Trace Element Models: Melting, Crystallization and Magma Mixing in Geochemistry - Prof. Na, Assignments of Geology

GEOL 567 Name___________________________________

Global Geochemical Systems

Problem Set Two

Trace Element Models: Melting and Crystallization

50 points

Due 2 March 05

Part One: Mantle Melting

Using the bulk composition, eutectic composition, initial concentrations of Ni, Rb, Ba,

and Sr, and partition coefficients in Tables 1 and 2, calculate the trace element compositions of

(F, Ni, Rb...)

Write an abstract summarizing the results (incompatible element enrichments and

compatible element depletions, relative enrichments as a function of partition coefficient,

element ratios that are useful to describe partial melting relations, .......)

Part Two: Fractional Crystallization of Basalt

Choose one partial melt (basalt) calculated in Part One. Calculate the concentrations of

Ni, Ba, Rb, and Sr during fractional crystallization consistent with a 2:1 plagioclase/olivine

phenocryst assemblage (67% plag and 33% ol), using the partition coefficients in Table 2.

Plot the results on the following diagrams:

F vs. CL/Co for all four elements

Part Three: Application: Fractional Crystallization or Magma Mixing??

REE data for Taos Plateau basalts, andesites, and a dacite exposed in the Red River

Gorge near Questa, NM are reproduced in Table 3 (McMillan and Dungan, 1986, JGR, 91:6029-

6045). Plot these data on a chondrite-normalized REE diagram.

Calculate and compare models of fractional crystallization and magma mixing for the