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Acapulcoites

NWA8287

Name

*click on the Name for more information

Structure Class

Primitive achondrites

Chemical Class

Acapulcoite

Country

(Northwest Africa)

Year found

2013

Mass

221 g

[Museum Collection]

(1)1.35g   (2)1.28g   (3)1.23g   (4)1.18g

(5)1.13g   (6)1.11g   (7)1.09g   (8)1.06g

(9)1.02g   (10)1.02g   (11)0.99g   (12)0.89g

(13)0.86g   (14)0.83g   (15)0.80g   (16)0.77g

(17)0.73g   (18)0.66g

History: Purchased by Brahim Tahiri from a Moroccan meteorite hunter and sent to his partner Sean Tutorow for classification, 2013. Physical characteristics: Single stone, weathered exterior with dark brown patina. Saw cut reveals abundant metal and sulfide set in a fine-grained silicate groundmass. Petrography: (C. Agee, UNM) Microprobe examination of a polished mount. Silicates: ~95% orthopyroxene, ~3% plagioclase, ~2% diopside. Silicate grains 50-200 μm, polygonal texture with 120° triple-junction grain boundaries. Numerous kamacite and troilite domains up to 1000 μm which constitute ~25% of this meteorite. Metal/sulfide veinlets throughout, many on grain boundaries. Geochemistry: (C. Agee and H. Miley, UNM) Orthopyroxene Fs10.6±0.1Wo1.7±0.3, Fe/Mn=14±1, n=7; diopside Fs4.9±0.1Wo44.0±0.3, Fe/Mn=10±1, Cr2O3=1.06±0.02 wt%, n=6; plagioclase Ab73.5±0.7An23.6±0.6Or2.9±0.2, n=8; kamacite Ni=10.8 wt%. Oxygen isotopes (K. Ziegler, UNM) Oxygen isotope values of 4 acid-washed aliquots of bulk sample, 1.5, 1.2, 1.5, 1.0 mg, gave δ17O = 0.121, 0.236, 0.356, 0.500, δ18O = 2.330, 2.585, 2.944, 3.200, Δ17O = -1.109, -1.129, -1.198, -1.190 (linearized, all permil). Classification: Primitive achondrite (Acapulcoite) based on oxygen isotopes which are coincident with the acapulcoite/lodranite field, distinguished from lodranite type by the modal abundance of plagioclase and the relatively small silicate grain size. This acapulcoite is a highly equilibrated orthopyroxenite and is unique in that olivine is absent. Specimens: 20.03 g including a probe mount on deposit at UNM, Sean Tutorow holds the main mass.

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