Downloaded from http://sp.lyellcollection.org/ by guest on January 31, 2019 Regional volcanism of northern Zealandia: post-Gondwana break-up magmatism on an extended, submerged continent N. MORTIMER1*, P. B. GANS2, S. MEFFRE3, C. E. MARTIN4, M. SETON5, S. WILLIAMS5, R. E. TURNBULL1, P. G. QUILTY3, S. MICKLETHWAITE6, C. TIMM7, R. SUTHERLAND8, F. BACHE9, J. COLLOT10, P. MAURIZOT10, P. ROUILLARD10 & N. ROLLET11 1GNS Science, Dunedin, New Zealand 2Department of Earth Science, University of California, Santa Barbara, USA 3Department of Earth Sciences, University of Tasmania, Hobart, Australia 4Department of Geology, University of Otago, Dunedin, New Zealand 5School of Geosciences, University of Sydney, Australia 6School of Earth, Atmosphere and Environment, Monash University, Melbourne, Australia 7GNS Science, Lower Hutt, New Zealand 8School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand 9Santos Ltd., Adelaide, Australia 10Service Geologique de Nouvelle Calédonie, Nouméa, New Caledonia 11Geoscience Australia, Canberra, Australia *Correspondence:
[email protected] 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-pro- gressive, 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.