1%''())+@+'A CHONDRULE MICROMETEORITE FROM ANTARCTICA WITH VAPOR FRACTIONATED TRACE ELEMENT ABUNDANCES. G.Kurat1, P.Hoppe2, and C.Engrand1, 1Naturhistorisches Museum, A-1014 Vienna, Austria; 2Physikalisches Institut, Universitt Bern, CH-3012 Bern, Switzerland. Chondrules are rare among micrometeorites (MMs) but apparently do contribute to the cosmic spherule (CS) population [e.g., 1]. This probably is caused by the relatively large masses of chondrules which prevent atmospheric entry without fusion. However, a few unmelted MMs do appear to be original chondrules. One such object was found in mount 944(#32). This chondrule was studied in detail by utilizing optical microscopy, scanning electron microscopy, electron microprobe, and ion microprobe techniques. Chondrule 94-4-32 is a ~80% fragment of an originally oval radiating olivine chondrule with about 120 m in diameter. Olivine has ~ Fa35, is platy, only a few micrometer thick but up to about 50 m long. Between the plates are variable amounts of Na, Ca, Al-rich glass and also some open pore space, a few clinopyroxenes, and sub-m grains of pentlandite. The bulk composition of 94-4-32 is principally chondritic but enriched in CaO (3.8 wt%) and depleted in NiO (0.02 wt%), K2O (<0.02 wt%), and S (SO3=0.33 wt%) as compared to chondrites. However, trace element abundances (Figure) are distinctly different from those in chondrites. All highly refractory elements (Zr, Y, Th, Sc, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) have sub-chondritic abundances (0.007-0.7xCI) whereas the moderately refractory elements (Ti, Nb, La, Ce, Pr, Nd, Eu, Be, Si and Ba) have super-chondritic abundances (~2-7xCI). The moderately volatile elements Li and Cr have about chondritic, and Co, Ni, sub-chondritic abundances. The depletion of 94-4-32 in siderophile elements and the presence of pentlandite can be taken as additional indications for that particle being a chondrule. Fractionated lithophile element abundances have been observed in chondrules from a few chondrites [e.g., 2,3] and are probably due to sampling fractionation. Chondrule 94-4-32, however, has lithophile element abundances which clearly reflect vapor fractionation. Although vapor fractionation is common in chondrules from carbonaceous chondrites [e.g., 2, 4], it is usually of a different kind with the refractory elements enriched and unfractionated and the moderately volatile elements depleted. In the case of chondrule 94-4-32 the fractionation of the lithophile elements is comparable to that found in typeII CAIs [5] and, thus, gives evidence for the formation of that chondrule by condensation from a vapor which was depleted in the super-refractory elements. A condensation origin of some chondrules, like the RP chondrules, had been shown to be likely because of vapor fractionated siderophile element abundances [6]. However, chondrule 94-4-32 is the first chondrule found so far which carries an unequivocal signal of condensation in its lithophile elements. A similar fractionation pattern of lithophile elements is also present in some cosmic spherules [1]. Chondrule 94-4-32 and these cosmic spherules indicate that such matter is apparently more abundant in the interplanetary dust, which bears compositional similarities to CM/CR chondrites [7], than in chondrites, but what does this imply? Acknowledgments: Support by the FWF in Austria and the Schweizerische Nationalfonds in Switzerland and help with EMPA by J. Walter is gratefully acknowledged. References: [1]Walter J. et al. (1995) LPSC XXVI, 1457; [2]Kurat G. (1984) Proc. 27th IGC 11, 155; [3] Kurat G. et al. (1983) EPSL 68, 43; [4]Rubin A. E. and Wasson J. T. (1987) GCA 51, 1923; [5] Martin P.M.and MasonB. (1974) Nature 149, 333; [6]Kurat G. et al. (1985) LPSC XVI, 471; [7]Kurat G. et al. (1994) GCA 58, 3879; [8]Palme H. et al. (1981) in: Landolt-Boernstein (eds.: K. Schaifers and H. H. Voigt), Springer Verlag, pp 257. Figure: Normalized [8] trace element abundances in chondrule 94-4-32 (as measured by SIMS) compared to those of two typical RP chondrules from Allende [6]. xunkdaZWP7M8F````````D`a 8x q^n_gxdy] Z W]TfQNKb`b`a``````` xurol'iIfQcs`y]ZVD`b`b`b`b`b` m`SvS S5SSF9 <h < < < < nnnnnnl= <h =/2$;(hUa>?@um}A RP CHNDRULE MICROMETEORITE FROM ANTARC04/27/9604/27/96EDV-LeitungEDV-Leitung04/25/9604/27/96