Geology of the granulite and amphibolite facies gneisses of Doubtful Sound, Fiordland, New Zealand

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Abstract
The geology of 700 km2 of high-grade metamorphic rocks from Doubtful Sound, New Zealand, is described. Malaspina, Turn Point, and Waipero Cove Gneiss Zones, constituting the granulite, transition, and amphibolite zones of the basement, are separated by Doubtful Sound Thrust from the amphibolite facies cover, consisting of Kellard Point Gneisses, Deep Cove Gneisses, and Straight River Granite. The last was intruded into the cover during the Tuhuan metamorphism and has a whole rock Rb-Sr isochron age of 372 ± 12 m.y. B.P. Regionally important syn-metamorphic faults cut the cover and may link up to form another thrust. It is suggested that Tuhuan retrogressive metamorphism of granulite facies basement, which gave rise to the transition and amphibolite zones, occurred during progressive amphibolite facies metamorphism of the cover sequence. Synmetamorphic migmatites from the cover give a whole rock Rb-Sr isochron age of 388 ± 23 m.y. b.p. The unaffected granulite basement is thought to be Precambrian. Rangitata uplift, but not metamorphism, is recognised. Mylonitisation along the parallel to the coastal strip is related to Kaikoura( ?) movement on an extension of Alpine Fault.