Abstract
Abstract Orthogneisses of granite, quartz monzonite, monzonite, and tonalite, collectively termed granitoid, occur locally as isolated enclaves within the Early Cretaceous granulite terrain (Western Fiordland Orthogneiss—WFO) in Fiordland, southwest New Zealand. Discordant U‐Pb zircon isotopic data (7 fractions) from four granitoid samples from enclaves at George Sound, define an upper intercept age of 341 ± 34 Ma that is interpreted as approximating the time of formation of the granitoid suite. The lower intercept age of 93 ± 37 Ma is interpreted as approximating the time of zircon isotopic disturbance by major episodic Pb loss. Isotopic disturbance probably accompanied high‐temperature conditions at the time of incorporation of the granitoid rocks into the WFO protolith, and during subsequent granulite meta‐morphism; both occurred in the interval c. 120–110 Ma. Five whole‐rock samples from enclaves at George Sound yield an apparent Rb‐Sr isochron age of 391 ± 48 Ma, in agreement with the zircon data, an...
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