Ion microprobe analysis of olivine in pallasite meteorites for nickel
| Autor: | J.V.P. Long, S.J.B. Reed, Edward Scott |
|---|---|
| Rok vydání: | 1979 |
| Předmět: |
Microprobe
Olivine Thermodynamic equilibrium Analytical chemistry chemistry.chemical_element Mineralogy Pallasite engineering.material Grain size Metal Nickel Geophysics Meteorite chemistry Space and Planetary Science Geochemistry and Petrology visual_art Earth and Planetary Sciences (miscellaneous) visual_art.visual_art_medium engineering Geology |
| Zdroj: | Earth and Planetary Science Letters. 43:5-12 |
| ISSN: | 0012-821X |
| DOI: | 10.1016/0012-821x(79)90150-x |
| Popis: | The ion microprobe has been used to analyse olivine in seven pallasites for Ni. The results are in the range 22–41 μg/g and are significantly lower than published electron probe analyses. The olivine-metal equilibrium temperatures deduced from thermodynamic calculations are correspondingly lower, and it is likely that equilibrium between olivine and metal was maintained to somewhat below the temperature of the γ-α transformation in metal (∼700°C) . The results appear to be consistent with cooling rates of ∼1K/Ma derived from metal phase compositions, and certainly more so than the previous electron probe data. A Ni profile across an olivine grain in Eagle Station shows a decrease from 40 μg/g at the centre to 25 μg/g at the edge, illustrating the effect of limited diffusion of Ni in olivine during cooling. A correlation between grain size and central Ni content was also observed in Eagle Station, the smallest grains having the lowest Ni content. |
| Databáze: | OpenAIRE |
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