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Shorter 146Sm half-life and revised 146Sm-142Nd ages of planetary mantle differentiation | N. Kinoshita
; M. Paul
; Y. Kashiv
; P. Collon
; C.M. Deibel
; B. DiGiovine
; J.P. Greene
; D.J. Henderson
; C.L. Jiang
; S.T. Marley
; T. Nakanishi
; R.C. Pardo
; K.E. Rehm
; D. Robertson
; R. Scott
; C. Schmitt
; X.D. Tang
; R. Vondrasek
; A. Yokoyama
; | Date: |
22 Sep 2011 | Abstract: | The extinct short-lived nuclide 146Sm, synthesized in stellar events by the
p-process, serves as both an astrophysical and geochemical chronometer through
measurements of isotopic anomalies of its alpha-decay daughter 142Nd. Evidence
of live 146Sm, quantitatively established for the early Solar System,
constrains the time between p-process nucleosynthesis and condensation of the
first solid materials. Samarium-146 is used also to date silicate mantle
differentiation events in a number of planetary bodies, including Earth. We
performed a new measurement of the 146Sm half-life and our result, t = 68pm7
(1sigma) million year (Ma), is significantly shorter than the value currently
used for 146Sm-142Nd chronology (103pm5 Ma). We show here that the shorter
146Sm half-life value implies a higher initial Solar System ratio,
(146Sm/144Sm)_0 = 0.0094pm0.0005 (2sigma), than the recently derived value
0.0085pm0.0007, or that used in most studies 0.008pm0.001. Planetary
differentiation processes dated by 146Sm-142Nd converge to a shorter time span,
due to the combined effect of the new 146Sm half-life and (146Sm/144Sm)_0
values. The revised 142Nd age of the recently dated Lunar ferroan anorthosite
(FAN) 60025, is in agreement with its 147Sm-143Nd age; their weighted average,
196pm11 (2sigma) Ma after Solar System birth, is consistent with the
208.8pm2.4 Ma Pb-Pb age and with the age derived here (170pm15 Ma) from an
isochron of Lunar rocks. | Source: | arXiv, 1109.4805 | Services: | Forum | Review | PDF | Favorites |
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