Northwest Africa 14807 (NWA 14807)

Morocco

Purchased: 2019

Classification: Mesosiderite (group A3)

History: The meteorite was purchased from Blaine Reed in 2019, who previously purchased it from a Moroccan meteorite dealer. Meteorite catalogued at UWO as UWO 0247.

Physical characteristics: An irregular individual with dark brown fusion crust and lighter brown broken surfaces where weathered away. The main mass longest dimension is 3 cm. Subsampled fragments are those of a somewhat weathered breccia containing metallic grains.

Petrography: Cut faces (4 cm2) reveal an interior containing many irregular elongate metallic grains, with embayed contacts on a silicate matrix. Polished thin section shows a silicate matrix of pitted pyroxene grains typically larger than 100 µm, along with clear olivine grains as irregular clasts with fine grained rims. Low-Ca pyroxene exhibits exsolution of clinopyroxene in two orientations. Pyroxene and olivine grains show sharp to undulatory extinction. Matrix is strongly recrystallized. Poilkiloblastic textures and intergrowth of plagioclase are present throughout the thin section. The total estimated mineral abundances (vol% with XRF mapping) are: 30% metal (kamacite-taenite), 40% low-Ca pyroxene, 15% plagioclase feldspar (anorthite), 5% Cr-rich olivine as clasts, 5% troilite, 5% other accessory minerals as Fe oxide weathering products, silica polymorph, clinopyroxene exsolution, schreibersite, chromite, ilmenite. BSE images show sulfide grains typically in close association with metal, but also as large (mm), spongy aggregates. Fe oxides typically surround and replace metal and pervasively fill cracks. A 50 µm melt vein composed chiefly of of Mg, Si, Ca, O glass contains spheroidal nodules of metallic Fe-Ni ranging in diameter from less than 1 µm to 10 µm.

Geochemistry: EPMA: Low-Ca pyroxene Fs_36.6±2.1Wo_3.1±0.5; FeO/MnO=25.8 (n=8); High-Ca pyroxene Fs_17.4±0.4Wo_40.8±0.5 (n=3), anorthite An_90±1 (n=6). The low-Ca pyroxene average chemical composition is Fe0.36Mg0.59Mn0.01Ca0.03Si0.98Al0.01O3. A silicate melt vein identified in BSE imaging contains spheroidal nodules of metallic Fe-Ni that also contain P and S of average composition 79.07 wt% Fe, 14.76 wt% Ni, 2.09 wt% S, 1.75 wt% P, 0.72 wt% Co (n=5).

Classification: Mesosiderite-AA. Specimen is highly recrystallized, contains abundant low-Ca pyroxene, with minor clinopyroxene exsolution. Notable abundance of plagioclase and silica polymorph consistent with group A. The presence of a silicate melt vein with metallic spherules implies textural class A3.

Specimens: One polished thin section, one polished section in epoxy, and an assortment of smaller masses (7 fragments totaling 6.13 g, and a bag of smaller pieces totaling 0.22 g) constitute 7.3 g type specimen at UWO. The 27.6 g main mass location is with Simon deBoer.