Computer Science
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.447b&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 447-448
Computer Science
Abundance, Breccia, Chemical Composition, Chondrites, Grain Size, Meteoritic Composition, Meteoritic Microstructures, Chemical Analysis, Geochemistry, Metallicity, Mineralogy, Volatility
Scientific paper
Kaidun is a complex breccia containing clasts at least four different lithologies. We have analyzed magnetic fractions (MKD 4-6) of three different grain sizes from the most reduced lithology of Kaidun, the Kaidun IV sample (EL3). Fractions MKD4 (fine-grained), MKD5, and MKD6 (coarse-grained) contain both isolated metal grains and metal with varying amounts of attached silicate-rich matrix. Metal grains are present as pure metal and as multiphase mineral assemblages containing variable amounts of troilite, schreibersite, graphite, enstatite, and silica. Some rounded metal nodules contain enstatite crystals of euhedral shape. The compact coarse-grained silicate-rich matrix consists mainly of enstatite. Averaged compositions of low-Ni metal and high-Ni metal are (7.2-7.7 wt% Ni, 0.32 Co, 0.34-0.38 Si, 0.15-0.18 P) and (12.2-12.6 Ni, 0.2 Co, 0.38 Si, 0.09 P) respectively. According to the analyses obtained so far, there seems to be a continuous range in metal composition. However, kamacite (6-9 wt% Ni) clusters around a mean composition with a roughly chondritic Ni/Co ratio, whereas high-Ni metal (10-16 wt% Ni) exhibits an anticorrelation between Ni and Co. The composition of schreibersite enclosed by metal is highly variable for different grains (7.5-18.0 wt% Ni, 0.10-0.28 Co) but is almost constant within grains. Samples MKD4-6 and MKD3 (nonmagnetic fraction) have been analyzed by instrument neutron activation analysis (INAA). Siderophile element abundances of the magnetic fractions normalized to CI are given. The overall abundance pattern of siderophile elements exhibits two distinctive groupings. The refractory siderophile elements show parallel fractionation trends for the different magnetic fractions with MKD6 having the lowest abundances. Molybdenum, Co, Fe, and the moderately volatile elements (Au to Sb) covary with Ni. Iron is depleted with respect to Ni and Co, whereas Au is slightly enriched, a feature typical of E chondrites.
Brandstatter Frans
Ivanov Alexei V.
Kurat Gero
Palme Herbert
Spettel Bernhard
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