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MacAlpine Hills 88104
Basic information Name: MacAlpine Hills 88104
     This is an OFFICIAL meteorite name.
Abbreviation: MAC 88104
Observed fall: No
Year found: 1988
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 61.2 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 12(2)  (1989)  Lunar (anorthositic breccia)
Meteoritical Bulletin:  MB 76  (1994)  Lunar-anorthositic
NHM Catalogue:  5th Edition  (2000)  Lunar (anorth)
MetBase:  v. 7.1  (2006)  Lunar (anorth)
Recommended:  Lunar (anorth)    [explanation]

This is 1 of 69 approved meteorites classified as Lunar (anorth).   [show all]
Search for other: Lunar meteorites
Writeuphelp
Writeup from AMN 12(3):
[From AMN 12(2):]

Sample No: MAC88104, MAC88105

Weight (g): 61.2; 662.5

Dimensions (cm): 4 x 4.5 x 2.5; 11 x 7.5 x 6.5

Location: MacAlpine Hills; MacAlpine Hills

Field No.: 5757; 5759

Weathering: A/Be; A/Be

Fracturing: A/B; A/B

Meteorite Type: Anorthositic Breccia

 

Macroscopic Description: Roberta Score

MAC88104 and MAC88105 are paired fragments of a polymict breccia. Both specimens have thin gray-green fusion crust which covers approximately 30% of the exterior surface. The other exterior surfaces are dark gray and weathered, with numerous clasts and vugs where clasts have been plucked out by weathering. A minute amount of evaporite minerals is evident in the minor cracks in the fusion crust. The interior is blue gray and mostly fine-grained, but glassy in some areas. Veins of dark vesicular glass surround some clasts, but do not transect any clasts. The meteorite contains abundant angular feldspathic clasts and fine-grained gray, black and beige clasts. The largest clast exposed (1.5 x 1 cm) is fine-grained and anorthositic, with scattered mafic minerals. Other clasts are medium-grained and more mafic.

 

Thin Section (MAC88105,6) Description: Brain Mason

 

The section shows a microbreccia of small (up to 3.0 mm) mineral grains and clasts (up to 3 mm across) in a translucent to semi-opaque brown glassy matrix. The mineral grains are almost all plagioclase, except for a few olivines; one minute grain of metal or metal-sulfide was seen. Some of the clasts consist almost entirely of dark brown semi-opaque glass; others show small plagioclase laths with interstitial glass; one appears to be fine-grained troctolite. Microprobe analyses show that the plagioclase is almost pure anorthite (Na2O 0.3 - 0.5%, K2O less than 0.1%). Olivine composition is Fa10-18; its FeO/MnO ratio is very high, 60 - 80, characteristic of lunar material. The average composition of the glassy matrix is (weight percent): SiO2 45, Al2O3 28, FeO 6.3, MgO 4.7, CaO 16, Na2O 0.36, TiO2 0.32, MnO 0.11, K2O <0.1, i.e. anorthositic. The meteorite is an anorthositic microbreccia, almost certainly of lunar origin.


[From AMN 12(3):]

AMENDED VERSION

Sample No.: MAC88104; 88105

Dimensions (cm): 4x4.5x2.5; 11x7.5x6.5

Weight (g): 61.2; 662.5

Location: MacAlpine Hills

Meteorite Type: Anorthositic Breccia

Field Number: 5757; 5759

 

Macroscopic Description: Roberta Score

MAC88104 and MAC88105 are paired fragments of a polymict breccia. Both specimens have thin gray-green fusion crust which covers approximately 30% of the exterior surface. The other exterior surfaces are dark gray and weathered, with numerous clasts and vugs where clasts have been plucked out by weathering. A minute amount of evaporite minerals is evident in the minor cracks in the fusion crust. The interior is blue gray and mostly fine-grained, but glassy in some areas. Veins of dark vesicular glass surround some clasts, but do not transect any clasts. The meteorite contains abundant angular feldspathic clasts and fine-grained gray, black and beige clasts. The largest clast exposed (1.5 x 1 cm) is fine-grained and anorthositic, with scattered mafic minerals. Other clasts are medium-grained and more mafic.

 

Thin Section (MAC88104,7; 88105,6) Description: Brian Mason

The sections show a microbreccia of small (up to 0.3 mm) mineral grains, and clasts (up to 3 mm across), in a translucent to semi-opaque brown glassy matrix. The mineral grains are almost all plagioclase, except for a few olivines and pyroxenes; two pink spinel grains and one minute grain of metal or metal-sulfide were seen in 88105,6. Some of the clasts consist almost entirely of dark-brown semi-opaque glass; others show small plagioclase laths with interstitial glass; some are plagioclase-rich with minor olivine or pyroxene. Microprobe analyses show that the plagioclase is almost pure anorthite (Na2O 0.3-0.5%, K2O less than 0.1%). Olivine composition is variable, Fa10-34; most of the pyroxene is Ca-poor, averaging Wo6Fs25, but some more Ca-rich grains were analysed; the FeO/MnO ratio is very high, 50-80, characteristic of lunar material. The composition of the glassy matrix is somewhat variable, but averages (weight percent): SiO2, 45, Al2O3 28, FeO 6.3, MgO 4.7, CaO 16, Na2O 0.36, TiO2 0.32, MnO 0.11, K2O less than 0.1. The meteorite is an anorthositic microbreccia, almost certainly of lunar origin.

 

Oxygen Isotopic Composition: Robert Clayton

The oxygen isotopic composition of MAC88105 is δ18O = 5.5, δ17O = 2.7, which falls within the group of previously analyzed lunar meteorites and Apollo lunar rocks.

 

Thermoluminescence Data: Derek Sears

The measured natural TL values for MAC88104 and MAC88105 are 2.4 +/- 0.3 and 2.9 +/- 0.3 krad at 250 degrees C, respectively. This compares with Steve Sutton's values of 0.75, 1.7, and 0.5 krad for ALHA81005, YAMATO-791197, and YAMATO-82192, respectively, and with typical values for most Antarctic chondrites of 20-80 krad. These low values reflect recent heating or anomalous (non-classical) fading, observed for some lunar meteorites. (Sutton, 1985, Proc. 10th Symp. Antarctic Meteorites, 133-139: 1986, Meteoritics, 21, 520-521: 1989, personal communications).

 

26Al Measurement: John Wacker

26 Al activity of MAC88105 is 19.5 ± 2.6 dpm/kg which is considerably lower than the 41-139 dpm/kg measured by Nishiizumi et al. (1988; Meteoritics 23, 294-295) in four other lunar meteorites. The low activity implies either an unreasonably old terrestrial age (>1 MY) or that the sample was heavily shielded on the moon and had a short transit time in space.

Data from:
  MB76
  Table 2
  Line 4652:
Mass (g):61.2
Class:Lun-A
Weathering grade:A/Be
Fayalite (mol%):24
Ferrosilite (mol%):19-28
Plots: O isotopes:  
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References: Published in Antarctic Meteorite Newsletter 12(3) (1989), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (84° 13'S, 160° 30'E)
     Recommended::   (84° 13'S, 160° 30'E)

Statistics:
     This is 1 of 33933 approved meteorites from Antarctica (plus 6798 unapproved names)
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