THE UNIVERSITY OF WESTERN ONTARIO

LONDON CANADA

Mid-Term Test - February 13th 1998

Time: 50 mins Intramural

GEOLOGY 300B

1) The equation C_x = C_o/(K - X(K-1)) is the standard form describing variations in element concentration during fractionation processes.

a) What do the variables C_x, C_o, X, and the parameter K represent? (2)

b) In igneous fractionation processes, what special circumstances are represented by values for K of 0, 1 and infinity. (3)

2) a) Explain the concept of element compatibility in fractionation processes. (3)

b) what trace elements are compatible with: (3)

plagioclase;

garnet;

magnetite.

3) Draw the relationship you would expect to find in an X-Y plot of:

a) an incompatible element versus an incompatible element. (3)

b) a compatible element versus an incompatible element.

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c) Give an example of a ratio plot used to delineate mineral |

fractionation: (3) |

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4) a) what triangular plot would you use to conveniently discriminate between ocean ridge, plume, and arc rocks? Label the fields. (3)

5) What acronyms are commonly used to refer to: (4)

basaltic magma extruded at oceanic ridges;

primitive island arcs;

mature island arcs;

Archean age ultramafic rocks

6) Draw the shape (pattern) of:

a) a chondrite normalized spidergram representing basaltic rocks derived from a depleted mantle source. (3)

b) a mature arc spidergram with values normalized against ocean ridge basalt. (3)

7) a) What is meant by the acronym SMOW and the term d ¹⁸O? (2)

b) What controls sulphur isotope fractionation? (2)

c) What controls carbon isotope fractionation? (2)

8) a) What fudamental rate equation describes the process of radioactive disintegration? (2)

b) What are model ages ?(5)

9) a) List the major elements in standard order of valency. (2)

b) Give the name and formulae of the end members of olivine; name two other normative crustal minerals. (2)

c) In what minerals do Na, K, and Al reside in the mantle? (3)

10) a) Name the dominant fractionation and mixing processes operating within the Earth System cycle(s). (5)

b) how is calcium distributed within the Earth system? (5)

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