Mathematics – Logic
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.545w&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 545-546
Mathematics
Logic
Antarctic Regions, Chemical Composition, Chondrites, Micrometeoroids, Olivine, Pyroxenes, Geochemistry, Mineralogy, Neutron Activation Analysis, Scanning Electron Microscopy
Scientific paper
In the course of a systematic investigation of micrometeorites (MM) from Antarctica we have investigated selected particles from the 100-400 microns size fraction by Instrumental Neutron Activation Analysis (INAA), Analytical Scanning Electron Microscopy (ASEM), Electron Probe Microanalysis (EMPA), and optical microscopy. Of the 60 particles analyzed so far, 36 turned out to be of extraterrestrial origin. The mineralogy and geochemistry of the unmelted MM population indicates that this most common extraterrestrial matter being sampled by the Earth is similar, but not identical, to the rare CM chondrites. One of the differences believed to be primary is the high abundance of pyroxenes in MMs and the lack of an olivine and pyroxene population very poor in Fe and rich in refractory elements. As is evident, both olivine and pyroxene compositions cluster at low Fe contents. The low Fe of both minerals is not as low in FeO as that known from CM chondrites. The MM phases are also not as rich in refractory elements, as are the most refractory olivines from CM chondrites. Their compositions are very similar exhibiting the enrichments in Mn and Cr typical of extraterrestrial olivines and pyroxenes. According to the model we can interpret the difference as indicating different intensities in processing of constituents of MMs and CM chondrites in the solar nebula. Unmelted and partially melted MMs are on average rich in low-Ca pyroxene rather than olivine as are the CM chondrites. C contents have been found to be higher in phyllosilicate MMs than in Orgueil. Thus, the MMs from the size fraction 100-400 microns, is mineralogically and chemically different from any of the known meteorite classes. It is an extraterrestrial matter of its own but seems to be related to the rare CM-type chondrites.
Brandstaetter Franz
Koeberl Christian
Kurat Gero
Maurette Michel
Presper Th.
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