Lunar Meteorite: Lynch 002
from The Meteoritical Bulletin, no. 100
Western Australia, Australia
Classification: Lunar meteorite
History: A weathered mass was found on an open plain during systematic meteorite searching.
Physical characteristics: The 36.54 g irregularly shaped stone lacks fusion crust and measures 4 × 4 × 2 cm. It has a dark, desert-varnished surface.
Petrography: (C. L. Smith and A. T. Kearsley, NHM) The sample is highly brecciated from the micro to macro-scale, and contains numerous clasts in a heterogeneous, brecciated matrix. Melt veins, some containing blebs of Fe-Ni metal, are pervasive. Melt spherules are also observed. Larger clasts to ~1 mm are composed of basaltic lithologies, melt clasts, KREEP-rich clasts, and pyroxferroites. The matrix is brecciated and heterogeneous and is composed of mono and polymineralic fragments. Many of the smaller polymineralic fragments appear similar to the larger clasts. Matrix consists predominantly of pyroxene and feldspar. Irregularly shaped Fe-Ni metal grains (few micrometers to few tens of micrometers) occur and sulphide and schreibersite are also observed. Ilmenite grains are fairly abundant. Accessory phases include baddeleyite and silica. The sample is moderately fractured and carbonate veins fill cracks and voids. No fusion crust remains, although there is a distinct weathering rind preserved in some places.
Geochemistry: Representative large clasts; basaltic clast pyroxene (Fs24.5-41.8Wo6.1-34.3, Fe/Mn=58.4-74.3 and Fs18.9–72.2Wo4.9-24.1, Fe/Mn=51.1-77.6), plagioclase (An86.7-93.6Or0.4-2.5 and An88.3-92.1Or0.7-2.0); pyroxferroite clast (Fs45.0-58.8Wo21.5-39.0, Fe/Mn=71.5-96.8). Matrix low-Ca pyroxene (Fs20.4-74.9Wo1.6-17.8, Fe/Mn=47.8-76.3), high-Ca pyroxene (Fs6.6-70.1Wo20.5-51.4, Fe/Mn=40.0-96.0), plagioclase (An83.4-98.8Or0.0-1.5). All analyses by EPMA.
Oxygen Isotopes: I. A. Franchi (OU) δ17O = 3.638, 3.470 δ18O = 7.005, 6.676 Δ17O = -0.005, -0.002 all values in per mil. Bulk acid washed sample.
Classification: Achondrite, lunar breccia with moderate to high weathering.
Specimens: Main mass and one polished block at WAM.
The chemical composition of Lynch 002 has been more severely altered by terrestrial weathering effects than any other lunar meteorite that I have studied.
It is compositionally distinct from Calcalong Creek, the only other lunar meteorite from Australia, but similarly rich in incompatible elements like Th. The two Australian lunar meteorites were found 859 km apart.
Meteoritical Bulletin Database
Korotev R. L. (2013) Composition of Lynch 002 lunar meteorite. 76th Annual Meeting of the Meteoritical Society, abstract no. 5021.
Pernet-Fisher J. F., Nottingham M., Curran N. M. , and Joy K. H. (2020) Cosmic-ray exposure histories of Th-rich lunar regolith breccias. 51st Lunar and Planetary Science Conference, abstract no. 1376.
Robinson K. L., Smith C. L., Kearsley A. T., Bevan A. W. R., and Anand M. (2016) The Lynch 002 lunar meteorite revisited. 46th Lunar and Planetary Science Conference, abstract no. 1470.
Smith C. L., Kearsley A. T., Bermingham K. R., Deacon G. L., Kurahashi E., Franchi I. A., and Bevan A. W. R. (2012) Lynch 002: A new lunar meteorite from the Nullarbor Desert, Western Australia. 75th Annual Meeting of the Meteoritical Society, abstract no. 5137.