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Problems
1. Assuming the Earth has a CI chondritic composition, and using the values for the mass of the core
and the mass of the mantle in Table 11.1 and the partition coefficients in Table 11.4, calculate what
the concentrations of Re, Ir, Mo, and Ag should be in the bulk silicate Earth if the core formed by an
equilibrium process. Compare you results with the primitve mantle values in Table 11.3.
2. Calculate new bulk silicate Earth concentrations of Re, Ir, Mo, and Ag by adding 1% CI chondritic
material to your results from Problem 1. Again compare these results with primitive mantle values
of Table 11.3.
87
3. Assume that the bulk silicate Earth has a Sr/86Sr ratio of 0.705, and Sr concentration of 20 ppm.
Calculate the bulk silicate Earth Rb/Sr ratio.
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Chapter 11: The Mantle and Core
4. Suppose a rising mantle plume is 220¡ hotter than surrounding mantle and that the ³ -olivineÐMg-
perovskite transition occurs at 600 km depth in the surrounding mantle. Assume a homgeneous man-
tle density of 3.5 g/cc at 660 km and above. At what depth does the ³ -olivineÐMg-perovskite tran-
sition occur within the mantle plume?
5. Whether the ³ -olivineÐMg-perovskite transition is endothermic or exothermic will affect mantle
convection (i.e., sinking of lithospheric slabs, rise of mantle plumes). Discuss why this is so, ex-
plaining the effects of both endothermic and exothermic phase transitions on rising mantle plumes
and sinking lithospheric slabs.
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Chapter 10: The Mantle and Core
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