[meteorite-list] NWA 1839 reclassification

From: David Weir <dgweir_at_meteoritecentral.com>
Date: Sat Oct 16 09:26:53 2004
Message-ID: <41712170.83BDD6F4_at_earthlink.net>

Hello list,

I received this from Nelson to post since his computer is not
cooperating. He also mentioned that it is possibly paired with NWA 3133.

David

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Northwest Africa 1839
     Morocco
     Found 2003
     Primitive achondrite (ungrouped)
A 121.8 g, partially crusted stone was purchased in Rissani, Morocco in
June 2003. Description and classification (T. Bunch and J. Wittke, NAU):
polygonal, equigranular (<0.75 mm grain size); no relict chondrules;
prominent twinning in plagioclase. Mineral modes: orthopyroxene, 37 vol.
%; olivine, 35 vol. %; plagioclase, 12 vol. %; Ca-rich pyroxene, 6 vol.
%; troilite, 4.5 vol. %; metal (taenite only), 3.5 vol. %; chromite, 2
vol. %. Very homogeneous; silicate compositional range is within the
analytical precision of ? 0.2 mol %. Orthopyroxene, Fs18.9Wo2.3, FeO/MnO
= 41; olivine, Fa22.0, FeO/MnO = 63; plagioclase, An53.4Or2.2;
clinopyroxene, Fs7.2Wo47; taenite, Ni = 16.7 wt. %; chromite, Cr/(Cr+Al)
= 73. Oxygen isotope (D. Rumble, CIW) replicate analyses of acid-washed,
bulk sample by laser fluorination gave d18O = 0.51 and - 0.73, d??O =
-3.54 and - 4.57; D17O = - 4.18 and - 3.81 that plot near the CCAM line
and within the region of CV compositions. Shock level, S1; weathering
grade is W2. Specimens: 20.1 g, NAU; main mass, Oakes.
Received on Sat 16 Oct 2004 09:26:08 AM PDT