8
Peter Stille and Graham Shields
t o d a y
|
,
i
i
t,
t,,55
Time (lO'yeors)
t o d a y
~ "
C
|
i
!
4
4.55
T i m e (10'years)
|
|
t,.58 x tO'years ago
t, x 70r years ago
- unfractior~41ed
* c r u s t a l form, a l i ~
- p r i m i t i v e
- f r a c t i o n 4 t e d
to,, Sm/~l ~
Cru~
t I I I
~,.qs Sat~ ] -- '- I a.,~Ka
~R41
Fig. 1.2. Illustration of various Sr and Nd isotopic evolution parameters for the Earth
discussed in the text.
much as its ]43Nd/144Nd counterpart in the mantle, whereas in the Rb-Sr system
the opposite was the case. As more rubidium is contained within the crust, more
radiogenic 87Sr is produced in the crust than in the mantle. Therefore, the crust
shows a higher S7Sr/86Sr ratio than the mantle
Peter Stille and Graham Shields
t o d a y
|
,
i
i
t,
t,,55
Time (lO'yeors)
t o d a y
~ "
C
|
i
!
4
4.55
T i m e (10'years)
|
|
t,.58 x tO'years ago
t, x 70r years ago
- unfractior~41ed
* c r u s t a l form, a l i ~
- p r i m i t i v e
- f r a c t i o n 4 t e d
to,, Sm/~l ~
Cru~
t I I I
~,.qs Sat~ ] -- '- I a.,~Ka
~R41
Fig. 1.2. Illustration of various Sr and Nd isotopic evolution parameters for the Earth
discussed in the text.
much as its ]43Nd/144Nd counterpart in the mantle, whereas in the Rb-Sr system
the opposite was the case. As more rubidium is contained within the crust, more
radiogenic 87Sr is produced in the crust than in the mantle. Therefore, the crust
shows a higher S7Sr/86Sr ratio than the mantle