Date of Award


Degree Type


Degree Name

Master of Science (MS)




Professor J. H. Crocket


The major and trace element geochemistry together with the Rb-Sr isotopic data indicate the Stephen Lake Pluton and Kakagi Lake volcanic suite to be possible differentiates of parent magmas of similar composition.

A co-magmatic origin of plutonic and volcanic felsic rocks is weakly suggested by normative mineral differentiation trends, major element similarities, K/Rb, Rb/Sr and Rb/Sr/Ba ratios and by differences in K, Rb, Ba and Zr contents.

Sr isotopic analysis reveals that the Stephen Lake Pluton possesses an initial ratio of 0.7015 ± 0.0007 and an isochron age of 2534 ± 96 Ma. The low initial ratio reflects a basaltic magma source and the introduction of new material into the crust at this time. The Kakagi Lake acid volcanic suite scatters about a reference isochron of 2600 Ma with a low initial ratio. The distinctive low initial ratios of both the pluton and the volcanics are strongly suggestive of a percentage of similar composition.

Comparison with surrounding granitoid plutons of the same age suggest the source region was heterogeneous with Rb/Sr ratios ranging from 0.020 to 0.035.

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