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Regional volcanism of northern Zealandia: post-Gondwana break-up magmatism on an extended, submerged continent

By
N. Mortimer
N. Mortimer
GNS Science, Dunedin, New Zealand
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P. B. Gans
P. B. Gans
Department of Earth Science, University of California, Santa Barbara, USA
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S. Meffre
S. Meffre
Department of Earth Sciences, University of Tasmania, Hobart, Australia
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C. E. Martin
C. E. Martin
Department of Geology, University of Otago, Dunedin, New Zealand
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M. Seton
M. Seton
School of Geosciences, University of Sydney, Australia
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S. Williams
S. Williams
School of Geosciences, University of Sydney, Australia
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R. E. Turnbull
R. E. Turnbull
GNS Science, Dunedin, New Zealand
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P. G. Quilty
P. G. Quilty
Department of Earth Sciences, University of Tasmania, Hobart, Australia
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S. Micklethwaite
S. Micklethwaite
School of Earth, Atmosphere and Environment, Monash University, Melbourne, Australia
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C. Timm
C. Timm
GNS Science, Lower Hutt, New Zealand
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R. Sutherland
R. Sutherland
School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand
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F. Bache
F. Bache
Santos Ltd., Adelaide, Australia
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J. Collot
J. Collot
Service Geologique de Nouvelle Calédonie, Nouméa, New Caledonia
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P. Maurizot
P. Maurizot
Service Geologique de Nouvelle Calédonie, Nouméa, New Caledonia
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P. Rouillard
P. Rouillard
Service Geologique de Nouvelle Calédonie, Nouméa, New Caledonia
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N. Rollet
N. Rollet
Geoscience Australia, Canberra, Australia
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Published:
January 01, 2018

Abstract:

Volcanism of Late Cretaceous–Miocene age is more widespread across the Zealandia continent than previously recognized. New age and geochemical information from widely spaced northern Zealandia seafloor samples can be related to three volcanotectonic regimes: (1) age-progressive, hotspot-style, low-K, alkali-basalt-dominated volcanism in the Lord Howe Seamount Chain. The northern end of the chain (c. 28 Ma) is spatially and temporally linked to the 40–28 Ma South Rennell Trough spreading centre. (2) Subalkaline, intermediate to silicic, medium-K to shoshonitic lavas of >78–42 Ma age within and near to the New Caledonia Basin. These lavas indicate that the basin and the adjacent Fairway Ridge are underlain by continental rather than oceanic crust, and are a record of Late Cretaceous–Eocene intracontinental rifting or, in some cases, speculatively subduction. (3) Spatially scattered, non-hotspot, alkali basalts of 30–18 Ma age from Loyalty Ridge, Lord Howe Rise, Aotea Basin and Reinga Basin. These lavas are part of a more extensive suite of Zealandia-wide, 97–0 Ma intraplate volcanics. Ages of northern Zealandia alkali basalts confirm that a late Cenozoic pulse of intraplate volcanism erupted across both northern and southern Zealandia. Collectively, the three groups of volcanic rocks emphasize the important role of magmatism in the geology of northern Zealandia, both during and after Gondwana break-up. There is no compelling evidence in our dataset for Late Cretaceous–Paleocene subduction beneath northern Zealandia.

Supplementary material: Trace element compositions of zircons and whole-rock chemical compositions obtained by previous studies are available at: https://doi.org/10.6084/m9.figshare.c.3850975

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Contents

Geological Society, London, Special Publications

Large Igneous Provinces from Gondwana and Adjacent Regions

S. Sensarma
S. Sensarma
University of Lucknow, India
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B. C. Storey
B. C. Storey
University of Canterbury, New Zealand
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The Geological Society of London
Volume
463
ISBN electronic:
9781786203441
Publication date:
January 01, 2018

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