SOCORRO

Stony

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ACHONDRITE

MARTIAN

SCN

SHERGOTTITE

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BRAZIL - PE

2019

Martian Shergottite

PETROGRAPHY:

(C. Agee, UNM) The two major phases in this meteorite are clinopyroxene and maskelynite. Ubiquitous minor phases are merrillite/apatite, titanomagnetite, ilmenite and silica. The clinopyroxene has a modal abundance of approximately 60%, with significant core to rim zoning observed in backscattered electron images indicating an igneous crystallization trend with Mg-rich sub-calcic augite cores, mantled by intermediate pigeonite, and rimmed with ferropigeonite. Clinopyroxene average grain size is approximately 500-1000 μm. Maskelynite has modal abundance of approximately 30%, most grains are subophitic with maximum length ~1 mm. Merrillite laths are up to 1 mm in length. There are numerous domains of fine-grained intergrowths or quench crystals presumably formed during a shock event.

GEOCHEMISTRY:

(C. Agee, UNM) Clinopyroxene Fs57.3±21.4Wo19.5±7.5, core to rim range Fs29.0Wo30.6 (sub-calcic augite) – Fs83.5Wo11.7 (ferropigeonite), Fe/Mn=36±5, n=34; maskelynite An47.0±7.7Ab50.8±6.0Or2.2±1.8, n=11; fusion crust (20 μm defocused electron beam) SiO2=47.5±0.7, TiO2=0.96±0.04, Al2O3=11.9±0.3, MgO=4.1±0.1, FeO=18.9±0.3, MnO=0.44±0.03, CaO=9.8±0.1, Na2O=2.3±0.1 (all wt%), titanomagnetite FeO=52.8±1.2, Fe2O3=19.2±1.4, TiO2=24.2±1.1, Al2O3=1.9±0.6±0.4, (all wt%), n=3; Oxygen isotopes (K. Ziegler, UNM): 5 acid-washed fragments analyzed by laser

CLASSIFICATION:

Evolved martian basalt, clinopyroxene compositional zoning trends are similar to QUE 94201.

CLASSIFIERS:

C. Agee

HISTORY:

Physical characteristics: The remaining MNRJ sample measures 36.2 × 25.1 × 14.4 mm and weighs 24.4 g. It is an end-piece of a larger stone with a distinct angular edge and shows dark-brown fusion crust. The cut surface exhibits a slightly brownish-gray interior. Microscopically, the meteorite is quite fresh, with metal phase preserved.

All information that does not have a specific source was extracted from the Meteoritical Bulletin Database.

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