|
Isotopic and trace element compositions of two
unusual Type b inclusions from the Ningqiang carbonaceous
chondrite
Lin Y., Floss C., Stadermann F. J., Zinner E. and Kimura
M. (2000) Lunar and Planetary Science XXXI, Abstract #1624,
Lunar and Planetary Institute, Houston (CD-ROM).
ABSTRACT
Two unusual Type B inclusions were found in the Ningqiang
anomalous carbonaceous chondrite. They show large variations
in melilite compositions, with åkermanite contents
decreasing from 80-90 mol% in the centers of the inclusions
to 4-15 mol% near the rims, suggesting that these inclusions
crystallized from melts. However, both inclusions also
contain fragments of fassaite, with corroded outlines and
surrounded by highly Ti-Al- enriched fringes, that may be
relict. Furthermore, one of the inclusions, NQJ331, may also
contain relict or xenolithic grains of anorthite and
palisades. The other inclusion, NQJ354, contains a
grossite-bearing spinel- hibonite spherule, which
crystallized from an SiO 2 - poor melt at high temperature
and was injected into the Type B host. Here we report Mg
isotopic and trace element measurements, undertaken in order
to clarify the complex formation and evolution of both Type
B inclusions.
|