Northwest Africa 11047 (NWA 11047)

Northwest Africa

Purchased: 2015

Classification: Ureilite

History. On 2015, meteorite specimens were purchased by José Antonio Sanchez Santana in the Saharawi refugee camps in Tindouf, Algeria.

Physical characteristics. Rounded reddish-brown single stone with a mass of 51 g with black fusion crust covering 15% of the stone was found in the desert. A saw cut reveals dark polycrystalline texture.

Petrography: Petrographic description (R. P. Lozano, IGME). Polished section shows typical ureilitic equigranular texture with interlocked euhedral to subhedral olivine and pigeonite grains, 0.5 to 2 mm in size and abundant 120° triple junctions. Grain boundaries are marked by a concentration of carbonaceous material and trace amounts of troilite, nickel-iron (partly altered to terrestrial oxides), Ca-rich pyroxene and schreibersite. Olivines surrounded by reduction rims depleted in Fe (50 to 100 μm in thickness).

Geochemistry: Mineral compositions (Rafael Pablo Lozano, IGME). Microprobe analyses show pigeonite ranges from Fs_1-17Wo_1-8 with a mean of Fs_9.8±9.7Wo_6.8±1.9 and Fe/Mn=6-34 (mean Fe/Mn=13.8±11.3) (n=18). Olivine range is: Fo_77-81 (mean: Fo_78.2±2.4; n=15) with Fe/Mn=38-70 (mean Fe/Mn=50.3±5.0). Ca-rich pyroxene ranges are Fs_2-4Wo_23-37 (means: Fs_2.5±1.0Wo_33.4±5.6) and Fe/Mn=3-5 (mean: Fe/Mn=4.0±0.7) (n=5). The metal is kamacite with Ni=4.3-6.8 and Co=0.4-0.5 (all in wt.%; n=12). Troilite contains Cr (0.9-4.6), Mn (0.1-0.6) and Ni (0.1-0.5) (all in wt.%; n=9). Bulk chemistry (J. Reyes, IGME). 0.5 grams of sample for analysis. XRF of subsample gave abundances of (in wt.%): SiO₂=38.5, TiO₂<0.30, Al₂O₃=<0.60, Fe₂O₃=20.8, MgO=33.5, CaO=1.11 and K₂O<0.40. Na₂O= 0.09 wt.% by AAS. Trace elements were measured with ICP-MS (all in ppm): Be<0.1, V=83, Cr=3864, Co=113, Ni=1570, Cu=15.1, Zn=246, As=0.37, Se=2, Mo<0.5, Ag<0.1, Cd<0.5, Sb<0.1, Ba=20.2, Tl<0.1, Pb=2.77, Th=0.1 and U<0.1.

Classification (R.P. Lozano, IGME). Achondrite, ureilite. Terrestrial weathering is moderate with partial oxidation of metal.

Specimens. Type specimen (10.2 g) and a probe mount are on deposit at IGME, and 12.0 g at UCLA. José Antonio Sánchez Santana holds the main mass (Private address: C/ Río Añamaza, nº 4, Torremolinos, 29620, Málaga, Spain).