Rudraswami, N. G. ; Sahijpal, S. ; Bhandari, N. (2010) Presence of 60Fe in eucrite Piplia Kalan: a new perspective to the initial 60Fe/56Fe in the early solar system Current Science, 99 (7). pp. 948-953. ISSN 0011-3891
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Abstract
Fe-Ni isotope measurements of ferrous pyroxenes of the Piplia Kalan eucrite using Secondary Ion Mass Spectrometer revealed the presence of 60Ni excess corresponding to the initial 60Fe/56Fe of (5.2 ± 2.4) x 10-9. Combining this ratio with the inferred initial 26Al/27Al ratio of (7.5 ± 0.9) X 10~7 in plagioclase of the Piplia Kalan that has been already reported in the literature suggests initial 60Fe/56Fe of (5.2 ± 2.4) x 10-8 in the early solar system, which is significantly lower than the value inferred from Fe-Ni isotope measurements of chondrules in silicates and sulphides from unequili-brated ordinary chondrites. We attribute the difference in the initial 60Fe/56Fe to be solely due to the closure temperature of Fe-Ni isotope systematics, which is less compared to Al-Mg isotope systematics. With the initial 60Fe/56Fe values found in the Piplia Kalan, it is possible that the Fe-Ni isotope systematics was disturbed for another ~ 5 Ma (million years) after closure of the Al-Mg isotope systematics. The closure temperature of ~ 450-650°C for Fe-Ni isotope system seems feasible and we anticipate a cooling rate of ~20-60°C/Ma in the crust region of the parent body of Piplia Kalan, thereby matching the initial 60Fe/56Fe to ~ 5 X 10-7. This is consistent with the initial value found in the silicate phases in chondrules of least metamorphosed meteorites. However, the presence of 60Ni excess in Piplia Kalan does not confirm 60Fe to be a major heat source for the early thermal evolution of meteorite parent bodies. Also, it seems that a massive star probably has contributed the two short-lived nuclides, 26Al and 60Fe, to the early solar system.
Item Type: | Article |
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Source: | Copyright of this article belongs to Current Science Association. |
Keywords: | Cooling Rate; Early Solar System; Eucrite; Fe-Ni Isotope; Planetary Differentiation |
ID Code: | 88948 |
Deposited On: | 20 Jun 2012 14:01 |
Last Modified: | 19 May 2016 03:39 |
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