New Zealand Journal of Geology
and Geophysics abstracts
40Ar/39Ar
ages of silicic volcanic rocks in the Tauranga-Kaimai area, New
Zealand: dating the transition between volcanism in the Coromandel Arc
and the Taupo Volcanic Zone
R. M. Briggs
Department of Earth Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand
B. F. Houghton*
Institute of Geological
& Nuclear Sciences
Wairakei Research Centre
Private Bag 2000
Taupo, New Zealand
M. McWilliams
Department of Geological and
Environmental Sciences
Stanford University
Stanford, California 94305-2115, USA
C. J. N. Wilson†
Institute of Geological
& Nuclear Sciences
Gracefield Research Centre
P.O. Box 30 368
Lower Hutt, New Zealand
*Present address: Department
of Geology and Geophysics, SOEST, University of Hawaii at Manoa,
Honolulu, Hawaii 96822.
†Department
of Geology, University of Auckland, Private Bag 92
019, Auckland.
Abstract Subduction-related
volcanism in the northern part of the North Island of New Zealand
shifted abruptly during the late Pliocene. This study focuses on the
transition, in time and space, from the NNW-oriented Miocene–Pliocene
Coromandel Volcanic Zone to the northeast-oriented active Taupo
Volcanic Zone. The volcanic rocks marking this transition are exposed
in the Tauranga Basin and adjacent Kaimai Range, and associated here
with the recently defined Tauranga and Kaimai Volcanic Centres,
respectively. New 40Ar/39Ar
age determinations indicate that the transition occurred between 1.90
and 1.55 Ma, that is between the youngest age of silicic
volcanism in the Tauranga-Kaimai area, and the age of the oldest
silicic volcanism in the Taupo Volcanic Zone. This interpretation is
generally consistent with recent plate models and with the initiation
of the Kermadec Arc within the last 2 m.y.
Keywords 40Ar/39Ar;
silicic volcanism; Tauranga Volcanic Centre; Kaimai Volcanic Centre;
Pliocene; Pleistocene; Aongatete Ignimbrites; Waiteariki Ignimbrite;
Papamoa ignimbrites; Hauraki Fault
G04014; Received 19 March 2004;
accepted 8 February 2005; Online publication date 22 August 2005
New Zealand Journal of Geology
& Geophysics, 2005, Vol. 48:
459–469
0028–8306/05/4803–0459© The Royal Society of New Zealand 2005
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