Antarctic Meteorite Newsletter, Volume 23, No. 2 - September 2000
Volume 23, No. 2 - September 2000

Petrographic Descriptions

Sample No.: LEW 97202
Location: Lewis Cliff
Dimensions (cm):   7.0x3.0x2.5
Weight (g): 117.596
Meteorite Type: L3 Chondrite (estimated 3.4)
    LEW97202

Macroscopic Description: Kathleen McBride
75% of the exterior of this meteorite has brown/black fusion crust with polygonal fractures and oxidation. The interior is rusty with a few light colored, mm sized chondrules. The meteorite is hard and contains numerous metal grains.

Thin Section (, 2) Description: Tim McCoy
LEW 97202 - Cross-Polarized Light The section exhibits numerous well-defined chondrules (up to 2 mm) in a black matrix of fine-grained silicates, metal and troilite. Polysynthetically twinned pyroxene is extremely abundant. Silicates are unequilibrated; olivines range from Fa1-33 and pyroxenes from Fs3-10. The meteorite is an L3 chondrite (estimated subtype 3.4).



Sample No.: LEW 97216
Location: Lewis Cliff
Dimensions (cm): 4.7x2.5x1.0
Weight (g): 22.995
Meteorite Type: L3 Chondrite (estimated 3.7)
    LEW97216

Macroscopic Description: Cecilia Satterwhite
The exterior of this meteorite has black fusion crust over 75% of its surface with oxidation haloes visible. The interior is dark gray to black with oxidation scattered and metal present.

Thin Section (, 2) Description: Tim McCoy
LEW 97216 - Cross-Polarized Light The section exhibits numerous well-defined chondrules (up to 2 mm) in a black matrix of fine-grained silicates, metal and troilite. Shock effects, including some flattening of chondrules, are evident. Polysynthetically twinned pyroxene is extremely abundant. The meteorite is weathered. Silicates are unequilibrated; olivines range from Fa9-26, with most grains Fa24-26, and pyroxenes from Fs3-4. The meteorite is an L3 chondrite (estimated subtype 3.7).



Sample No.: LEW 97221
Location: Lewis Cliff
Dimensions (cm): 4.5x4.0x2.5
Weight (g): 47.963
Meteorite Type: L3 Chondrite
    LEW97221

Macroscopic Description: Kathleen McBride
50% of the exterior of this ordinary chondrite has brown/black fusion crust with oxidation halos. The interior has a rusty matrix with light gray inclusions 1-3 mm in diameter. The meteorite is hard and coherent.

Thin Section (, 2) Description: Tim McCoy
LEW 97221 - Cross-Polarized Light The section exhibits a 7 by 10 mm clast of a highly metamorphosed ordinary chondrite in a matrix of much lower petrologic type. Mineral compositions range from Fa5-27, with most grains Fa25-26, and pyroxenes from Fs4-23. The meteorite is an L chondrite breccia with a type 6 clast in a matrix of type 3 material.



Sample No.: LEW 97225
Location: Lewis Cliff
Dimensions (cm): 1.0x0.75x1.25
Weight (g): 2.106
Meteorite Type: Ureilite
    LEW97225

Macroscopic Description: Kathleen McBride
Smooth brown/black fusion crust completely covers the exterior surface. The interior has a yellowish matrix with heavy oxidation and rust areas.

Thin Section (, 2) Description: Tim McCoy
LEW 97225 - Cross-Polarized Light The section consists of an aggregate of large olivine and pyroxene grains up to 2 mm across. Individual olivine grains are rimmed by carbon-rich material containing traces of metal. Modest shock effects (e.g., planar fractures) are present. Olivine has cores of Fa21, with rims reduced to Fa11. Most pigeonite is Fs18Wo9 with a single rim value of Fs8Wo9. The meteorite is a ureilite.



Sample No.: QUE 97657
Location: Queen Alexandra Range
Dimensions (cm): 2.0x1.5x1.5
Weight (g): 3.524
Meteorite Type: CM2 Chondrite
    QUE97657

Macroscopic Description: Kathleen McBride
This carbonaceous chondrite has a small purplish patch of fusion crust on the exterior surface. The interior has white to gray chondrules 1mm in size. The matrix is black, soft and powdery.

Thin Section (, 3) Description: Tim McCoy, Linda Welzenbach
QUE 97657 - Cross-Polarized Light This section consists of small chondrules (up to 0.8 mm), aggregates and mineral grains in a black matrix. Olivine compositions range from Fa0-49, with most Fa0-1. Low-Ca pyroxene is Fs1-5. The matrix is composed dominantly of Fe-rich serpentine. The meteorite is a CM2 chondrite.



Sample No.: QUE 97958
Location: Queen Alexandra Range
Dimensions (cm): 1.5x1.5x1.0
Weight (g): 1.754
Meteorite Type: CM2 Chondrite
    QUE97958

Macroscopic Description: Kathleen McBride
30% of the exterior of this carbonaceous chondrite has black vesicular fusion crust. The interior has a black matrix with gray crystalline inclusions up to 1 mm in size.

Thin Section (, 2) Description: Tim McCoy
QUE 97958 - Cross-Polarized Light The sections consist of a few small chondrules (up to 1 mm), mineral grains and CAIs set in a black matrix; rare metal and sulfide grains are present. Olivine compositions are Fa0-48, with many Fa0-2. The matrix consists dominantly of an Fe-rich serpentine. The meteorite is a CM2 chondrite.



Sample No.: QUE 97990
Location: Queen Alexandra Range
Dimensions (cm): 5.5x3.5x3.0
Weight (g): 67.297
Meteorite Type: CM2 Chondrite
    QUE97990

Macroscopic Description: Kathleen McBride
Exterior of this carbonaceous chondrite has rough purplish black fusion crust on 50% of the surface. Polygonal fractures and evaporites are also visible. The interior matrix is black and contains white and rust colored chondrules up to 1 mm in size.

Thin Section (, 4) Description: Tim McCoy
QUE 97990 - Cross-Polarized Light The sections consist of a few small chondrules (up to 1 mm), mineral grains and CAIs set in a black matrix; rare metal and sulfide grains are present. A slight lineation, with some chondrule flattening, is present. Olivine compositions are Fa0-61, with many Fa0-2, orthopyroxene is Fs0-1. The matrix consists dominantly of an Fe-rich serpentine. The meteorite is a CM2 chondrite.



Sample No.: QUE 97991
Location: Queen Alexandra Range
Dimensions (cm): 2.0x1.25x1.5
Weight (g): 6.766
Meteorite Type: Diogenite
    QUE97991

Macroscopic Description: Kathleen McBride
The exterior of this achondrite has dull black fusion crust on 45% of its surface. The interior is a tan matrix with melted appearing clasts and some minor cracks. The meteorite is friable and coarse grained with rust scattered. Irregularly shaped inclusions are white and black.

Thin Section (, 3) Description: Tim McCoy
QUE 97991 - Cross-Polarized Light The section shows a groundmass of coarse (up to 1.5 mm) comminuted pyroxene, with minor plagioclase and SiO2. Orthopyroxene has a composition of Fs25Wo1-4 and plagioclase is An78-85Or0-3. The Fe/Mn ratio of the pyroxene is ~30. The meteorite is a diogenite.



Sample No.: QUE 971023
Location: Queen Alexandra Range
Dimensions (cm): 3.0x1.5x1.5
Weight (g): 11.437
Meteorite Type: H3 Chondrite (estimated 3.5)
    QUE971023
 
Macroscopic Description: Kathleen McBride
This ordinary chondrite has smooth brown/black fusion crust over 90% of its exterior. Oxidation halos are visible. The interior is moldy, black and rust colored matrix.

Thin Section (, 2) Description: Tim McCoy
QUE 971023 - Cross-Polarized Light The section exhibits numerous small, well-defined chondrules (up to 1 mm) in a black matrix of fine-grained silicates, metal and troilite. Polysynthetically twinned pyroxene is extremely abundant. The meteorite is moderately weathered. Silicates are unequilibrated; olivines range from Fa6-19 and pyroxenes from Fs5-31. The meteorite is an H3 chondrite (estimated subtype 3.5).



Sample No.: KLE 98300
Location: Klein Glacier
Dimensions (cm): 3.5x2.5x2.0
Weight (g): 33.598
Meteorite Type: EH3 Chondrite
    KLE98300

Macroscopic Description: Kathleen McBride
The exterior of this meteorite has brown black fusion crust over 70% of its surface area. It has a rough texture and minor evaporates. The exposed interior has a rusty black color. The interior is a dark gray, almost metallic appearing, hard, dense material. Evaporites are present. A sulfurous odor emanates from the freshly broken faces. Circular shaped "vugs" less then 1 mm in size are visible.

Thin Section (, 4) Description: Tim McCoy, Linda Welzenbach
KLE 98300 - Cross-Polarized Light The section shows an aggregate of chondrules (up to 1 mm), chondrule fragments, and pyroxene grains in a matrix of about 30% metal and sulfide. Chondrules contain moderate to small abundances of olivine. Weathering is modest, with staining of some enstatite grains and minor alteration of metal and sulfides. Microprobe analyses show the olivine is Fa0-1 and pyroxene is Fs0-2. The meteorite is a type 3 enstatite chondrite, probably an EH3.



Sample No.: EET 99400; 99408
Location: Elephant Moraine
Dimensions (cm): 7.5x4.5x3.5;
8.0x4.5x2.0
Weight (g): 233.8; 147.736
Meteorite Type: Howardite
    EET99400 EET99408

Macroscopic Description: Kathleen McBride
Both of these achondrites have black shiny fusion crust with polygonal fractures covering 20% of the exterior. The interior is concrete gray with angular to sub angular black, white, tan and gray clasts. Olivine crystals are visible. There is no visible metal, but thin minor fractures are present.

Thin Section (, 5) Description: Tim McCoy
EET 99400 EET 99408
EET99400 EET99408
These meteorites are so similar that a single description suffices. The sections show a groundmass of comminuted pyroxene and plagioclase (up to 0.5 mm) with fine- to coarse-grained basaltic and pyroxenitic clasts ranging up to 1 mm. Pyroxene consists of orthopyroxene (Fs17-27Wo0-1), pigeonite (Fs42-50Wo13-15) and augite (Fs24Wo37). The Fe/Mn ratio of pyroxene is ~30. Plagioclase is An80-94Or0-1. The meteorites are howardites.



Sample No.: EET 99402; 99407
Location: Elephant Moraine
Dimensions (cm): 6.0x4.5x4.0;
4.5x3.0x2.0
Weight (g): 180.478; 60.043
Meteorite Type: Brachinites
    EET99402 EET99407

Macroscopic Description: Kathleen McBride
Both of these meteorites' exterior surfaces are rough, black and granular in appearance. EET99407 has some gray-black fusion crust. The interiors have a granular crystalline texture that is somewhat friable. The matrix is gray to black in color with dark gray crystalline mineral grains cemented by fine rusty material. Some areas appear like they've been melted together.

Thin Section (, 6;, 4) Description: Tim McCoy
EET 99402 EET 99407
EET99402 EET99407
These meteorites are so similar that a single description suffices. The sections are composed dominantly of equant olivine (Fa35; 0.2-1.5 mm in diameter) with 120º triple junctions. Calcic pyroxene (Fs10-12; Wo43-46) and plagioclase (An38-40; Or0.1-0.3) comprise a few percent of the meteorite each and are heterogeneously distributed. Minor chromite and iron sulfides are also present. The rocks are moderately shocked, with planar fractures in olivine and mosaicism in feldspar. The meteorites are probably brachinites.

Oxygen Isotope analysis: T.K.Mayeda and R.N.Clayton.
Our analysis for EET 99402 gives: delta-18=+3.57, delta-17=+1.65. This is indistinguishable from Brachina, for which the values are: +3.48, +1.61 (Clayton and Mayeda, 1996).


Sample No.: QUE 99001
Location: Queen Alexandra Range
Dimensions: 22 x 24 x 14.5 cm
Weight (g): 22,000
Meteorite Type: Iron, IAB (?)
    QUE99001

Macroscopic Description: Tim McCoy, Linda Welzenbach and Kathleen McBride
The mass is an irregular triangle in outline, and wedge-like in cross-section, 22 x 24 cm, and 14.5 at its widest tapering to 9.5 cm. Found partially within the ice at the time of recovery, the surface is marked by a definite line of color and texture change corresponding to the area below the ice. Almost half the meteorite, a short leg of the triangle, was below the ice. This area is light reddish-brown to orange, red and greenish oxidation colors. Luster is matte, and the surface expression is undulatory and mildly micropitted. In contrast, the above ice half is dark metallic reddish-brown, heavily sculpted and micropitted. Millimeter-sized whitish specks are evenly distributed over the same. Prominent features include a 4cm vug with minor flaking, surrounded by a whitish evaporative ring, and a 3 cm deep, 2 cm wide and 7 cm long gash-like vug, both in the below ice portion. A complete hole goes through one corner of the above ice section.

Microscopic Description: Tim McCoy and Linda Welzenbach
The main mass (,0) was cut twice. The first cut remove a 7.5 cm thick end piece cutting across the ice line and intersecting the long gash-like vug. The second cut removed a parallel 2.7 cm thick slice with a surface area of 11 x 20 cm. The cut face of the end piece and one face of the slice were polished, etched and examined in a binocular microscope for this description.

The overall structure is between a coarse (Og) and coarsest (Ogg) octahedrite with short (L/W~5) kamacite bands with bandwidths of 3-5 mm. There are coarser kamacite regions often 2-3 cm in diameter, but reaching up to 5 cm. Subgrain boundaries are common in the kamacite, as are Neumann bands. Terrestrial weathering has penetrated along many of the grain boundaries and produced cracks, even in the interior of the meteorite.

The meteorite has a prominent heat altered zone extending 1-5 mm into the interior and in some places, particularly on one side of the slice, preserves the original fusion crust.

The 7 cm long gash-like vug opens up through a small crevice into a 1.5 cm diameter tube extending back another 8-10 cm. This 1.5 cm diameter tube was filled with sulfide, which remains at the opposite end of the tube and is exposed on the opposite face of the meteorite. The large slice has an exposed troilite nodule, partially ablated during atmospheric passage, measuring 2 by 2.5 cm. The troilite is polycrystalline, with domains approaching 7 mm. Graphite is rare or absent and the troilite appears only incompletely rimmed by schreibersite. No silicates were observed.

The appearance is similar in many respects to some of the coarsest IAB irons, particularly Osseo (Buchwald, 1975). However, the troilite inclusion does not appear to contain graphite or the typical inclusion rimming sequence (graphite, cohenite, schreibersite, swathing kamacite) seen in many IAB irons. The possibility exists that this meteorite, like many Antarctic irons, is ungrouped.


Sample No.: QUE 99005
Location: Queen Alexandra Range
Dimensions (cm): 5.0x2.5x3.5
Weight (g): 64.0
Meteorite Type: Eucrite (Brecciated)
    QUE99005

Macroscopic Description: Kathleen McBride
A rough black fusion crust covers 75% of the exterior of this achondrite. The fusion crust exhibits polygonal fractures and a few shiny patches. It has a rough texture and the exposed interior is gray. The interior is fine-grained gray matrix. Near the edges are coarse black and white grains. Some black and white clasts are visible within the gray matrix.

Thin Section (, 4) Description: Tim McCoy
QUE 99005 - Cross-Polarized Light This section is dominated by fine-grained, quench-textured clasts with pyroxene microphenocrysts set in a cryptocrystalline to devitrified glassy matrix. This material is nearly identical to the unusual eucrite ALHA81001 (Warren and Jerde, 1987, GCA 51, 713-725). Coarser-grained clasts are observed bordering and intermixed with this finer-grained material. Mineral compositions are relatively homogeneous with orthopyroxene (Fs63Wo2), with fine lamellae of augite (Fs28Wo42), and plagioclase (An86-93Or0-1). The Fe/Mn ratio of the pyroxene is ~30. The meteorite is a brecciated eucrite.



Sample No.: QUE 99006
Location: Queen Alexandra Range
Dimensions (cm): 7.0x4.0x3.5
Weight (g): 133.079
Meteorite Type: Eucrite (Brecciated)
    QUE99006

Macroscopic Description: Kathleen McBride
Thin dark gray fusion crust covers 50% of this meteorite's exterior surface. Numerous vugs or plucked areas including a large one ~3 cm wide is on one surface. The interior matrix is gray and white crystalline matrix with some rusty stains. It is coarse grained, and has a soft friable texture.

Thin Section (, 5) Description: Tim McCoy
QUE 99006 - Cross-Polarized Light The section consists of a granoblastic matrix of pyroxene and plagioclase with coarser basaltic clasts up to 2.5 mm. Mineral compositions are relatively homogeneous with orthopyroxene (Fs61Wo2), with fine lamellae of augite (Fs26Wo44), and plagioclase (An86-91Or0-1). The Fe/Mn ratio of the pyroxene is ~30. The meteorite is a brecciated eucrite.