Tsai-way Wu

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Eight granitic bodies from the Grenville Province of Ontario have been petrographically and geochemically studied. It is believed that these granitoids were associated with the Grenville Orogeny and have recorded a history of about 300 million years of magmatism in this region.;Mineralogically, except for the riebeckite-bearing hypersolvus granite of the Deloro Pluton, hornblende and biotite are major mafic minerals for the other subsolvus granitoids. Although chemical compositions are varied from one pluton to the other, the Grenville granitoids are characterized, in general, by high agpaitic indices and oxidation ratios.;Except that the Union Lake quartz diorite is consistently I-type granite and the Barber's Lake peraluminous granite is close to S-type granite, the remaining sampled granitoids fall within both I- and S-type categories. However, the peralkaline Deloro Pluton is an A-type analogue. It is reasonable to believe that the source rocks, P-T conditioned and geological settings of the Grenville granitoids differ from those granites of the Lachlan Mobile Belt of eastern Australia. REE modelling suggests most Grenville granitoids were from a deep source, either lower crust (granulite) or upper mantle (quartz elcogite). This is consistent with their lower strontium initial ratios and high K/Rb.;The close chemical resemblance with the Younger Granite of Nigeria from an extensional environment may imply the existence of a long term extensional regime during the development of the Grenville plutonism. This hypothesis agrees with the Grenville evolution model of opening and closure of the Bancroft - Renfrew aulacogen; the Grenville granitic terrain may thus be interpreted as products of Proterozoic "extension - contraction" cycles.



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