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New types of spherules from Antarctica: Meteoritic impact origin?
Author(s) -
Tazawa Yuji,
Fujii Yoshiyuki
Publication year - 1987
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl014i012p01199
Subject(s) - geology , meteorite , chondrite , snow , neutron activation analysis , ice core , geochemistry , astrobiology , debris , mineralogy , geomorphology , oceanography , chemistry , radiochemistry , physics
Spherules collected form Antarctic ice have been studied by using instrumental neutron activation analysis, energy dispersive X‐ray spectrometry and X‐ray diffration photography. Peculiar spherules, Ca‐Ti‐rich (perovskite) type (CTS) and Fe‐Cr‐Ni‐rich type (FCN), were found in the Mizuho ice core at depths of 32 to 33.5 m. Both types have rare earth element (REE) abundances; i.e., significant relative enrichment of light REE over heavy REE, which is commonly seen for terrestrial perovskite, however, with anomalous enrichment of Nd and Sm. In the Allan Hills bare ice, only a "chondritic" type without depletion of Au and S (CAS) was recognized. Size distributions and influx rates of spherules for these ices and the Mizuho surface snow indicate that Antarctic spherules are composed of steady‐falling and occasional populations. All the results combine to suggest that CTS and FCN may be droplets strewn by the impact of a huge meteorite, and CAS must be debris from one of the chondrites that fell on the source region of the Allan Hills bare ice and survive terrestrial alterations.