Other
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27..301u&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 301
Other
1
Scientific paper
The IVA iron meteorites Steinbach (SB), Sao Joao Nepomuceno (SJN), Gibeon and Bishop Canyon are unusual in their contents of silicates. SB is particularly rich in silicates (ca. 50 wt%) and was long classified as a stony iron (Dorfler et al., 1965) but the metal fraction is typical of group IVA iron meteorites (Schaudy et al., 1972). The SB and SJN contain low-Ca pyroxene and tridymite in roughly equal proportions, whereas only tridymite is found in the two other meteorites. Reid et al. (1974) found that coexisting orthopyroxene and clinopyroxenes in SB (En 85) were formed in a narrow two-phase field at 1200 degrees C and preserved by comparatively rapid cooling. We present cooling rate estimates as well as minor element data for the silicates obtained by electron microprobe and trace elements (REE and siderophiles) for the bulk silicate fraction by INAA. The coarse granular texture of the silicates and the presence of finely dispersed sulfide inclusions in the pyroxenes might suggest a cumulate origin, but the high proportion of tridymite combined with MgO-rich pyroxene is unusual if a chondritic magma is assumed. One way of forming excess tridymite is by extreme reduction of a pallasite-type metal/olivine mixture. Our INAA data on SB bulk silicates show a pattern of REE and Sc, Cr, and Mn, which is qualitatively consistent with orthopyroxene that crystallized from a moderately evolved magma with chondritic REE levels. The incompatible elements (including Cr!) in SB pyroxene are correlated and vary up to a factor of 5 (eg., Ti and Al), whereas Ca shows a bimodal variation corresponding roughly to the coexisting orthopyroxene and clinopyroxene. The minor element variations in SB pyroxene thus resemble magmatic zoning. The SJN pyroxene is marginally more MgO-rich (En 86) and shows a similar bimodal Ca distribution although it is possibly one phase. If correct, this suggests slower cooling at a higher temperature than SB. References: Dorfler G., Hecht F. and Plockinger E. (1965) Tschermacks Min. Petr. Mitt. 10, 413-429. Schaudy R., Wasson J.T. and Buchwald V.F. (1972) Icarus 17, 174-192. Reid A.M., Williams R.J. and Takeda H. (1974) Earth Planet. Sci. Lett. 22, 67-74.
Kallemeyn Gregory W.
Rasmussen Lars K.
Ulff-Moller Finn
No associations
LandOfFree
The IVA Parent Body: Evidence from Silicate-Bearing Group IVA Iron Meteorites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The IVA Parent Body: Evidence from Silicate-Bearing Group IVA Iron Meteorites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The IVA Parent Body: Evidence from Silicate-Bearing Group IVA Iron Meteorites will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1209246