Geology of the Omoeroa Range and Canavan's Knob, South Westland
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In the eastern part of the Omoeroa Range (a small range west of the Alpine Fault and south of Franz Josef) a 2-pyroxene monzo-granodiorite pluton was found to have intruded meta sediments of the Greenland Group.
The Greenland Group has undergone three phases of deformation, a dominant earlier event was prior to the intrusion of the monzogranodiorite and the 2nd one has resulted in small crenulations and deformation of contact metamorphic biotite porphyroblasts. The maximum grade of contact metamorphism seen is pyroxene hornfels fades.
A later series of diopside-hornblende gabbro plugs has intruded both the Greenland Group and the monzo- granodiorite. Field relations, petrography and geochemistry show that calc-alkaline lamprophyre dikes and porphyritic granite dikes are related to the gabbro plugs while monzo-diorite dikes, pegmatite dikes and a high-K hornblende andesite dike (with similar chemistry to the monzo-granodiorite) are related to the monzo-granodiorite.
Chemistry of both suites of intrusions suggest association with a subduction zone or zones, however, no ages are known.
Later uplift and erosion have been followed by extensive glaciation during the Pleistocene, which has left glacial deposits (moraines, tills and lacustrine sediments) covering most of the area.
The Greenland Group has undergone three phases of deformation, a dominant earlier event was prior to the intrusion of the monzogranodiorite and the 2nd one has resulted in small crenulations and deformation of contact metamorphic biotite porphyroblasts. The maximum grade of contact metamorphism seen is pyroxene hornfels fades.
A later series of diopside-hornblende gabbro plugs has intruded both the Greenland Group and the monzo- granodiorite. Field relations, petrography and geochemistry show that calc-alkaline lamprophyre dikes and porphyritic granite dikes are related to the gabbro plugs while monzo-diorite dikes, pegmatite dikes and a high-K hornblende andesite dike (with similar chemistry to the monzo-granodiorite) are related to the monzo-granodiorite.
Chemistry of both suites of intrusions suggest association with a subduction zone or zones, however, no ages are known.
Later uplift and erosion have been followed by extensive glaciation during the Pleistocene, which has left glacial deposits (moraines, tills and lacustrine sediments) covering most of the area.
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106 leaves : ill., maps ; 30 cm.
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1984Wooding
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POLYGON ((170.117459884000027 -43.422410954999975,170.103157593000105 -43.427766602999952,170.088561050000067 -43.406053441999973,170.075300399000071 -43.386312489999966,170.128214728000103 -43.367754220999984,170.15665427600004 -43.374505383999974,170.159070939000117 -43.377226556999972,170.168524222000087 -43.387868171999969,170.153879370000027 -43.398495537999963,170.135265061000041 -43.398086992999936,170.132508690000122 -43.413063096999963,170.131775080000011 -43.417047689999947,170.117459884000027 -43.422410954999975))
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Wooding, A. C., “Geology of the Omoeroa Range and Canavan's Knob, South Westland,” Otago Geology Theses, accessed May 19, 2025, https://theses.otagogeology.org.nz/items/show/183.