Antarctic Meteorite Newsletter 29,1 - Petrographic Descriptions

Petrographic Descriptions Go to Pet. Desc. Page 2 of 2

Sample No.: DOM 03181

Location: Dominion Range

Field No.: 14349

Dimensions (cm): 18.0x15.5x13.0

Weight (g): 5363.9

Meteorite Type: L3 Chondrite

Macroscopic Description: Cecilia Satterwhite
The exterior of this ordinary chondrite has black fusion crust on some surfaces. Areas without fusion crust are brown and gray with a coarse grained texture. Abundant light colored inclusions are present. The interior is gray with some oxidation and rusty areas. Light colored mm sized inclusions are visible.

Thin Section (,2) Description: Tim McCoy and Linda Welzenbach

Cross-Polarized Light	Plane-Polarized Light

The section exhibits numerous well-defined chondrules (up to 1.5 mm) in a black matrix of fine-grained silicates, metal and troilite. Polysynthetically twinned pyroxene is extremely abundant and glass is preserved in a few chondrules. Silicates are unequilibrated; olivines range from Fa_1-37 and pyroxenes from Fs_1-5. The meteorite is an L3 chondrite and may be of moderately low subtype (estimated subtype 3.5).

Sample No.:	GRO 03015; GRO 03061
Location:	Grosvenor Mountains
Field No.:	15636; 15606
Dimensions (cm):	10.0x5.5x5.0 7.5x5.5x5.0
Weight (g):	480.0; 455.0
Meteorite Type:	L3 Chondrite

Macroscopic Description: Kathleen McBride
The exteriors of these ordinary chondrites have dull, black weathered fusion crust with polygonal fractures. The interiors are a dark matrix stained with rust. Numerous chondrules and a few irregularly shaped clasts are visible. Metal is also present.

Thin Section (,2) Description: Tim McCoy and Linda Welzenbach
The meteorites are so similar that a single description suffices. The sections exhibit numerous well-defined chondrules (up to 1.5 mm) in a black matrix of fine-grained silicates, metal and troilite. Polysynthetically twinned pyroxene is abundant. Silicates are unequilibrated; olivines range from Fa_1-29 and pyroxenes from Fs_3-29. The meteorites are L3 chondrites (estimated subtype 3.6).

Plane-Polarized Light	Cross-Polarized Light	Plane-Polarized Light

Sample No.:	LAP 03788
Location:	LaPaz Ice Field
Field No.:	16282
Dimensions (cm):	4.0x4.0x2.25
Weight (g):	8.255
Meteorite Type:	L Chondrite (Impact Melt)

Macroscopic Description: Kathleen McBride
60% of the exterior of this meteorite has dull black fusion crust with polygonal fractures. The interior is a gray matrix with light gray chondrules and dark gray angular inclusions. Evaporite deposits are seen near the fusion crust. Some rust is present.

Thin Section (,2) Description: Tim McCoy and Linda Welzenbach
The meteorite exhibits a relatively coarse (50-100 micron grain size), equigranular silicate matrix including rounded to irregular, sulfide-free metal blebs reaching 0.5 mm and vesicles reaching 0.5 mm. Mafic silicate compositions (Fa₂₃ , Fs₁₉ ) indicate L chondrite parentage and texture suggests it is an impact melt.

Cross-Polarized Light	Plane-Polarized Light	Cross-Polarized Light	Plane-Polarized Light

Sample No.:	LAP 03834
Location:	LaPaz Ice Field
Field No.:	16780
Dimensions (cm):	1.8x1.5x1.5
Weight (g):	5.838
Meteorite Type:	CK3 Chondrite

Macroscopic Description: Cecilia Satterwhite
80% of the exterior of this meteorite has black fractured fusion crust. The interior is a fine grained gray matrix with some oxidation. Light gray and white mm sized inclusions are visible.

Thin Section (,2) Description: Tim McCoy

Cross-Polarized Light	Plane-Polarized Light

The section consists of well-defined (up to 1 mm) chondrules in a matrix of finer-grained silicates, sulfides and very abundant magnetite. The meteorite is little weathered, but extensively shock blackened. Olivine is Fa_4-42, with most grains Fa_30-40, and orthopyroxene is Fs_11-20. The meteorite is a CK3 chondrite.

Sample No.:	LAP 03865
Location:	LaPaz Ice Field
Field No.:	16504
Dimensions (cm):	4.0x3.0x1.5
Weight (g):	19.161
Meteorite Type:	CM2 Chondrite

Macroscopic Description: Kathleen McBride
20% of the exterior has thick, polygonal fractured purple fusion crust. The interior of this carbonaceous chondrite has a black, charcoal-like matrix with an oxidation rind. Tiny white inclusions are present.

Thin Section (,2) Description: Tim McCoy and Valerie Reynolds
The sections consist of a few small chondrules (up to 0.5 mm), mineral grains and CAIs set in a black matrix; rare metal and sulfide grains are present. Olivine compositions are Fa_0-54, with a peak at Fa_0-2. The matrix consists dominantly of an Fe-rich serpentine. The meteorite is a CM2 chondrite.

Cross-Polarized Light Plane-Polarized Light Cross-Polarized Light Plane-Polarized Light

Sample No.:	LAP 03922
Location:	LaPaz Ice Field
Field No.:	16471
Dimensions (cm):	3.0x2.0x1.5
Weight (g):	15.997
Meteorite Type:	H Chondrite (Impact Melt)

Macroscopic Description: Kathleen McBride
Black fusion crust covers 40% of this meteorite's exterior. The interior is rusty with high metal content.

Thin Section (,2) Description: Tim McCoy and Valerie Reynolds

Plane-Polarized Light	Reflected Light

The section consists of highly-shocked clasts of H chondrite (Fa₁₉, Fs₁₇) material in a shock-melted matrix of relict crystals set in a fine-grained igneous matrix with metal-sulfide blebs.

Sample No.:	LAP 03923
Location:	LaPaz Ice Field
Field No.:	16455
Dimensions (cm):	3.0x2.5x1.5
Weight (g):	20.6
Meteorite Type:	CK5 Chondrite

Macroscopic Description: Kathleen McBride
The exterior is covered with brown/black fusion crust with polygonal fractures. The gray matrix has minor rust and high metal content. A few gray chondrules are visible.

Thin Section (,2) Description: Tim McCoy
The section consists of large (up to 1.5 mm) poorly-defined chondrules in a matrix of finer-grained silicates, sulfides and magnetite. The meteorite is little weathered, but extensively shock blackened. Silicates are homogeneous. Olivine is Fa₃₁ and orthopyroxene is Fs₂₅. The meteorite is a CK5 chondrite.

Cross-Polarized Light	Plane-Polarized Light	Cross-Polarized Light	Plane-Polarized Light

Sample No.:	LAP 03930
Location:	LaPaz Ice Field
Field No.:	16474
Dimensions (cm):	2.0x1.9x1.0
Weight (g):	8.775
Meteorite Type:	EL3 Chondrite

Macroscopic Description: Cecilia Satterwhite
95% of the exterior has brown/black fusion crust with oxidation halos. The interior is rusty with metal and some dark gray to black areas visible. Weathered mm sized inclusions are visible.

Thin Section (,2) Description: Tim McCoy and Valerie Reynolds

Cross-Polarized Light	Plane-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 small amounts of olivine. Weathering is modest, with staining of some enstatite grains and minor alteration of metal and sulfides. Microprobe analyses show pyroxene is Fs_0-17, with most grains Fs_0-2. Metal contains ~0.6 wt.% Si. The meteorite is a type 3 enstatite chondrite, probably an EL3.

Sample No.:	LAP 031097
Location:	LaPaz Ice Field
Field No.:	16432
Dimensions (cm):	1.25x1.0x0.75
Weight (g):	2.058
Meteorite Type:	H3 Chondrite

Macroscopic Description: Kathleen McBride
50% of this ordinary chondrite's exterior has brown/black fusion crust with oxidation halos. The interior has a black matrix with rust and mm sized gray chondrules.

Thin Section (,2) Description: Tim McCoy and Linda Welzenbach

Cross-Polarized Light	Plane-Polarized Light

The section exhibits numerous well-defined chondrules (up to 1.5 mm) in a black matrix of fine-grained silicates, metal and troilite. Weak shock effects are present. Polysynthetically twinned pyroxene is extremely abundant. Silicates are unequilibrated; olivines range from Fa_6-37, with most grains Fa₁₈, and pyroxenes from Fs_8-22. The meteorite is an H3 chondrite (estimated subtype 3.8).

Sample No.:	LAP 031135; LAP 031156
Location:	LaPaz Ice Field
Field No.:	16617; 16357
Dimensions (cm):	1.75x1.0x0.75 2.5x2.5x1.5
Weight (g):	2.727; 14.651
Meteorite Type:	R Chondrite

Macroscopic Description: Kathleen McBride
Exteriors are covered with fractured black fusion crust. The interiors consist of fine grained gray matrix with dark gray inclusions.

Thin Section (,2) Description: Tim McCoy and Linda Welzenbach
The sections are so similar that single description suffices. The sections consist of ~50% of well-defined, small (up to 1 mm) chondrules set in a slightly recrystallized matrix of silicates and sulfides (both troilite and pentlandite). Olivine is homogeneous (Fa_39-40) and pyroxene exhibits a small range (Fs_21-31). The meteorites are R chondrites, probably of petrologic type 4.

Cross-Polarized Light Plane-Polarized Light Cross-Polarized Light Plane-Polarized Light

Cross-Polarized Light Plane-Polarized Light

Sample No.:	LAP 031158
Location:	LaPaz Ice Field
Field No.:	16353
Dimensions (cm):	2.0x1.0x1.0
Weight (g):	4.413
Meteorite Type:	CK5 Chondrite

Macroscopic Description: Kathleen McBride
95% of the exterior has black fusion crust with polygonal fractures. The interior is a charcoal gray matrix with gray chondrules.

Thin Section (,2) Description: Tim McCoy and Linda Welzenbach
The section consists of a few large (up to 2 mm) chondrules in a recrystallized matrix of finer-grained silicates, sulfides and magnetite. Shock effects are extensive. Olivine is homogeneous at Fa₂₇. The meteorite is a CK5 chondrite.

Cross-Polarized Light	Plane-Polarized Light	Cross-Polarized Light	Plane-Polarized Light

Go to Pet. Desc. Page 2 of 2

Sample No.:	DOM 03181
Location:	Dominion Range
Field No.:	14349
Dimensions (cm):	18.0x15.5x13.0
Weight (g):	5363.9
Meteorite Type:	L3 Chondrite