GEOL 4063 - Principles of Geochemistry Spring 2008 Profs. G. S. Mattioli & R. K. Davis, Department of Geosciences, University of Arkansas Homework Set #6: Clay mineralogy, cation exchange, and trace elements Due Date: Monday, April 28, 2008 at the start of class 1) Assume the following two different mantle mineralogies: a) 65% olivine, 20% orthopyroxene, and 15% clinopyroxene; and b) 60% olivine, 15% orthopyroxene, 20% clinopyroxene, and 5% garnet. Calculate the Bulk distribution coefficient (D*) for the REE's using the mineral-melt partition coefficients in Table 4.6. Plot D* as a function of increasing atomic number from La57 to Lu71 for the two different mineralogies (a and b). 2) Use a batch melting model with F = 0.01, 0.10, 0.25, and 0.50 and the D* for each mineralogy in part 1 to determine the (REE)CH to determine the CL/CO for each REE. Plot each model (F) CL/CO and CS/CO as function of increasing atomic number from La57 to Lu71. Assume that the mantle’s primordial REE composition was 1.5 times the chondritic abundances. Describe the different patterns. Batch melting equations: 3. Determine the electrical charges of the octahedral and tetrahedral layers and check whether the exchangeable ions balance the charge in the following clay mineral. [(Fe3+1.345Mg0.595Mn0.004)(Si3.836Al0.112Fe3+0.051)O10(OH)2]K0.779Ca0.076 4. Compare and contrast kaolinite and montmorillinite in terms of structure and properties. Be as specific as possible. 5. What is the primary difference between vermicullite and chlorite?? How does this effect the properties of these clay