image © T. E. Bunch, 2004

Northwest Africa 1112

Morocco
2001
Carbonaceous chondrite (CK5)

A 49 g complete stone was purchased in Erfoud, Morocco October 2001. Classification and mineralogy (T. Bunch and J. Wittke, NAU): well equilibrated, abundant matrix (~75 vol. %). Matrix olivine, Fa_30.1 (range Fa_29.9-30.3); (O.46 wt. % NiO); plagioclase, An_31.8Or_4.1 (range An_28.3-38); green diopside, Fs_1.5Wo_45.2En_45.2. Magnetite Cr₂O₃ and Al₂O₃ contents are lower in abundance than in less equilibrated CKs, 3.87 wt. % and 0.29 wt. %, respectively, with TiO₂, 0.27 %; MnO 0.18 %; NiO, 0.31 % and CoO, 0.14 %. Phosphate and Ni-, Co-rich pyrrhotite. Very fresh. Shock level, S2. Specimens: type specimen, 9.1 g, NAU; main mass, Hupé.

Northwest Africa 1284

Morocco
2001
Carbonaceous chondrite (CK4/5)

A 56 g stone was purchased in Erfoud in October 2001. Classification and mineralogy (J. Wittke and T. Bunch, NAU): mostly recrystallized olivine-rich matrix with poorly crystallized plagioclase (mottled extinction, low birefringence, and up to 0.12 wt. % NiO). Matrix olivine, Fa_31.5 (range, Fa_31.1-32.0) (0.45 wt. % NiO); plagioclase, An_51.8Or₅ (range An_44.5-63.1); magnetite, 4.6 wt. % Cr₂O₃; 1.62 % Al₂O₃; 0.31 % NiO; 0.37 % TiO₂; 0.25 % CoO and 0.17 % MnO. Contains minor pentlandite, pyrrhotite, and phosphate. Low degree of weathering and shock level, S2. Specimens: 11.3 g, NAU; main mass, Hupe.

Northwest Africa 1628

Northwest Africa
Found 2003
Carbonaceous chondrite (CK5)

A 35.7 g stone was purchased in Rissani, Morocco in September 2003. Description and classification (T. Bunch and J. Wittke, NAU): Partially shock-melted/crystallized CK (S3-6) of undeterminable petrologic grade. Cataclastic matrix consists of massive olivine (Fa₃₁) with many microns-size magnetite inclusions (Cr₂O₃ = 0.57 wt. %; Al₂O₃ = 3.1 wt. %) and plagioclase (An_29.3). Several chondrules with thick, fine-grained rims, are mantled with felty masses of quench-form, alumina-rich, low-Ca pyroxene (Fs_23.2En_76.8), set in Ca-rich mesostasis. Many other chondrules also show characteristics of partial melting. Medium weathering grade. Specimens: 7.8 g, NAU; main mass, Oakes.

Northwest Africa 1694

Morocco
Found 2002
Carbonaceous chondrite (CK3)

NWA 1694. Image © T. E. Bunch, 2004

A 47.1 g stone was purchases in Safsaf, October 2002. Mineralogy and classification (T. Bunch and J. Wittke, NAU): fresh stone (shiny fusion crust with slight interior staining near the surface) with 80 % fusion crust. Modes (in vol. %): matrix, 47; chondrules, 44; sulfides, 6; Cr-magnetite, 2; refractory inclusions, 1. Chondrules range in size from 0.08 to 1.2 mm. Matrix mostly unrecrystallized, fine-grained (<5 µm) olivine, Fa₃₇; augite, Fs₁₅Wo₄₇; Ca-poor pyroxene, Fs₂₉; Ni-rich sulfides (Co up to 0.84 wt. %) and Cr-rich magnetite (Cr₂O₃ up to 16.51 wt. %). Sulfides contain many small (<20 µm), rounded inclusions of Cl-apatite and SiO₂ glass. Similar to, but not paired with NWA 772. Contains Ca,Al-rich inclusions. Shock level, S1; weathering grade, W0/1. Specimens: type specimen, 9.42 g and one thin section, NAU; main mass, Hupé.

Northwest Africa 1907

Morocco
Found 2003
Carbonaceous chondrite (CK5)

NWA 1907. © T. E. Bunch, 2004

A 476 g stone was purchased in Rissani in June 2003. Classification and mineralogy (J. Wittke and T. Bunch, NAU): coarse, recrystallized matrix and some chondrule margins. Olivine is equilibrated at Fa_32.2 (range 32.1-32.4) with NiO = 0.52 wt. %; large patches of plagioclase with variable composition between An₃₂ and An₆₀; magnetite contains 5.3 wt. % Cr₂O₃ and 1.88 wt. % Al₂O₃; troilite, and phosphate. Shock level, S2/3; weathering grade, W2. Specimens: type specimen, 22.15 g, NAU; main mass, Farmer.

Northwest Africa 2129

Northwest Africa
Found 2003
Carbonaceous chondrite (CK3/4)

A 994 complete, mostly crusted stone was purchased in Erfoud in December 2003. Description and classification (T. Bunch and J. Wittke, NAU): well-defined chondrules in a partially crystallized matrix. Matrix olivine, Fa_30.3-33.9, NiO = 0.54 wt. %; magnetite, Cr₂O₃ = 6.0-7.2 wt. %, Al₂O₃ = 1.92 wt. %, NiO = 0.41 wt. %, TiO₂ = 0.5 wt. %. Transitional assignment of CK3/4 made on the basis of heterogeneous matrix, olivine composition, and magnetite composition (> 9 wt. % Cr₂O₃ in CK3s and < 6 wt. % in CK4s). Shock level, S2 and low weathering grade. Specimens: 23.4 g, NAU; Main mass, Hupé.

Northwest Africa 2372

Northwest Africa
Found 2004
Carbonaceous chondrite (CK4)

A 440 g single, brownish stone was purchased in Erfoud, Morocco in May 2004. Description and classification (T. Bunch and J. Wittke, NAU): contains ~33 vol. % chondrules that are typically smaller than most CK meteorites (<1 mm diameter), abundant melilite-spinel CAIs rimmed by subcalcic augite, and partially rcrystallized matrix. Matrix olivine, Fa_29.5-34.2 (FeO/MnO = 30.8-37.8 g/g); low-Ca pyroxene, Fs_25.3-29.0Wo_0.9-5.3 (FeO/MnO = 25.3-29.0 g/g); plagioclase, An_36.8-51.2Or_1.7-3.0; magnetite, Cr₂O₃ = 5.3 wt. %, Al₂O₃ = 5.3 wt. %, TiO₂ = 1.97 wt. %, troilite, and Fe-, Mg-rich feldspathic glass. A portion of the glass has been replaced by terrestrial carbonate. Shock level is S2, weathering grade, W3. Specimens: type specimen, 23 g, NAU; main mass. Reed.

Northwest Africa 2386

Northwest Africa
Purchased September 2004
Carbonaceous chondrite (CK4)

A 440 g single stone with weathered crust was purchased in Erfoud, Morocco. Description and classification (J. Wittke and T. Bunch, NAU): contains ~42 vol. % small chondrules with ~13 vol. % CAI components dominated by melilite-spinel aggregates, rimmed by diopside or subcalcic augite. Chondrules have well-defined rims and mostly crystallized mesostasis. Matrix is partially recrystallized with minor Fe-, Mg-rich feldspathic glasses. Olivine is fine-grained and poorly crystallized. Matrix olivine, Fa_29.5-34.8 (FeO/MnO = 31-37 g/g); low-Ca pyroxene, Fs_25.3-29.0Wo_0.9-5.3 (FeO/MnO = 25.3-29.0 g/g); plagioclase, An_41.0-51.2Or_2.1-2.9; magnetite, Cr₂O₃ = 5.3 wt. %, Al₂O₃ = 1.86 wt. %, TiO₂ = 1.97 wt. % and NiO = 0.31 wt. %. Moderately weathered and lightly shocked (S2). Specimens: type specimen, 22 g, NAU; main mass, Reed.

Northwest Africa 2388

Northwest Africa
Purchased 2004 September
Carbonaceous chondrite (CK6)

An 81 g fresh and fully crusted stone (with primary and secondary ablation surfaces) was purchased in Erfoud, Morocco. Description and classification (T. Bunch and J. Wittke, NAU): fully equilibrated and recrystallized with a few indistinct, relict chondrules. Abundant plagioclase forms a discontinuous network around enclaves of olivine, Ca-pyroxene, and magnetite matrix and around relict chondrules. Olivine in matrix and chondrules is very homogeneous, Fa _31.9-32.6 (N = 26) and very low MnO contents (FeO/MnO = 113-137 g/g); Ca-pyroxene, Fs_20.5Wo_50.5 (FeO/MnO = 98-118 g/g); plagioclase, An_85.9Or_7.4. All silicates contain NiO: olivine, 0.62-0.82 wt. %, Ca-pyroxene, 0.78-1.09 wt. %, plagioclase, 0.41-0.49 wt. %. Magnetite, Cr₂O₃ = 5.3 wt. %, Al₂O₃ = 2.36 wt. %, NiO = 0.51 wt. %. Moderately weathered and low shock level. Specimens: type specimen, 16.2 g, NAU; main mass, Reed.

Northwest Africa 2708

Morocco
Found 2004
Carbonaceous chondrite (CK4)

History: A single partially crusted stone of 528 g was purchased in Erfoud, Morocco, in January 2005.
Petrography: (J. Wittke and T. Bunch, NAU) Specimen contains rare, partially altered CAI; melt clasts and chondrules with fairly sharp margin/matrix boundaries. Geochemistry: Matrix olivine (Fa_29.7±2.7), magnetite (Cr₂O₃ = 4.6, Al₂O₃ = 2.19 [both wt. %]), poorly crystallized plagioclase (An_78.4, pentlandite (Co = 1.87 wt%). Chondrules: Olivine (Fa_30.6±1.95), Ca-rich pyroxene (Fs_43.5Wo_48.7), magnetite (Cr₂O₃ = 3.2, Al₂O₃ = 1.0 [both wt. %]). Magnetite in melt clasts contains Ni-bearing, exsolved ilmenite.
Classification: Carbonaceous chondrite (CK4); host = low shock; clasts = moderate to highly shocked, moderate weathering.
Specimens: A 20.3 g type specimen is on deposit at NAU. G. Hupé holds the main mass.

Northwest Africa 3116

Morocco
Found 2002
Carbonaceous chondrite (CK5)

A 27 g stone was purchased in Erfoud, Morocco in 2002. Description and classification (T. Bunch and J. Wittke, NAU): contains numerous amoeboid and melilite-spinel - rich CAIs; well crystallized matrix of mostly fine-grained olivine (Fa_35.4), plagioclase (An_39.5), magnetite (Cr₂O₃ = 2.93 wt. %; Al₂O₃ = 2.85 wt. %; MgO = 0.65 wt. %; P₂O₅ = 0.35 wt. %; TiO₂ = 0.85 wt. %; NiO = 0.43 wt. %; CoO = 0.26 wt. %), and troilite. Several large xenoliths of shock-melted/crystallized material contains sheaths of Ca-rich pyroxene (Fs_14.1Wo_49.1) set in a groundmass of microns-size Ca-poor pyroxenes (Fs_34.2Wo_2.0) and pentlandite (Ni = 36.7 wt. %). Shock level, S3 (xenoliths, S6); low weathering grade. Specimens: 5.4 g, NAU; main mass, Hupé.

NWA 3116. © T. E. Bunch, 2004

Northwest Africa 4812

Northwest Africa
Find: 2006
Carbonaceous chondrite (CK)

History and physical characteristics: A 68 g stone was purchased in Erfoud, Morocco by Stefan Ralew in 2006. Patchy distribution of dark gray fusion crust and desert etching.
Petrography (T. Bunch and J. Wittke, NAU): dark interior with very dark chondrules and shock-melt clasts, the matrix is nearly opaque. Highly shocked and shock-darkened by melting to partial melting of matrix and redistribution of fine-grained magnetite similar to shock darkening of ordinary chondrites and redistribution of fine-grained metal droplets. Contains olivine, orthopyroxene, pigeonite, plagioclase, felsic glasses, Cr-magnetite, FeS, and pentlandite. The shock level is very high at S5 and the weathering grade is low.
Mineral compositions: Olivine, Fa_30.3 (FeO/MnO = 110); orthopyroxene, Fs_26.4Wo_0.7 (FeO/MnO = 74); pigeonite, Fs_21.1Wo_12.1 (FeO/MnO = 64); plagioclase, An_59.3 and magnetite, Cr₂O₃ = 3.64 wt. % and Al₂O₃ = 1.26 wt. %.
Classification: Carbonaceous chondrite (CK). High shock effects preclude further subtype classification.
Type specimen: A total of 3.9 g and one thin section are on deposit at NAU. Mr. Stefan Ralew is the main mass holder.

Other CK Carbonaceous Chondrites

Photographs of CK Chondrites

NWA 2787. © T. E. Bunch, 2005