Data Al

**th Annual Meteoritical Society Meeting (****) **38.pdf

DISCRIMINATION OF ACAPULCOITES AND

LODRANITES FROM WINONAITES. D. Rumble, III1,

A. J. Irving2, T. E. Bunch3, J. H. Wittke3 and S. M. Kuehner2,

1

Geophysical Laboratory, Washington, DC 20015

abpcjv@r.postjobfree.com; 2Earth & Space Sciences, Univ. of

Washington, Seattle, WA 98195; 3Dept. of Geology,

Northern Arizona University, Flagstaff, AZ 86011.

Introduction: Combined petrological and oxygen

isotopic analyses of five Northwest African primitive

achondrites (NWA 516, NWA 1457, NWA 1617, NWA

2627 and NWA 2656) have clarified the relationships among

acapulcoites, lodranites and winonaites. It would not be

possible to properly classify some specimens in these groups

using their mineral compositions alone (see plot below).

Petrology: These new specimens have polygonal-

granular textures (grainsize 0.4-0.8 mm) and lack chondrules.

Mineral compositions are, respectively: orthopyroxene Fs

1.25, 6.2, 11.2, 12.3, 8.4; olivine Fa 1.03, 5.2, 11.6, 13.1, 8.0;

plagioclase An 9.5, 14, 16, 20.9, 22, with metal, troilite and

schreibersite. NWA 516, 1457 and 2656 contain Cr-diopside

(Fs0.76Wo45, Fs2.8Wo44, Fs3.8Wo44, respectively); NWA 1457,

1617 and 2656 contain chromite (Cr/(Cr+Al) = 0.87, 0.89,

0.85, respectively); NWA 1457 contains minor Cl-apatite and

thin daubreelite blades in troilite.

NWA 1463 is a Type 5 metal-rich chondrite with a

recrystallized matrix proposed by [1] to be related to the

winonaite parent body. A sample provided to us by D.

Gregory contains Fa5.9 olivine (more ferroan than reported by

[1]), and has, respectively, 18O = 2.92, 3.18, 3.44; 17O =

1.10, 1.24, 1.40; 17O = -0.45, -0.44, -0.42 per mil.

0

Winonaites

WIN 1457 Lodranites

MM 1463

-0.4 Acapulcoites

1058

P 516

O, per mil

MD 1617 2627

-0.8 1500

17

Y74063

2656

-1.2

LOD/ACAP P = Pontlyfni

MM = Mount Morris (WI)

MD = Monument Draw

1052 2235

-1.6

0 *-**-**-**-**-**

Fa, mole%

Olivine and oxygen isotopic compositions for primitive

achondrites and related chondrites (circles). Numbers refer

to NWA specimens. Data from this work and [2].

References: [1] Benedix G. et al. 2003 66th Met. Soc.

Mtg., #5125 [2] Benedix G. et al. 1998 GCA, 62, 2535-2553;

Clayton R. and Mayeda T. 1996 GCA, 60, 1999-2018;

yamato.nipr.ac.jp/AMRC/AMRC/meteoritelist.pdf;

Bartoschewitz R. et al. 2003 66th Met. Soc. Mtg., #5114;

Mittlefehldt D. and Hudon P. 2004 67th Met. Soc. Mtg.,

#5086; Russell S. et al. 2004 Met. Bull. 88; Moggi-Cecchi V.

et al. 2005 LPS XXXVI, #1808.

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