New Zealand Journal of Geology and Geophysics abstracts
Field characteristics, petrography, and geochronology of the
Hohonu Batholith and the adjacent Granite Hill Complex,
North Westland, New Zealand
T. E. WAIGHT1*
S. D. WEAVER1
T. R. IRELAND2
R. MAAS3
R. J. MUIR4
D. SHELLEY1
1Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
2Research School of Earth Sciences
Australian National University
A.C.T. 0200, Canberra, Australia
3Victorian Institute of Earth and Planetary Sciences
School of Earth Sciences
La Trobe University
Bundoora, Victoria 3083, Australia
4Isotope Geology Unit
Scottish Universities Research and Reactor Centre
East Kilbride
Glasgow, G75 OQU, United Kingdom
*Present address: Victorian Institute of Earth and Planetary
Sciences, School of Earth Sciences, La Trobe University, Bundoora, Victoria
3083, Australia.
Abstract Detailed geological mapping, petrography,
geochemistry, and geochronological studies in the Hohonu Batholith, North
Westland, have identified 10 granitoid plutons emplaced during three intrusive
episodes. The earliest episode is represented by a single dated Paleozoic
pluton, Summit Granite (new) (381.2 +/- 7.3 Ma), which is
correlated with a discrete pulse of Mid-Late Devonian plutonism recognised in
the Karamea Batholith. The undated Mount Graham Granite (new) is also
likely to be Paleozoic, based on chemical and petrographic characteristics.
The bulk of the batholith (seven plutons) was emplaced in the mid Cretaceous
(114-109 Ma) and comprises two related, yet distinct, geochemical suites,
which correlate with the previously defined Rahu Suite. The plutons identified
are (from north to south): Pah Point Granite; Jays Creek Granodiorite
(new); Uncle Bay Tonalite; Te Kinga Monzogranite; Deutgam Granodiorite;
Turiwhate Granodiorite (new); and Arahura Granite (new).
Mid-Cretaceous plutonism in the Western Province is considered to be the result
of crustal thinning and extension following overthickening during collision of
the Early Cretaceous Median Tectonic Zone volcanic arc.
Late Cretaceous alkaline activity is represented by the emplacement of the
A-type French Creek Granite at 81.7 +/- 1.8 Ma, contemporaneous with
intrusion of a major swarm of doleritic-lamprophyric dikes--the Hohonu Dike
Swarm. These events correlate with the first appearance of oceanic crust in
the Tasman Sea.
The Granite Hill Complex is a suite of amphibolite facies gneisses occurring
as an uplifted wedge between the Alpine Fault and the Hohonu Batholith. These
gneisses are considered to represent an extension of the Fraser Complex to the
south. A detailed understanding of their geological affinities and history is
yet to be established.
Keywords granitoids; geochronology; Hohonu Batholith; Jays
Creek Granodiorite; Pah Point Granite; Uncle Bay Tonalite; Te Kinga
Monzogranite; Deutgam Granodiorite; French Creek Granite; Turiwhate
Granodiorite; Summit Granite; Arahura Granite; Mt Graham Granite; Rahu Suite;
U-Pb zircon dating; Rb-Sr isotope data; Hohonu Dike Swarm; Granite Hill
Complex; Fraser Complex; new stratigraphic names
New Zealand Journal of Geology and Geophysics, 1997, Vol. 40: 1-17
0028-8306/97/4001--0001 $2.50/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (1776K); (scanned from paper original: notes about this process)
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