Arguin 001        20.72041, -16.07499

Dakhlet Nouadhibou, Mauritania

Purchased: 2020

Classification: Carbonaceous chondrite (CBa)

History: Reportedly found approximately 2 km west of route N2, 5 km east of the boundary of Banc d’Arguin National Park, and 40 km east of the Bay of Arguin in Mauritania. The meteorite was found by a shepherd from Mali who was grazing sheep in the area. The shepherd passed the meteorite on to a worker from a local gold field who in turn sold it to a meteorite dealer. Purchased in 2022 by Adrian Contreras from a meteorite dealer in Mauritania and subsequently sold it to Mark Lyon and Robert Ward.

Physical characteristics: Complete individual. Exterior shows numerous prominently exposed high-relief metal nodules with a golden-brown patina set in a very dark colored groundmass. Saw-cut slices reveal many densely packed bright metal nodules. Most metal nodules are in the size range 3-5 mm and are ellipsoidal in shape with the suggestion of preferred orientation or alignment. There are scattered light-colored large chondrules, some up to 1 cm in size. There is no visual evidence of macroscopic oxidation of metal.

Petrography: (A. Ross and C. Agee, UNM) This is a metal-rich meteorite dominated by well-formed kamacite-rich nodules which make up 52% by area based on SEM BSE panoramic imaging using ImageJ. Some nodules are uniform in kamacite composition while others possess interstitial sulfide between kamacite grain boundaries within a given nodule. The sulfide is a Cr-bearing troilite. Chondrules are primarily pyroxene-rich either as barred-pyroxene or cryptocrystalline pyroxene. Barred pyroxenes commonly have anorthitic "stripes" which are typically too narrow to analyze with a microprobe beam without overlap. Much of the matrix bounding the metal nodules or chondrules consists of brecciated fragments of chondrules and metal permeated by Fe-metal/oxide veinlets. Olivine occurs as smaller grains, mostly in association with pyroxene.

Geochemistry: (A. Ross, UNM) Forsterite Fa_2.9±1.0, Cr₂O₃=0.46±0.13 (wt%), n=13; enstatite Fs_3.2±1.1Wo_1.2±0.9, n=9; kamacite Fe=92.3±1.1, Ni=7.0±0.9, Co=0.35±0.05, P=0.30±0.07, Cr=0.27±0.10 (all wt%), n=10; troilite Fe=58.7±2.5, S=36.0±1.0, Cr=3.8±1.9, n=9 (all wt%). Oxygen isotopes (K. Ziegler, UNM): Three fragments analyzed by laser fluorination gave δ¹⁸O = 0.998, 1.736, 1.621; δ¹⁷O = -1.986, -1.424, -1.458; Δ¹⁷O = -2.513, -2.341, -2.314 (linearized, all per mil, TFL slope = 0.528).

Classification: Carbonaceous chondrite (CBa). This meteorite belongs to the CBa subgroup because it has large metal nodules, silicate chondrules, and magnesian olivine and pyroxene similar to other CB chondrites. Visually, polished slices of this meteorite resemble Gujba, however they are not paired as the metal nodules in this meteorite are smaller than those of Gujba and Gujba has less total metal (41 vol. %), Rubin et al. (2003). The exterior color and patina of this meteorite are distinctly different from specimens of Gujba.

Specimens: 21 g on deposit at UNM, Robert Ward holds 403.5 g of the main mass.