Reconnaissance rubidium—strontium geochronology of New Zealand plutonic and metamorphic rocks

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Abstract A reconnaissance rubidium-strontium geochronological study of the plutonic and metamorphic rocks of the South Island and Stewart Island, New Zealand, shows that many of these deep-seated rocks have mineral ages that fall within the narrow limits of 98-119 million vears. In this grouping are rocks associated with the Separation Point Granite, the Charleston Gneiss, the Fiordland — southern Stewart Island Complex, and the Otago Schists. The metamorphism of the Otago Schists has heretofore been related to the Rangitata Orogeny on geological grounds; the present work suggests that this orogeny is of mid-Cretaceous age and was associated with the production of plutonic rocks over a wide area of the South Island.