Geology of the Green Lake area, Eastern Fiordland, New Zealand.

Higgins, Neville Charles.

An area of high grade basement terrain is described from the Green Lake area, Eastern Fiordland. The crystalline complex is mapped in three groups - The Metamorphic group, containing quartzo-feldspathic schists and gneisses; The Syntectonic intrusive group, consisting of gneisses of dioritic to tonalitic composition which concordantly intrude the Metamorphic group (Within this group occurs a gneissic aegirine granite, an unusual rock type, the origin of which is discussed.); The Post-tectonic intrusive group, made up of discordant stocks of diorite and a granodiorite batholith which intrude the complex and postdate the main regional metamorphic episode of epidote-amphibolite grade.
Contact metamorphic effects, that reached hornblende hornfels facies, are observed at some of the boundaries of the granodiorite batholith.
Microcline megacrysts from the granodiorite are investigated, using experimental data and microprobe analysis, and a mechanism involving pTessure variation during crystallisation is suggested for their origin.
An exsolution hypothesis for the formation of myrmekite in the granodiorite is indicated from microprobe analysis.
Shallow water tertiary sediments are deposited on the eastern edge of the granodiorite batholith.
Faulting is extensively developed in the area and one major fault, the Fiordland Boundary fault is of regional significance. Structurally the rocks strike North-South and dip to the west.
The Green Lake suite of rocks is similar to those mapped by Turner in 1938 in the eastern Manapouri region.

90 p. : illus. (part col.), maps (2 col. in pocket) ; 30 cm.

1975Higgins

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