Other
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27r.221f&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 221
Other
2
Scientific paper
Between December 1990 and January 1991 a field team of four, supported by the Italian Progetto Antartide from its Terra Nova base, recovered 243 samples. At time of writing, 74 stony meteorites have been classified and 6 samples have been found to be terrestrial rocks. Workers involved in classification were: R. Hutchison and M. M. Grady (Natural History Museum, London), S. J. B. Reed (Cambridge University), P. A. Bland (The Open University), C. M. Levy (University of Paris), G. Kurat (Natural History Museum, Vienna), L. Folco (University of Siena), A. Maras and M. Serracino (University of Rome), G. R. Levi-Donati (Inst. Tec. Ind. di Stato "A. Volta"), A. M. Fioretti, G.-M. Molin, and G. Salvioulo (University of Padova). Of 74 meteorites characterised, 71 are ordinary chondrites, 2 are ureilites, and 1 is an acapulcoite. Six of the ordinary chondrites are unequilibrated type 3 (3 H group and 3 L or LL group) and 8 are highly metamorphosed L7 chondrites; pairing has not yet been established. A full list of meteorite classifications will appear regularly in the Meteoritical Bulletin. The first samples can be found in The Meteoritical Bulletin, No. 72, Meteoritics 27, 109-117. Ureilites: Two stones were recovered weighing 34.6 g and 17.5 g. They are texturally and compositionally distinct and therefore represent two falls. FRO 90036 has olivine crystals varying in composition between Fa(sub)20 cores and Fa(sub)10 rims, which are mosaiced. It corresponds to type "II" after Vdovykin (1970). Average pyroxene composition is Fs(sub)16Wo(sub)3. FRO 90054 has homogeneous olivine of Fa(sub)13.1. Average low-Ca pyroxene composition is Fs(sub)16Wo(sub)5 but Ca-rich pyroxene (augite) constitutes ca. 60% of this sample. Olivine is found as discrete crystals without evidence of subgrain formation, hence type "I" after Vdovykin (1970). Acapulcoite: FRO 90011 is a 1.8-g stone. Average olivine composition is Fa(sub)9.4 and pyroxene is Fs(sub)12.6, i.e., similar to Acapulco (Palme et al., 1981) and ALHA 77081 (Mason, 1978). Silicates appear homogeneous. In a 9-mm^2 PTS this meteorite shows an achondritic coarse granoblastic texture but approximate chondrite composition, composed primarily of olivine, low-Ca pyroxene, plagioclase, troilite, and metal. Feldspar is oligoclase: Ab(sub)82.4Or(sub)5.3An(sub)12.3 and so is not dissimilar to that found in enstatite chondrites (Keil, 1968). L7 Ordinary Chondrites: FRO 90008 (1.62 g), FRO 90009 (4.88 g), FRO 90020 (0.84 g), FRO 90034 (6.39 g), FRO 90058 (27.97 g), FRO 90062 (6.23 g), FRO 90065 (5.68 g), and FRO 90066 (8.86 g) all show a highly recrystallized matrix in PTS and little or no evidence of chondrules. Most show maskelynite, implying high shock facies (Dodd and Jarosewich, 1979), but FRO 90034 has crystalline plagioclase. Textures in PTS vary slightly between specimens but it is not possible at this time to determine if some or all of these stones are paired. Silicate composition varies between an olivine composition in FRO 90008 of Fa(sub)26.6 to Fa(sub)24.6 in FRO 90058. Pyroxene composition varies between Fs(sub)23.6 in FRO 90008 to Fs(sub)19.8 in FRO 90058. PTSs of 35 samples have been issued to various groups involved in classifying the material. Another 38 PTSs are in preparation. Additional data will be available in time for the conference. Acknowledgment: EUROMET is supported by the EC through its SCIENCE (Twinning and operations) programme; contract no.: SCI* - CT91- 0618(SSMA). References: Dodd R. T. and Jarosewich E. (1979) Earth Planet Sci. Lett. 44, 335-340. Keil K (1968) J. Geophys. Res. 73, 6945-6976. Mason B. (1978) Antarctic Meteorite Newsl. 1, 19. Palme H., Schultz L., Spettel B., Weber H. W. and Wanke H. (1981) Geochim. Cosmochim Acta. 45, 727-752. Vdovykin G. P. (1970) Space Sci. Rev. 10, 483-510.
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