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Abstract
We present U–Pb zircon ages from a phosphate-cemented pebbly sandstone dredged from the central Lord Howe Rise and a 97 Ma rhyolite drilled on the southern Lord Howe Rise. Four granitoid pebbles from the sandstone give U–Pb ages in the range 216–183 Ma. Most detrital zircons in the bulk sandstone are also Late Triassic–Early Jurassic, but subordinate populations of Late Cretaceous and Precambrian zircons are present. The pebbly sandstone's highly restricted Late Triassic–Early Jurassic zircon population indicates the nearby occurrence of underlying basement plutons that are the same age as parts of the I-type Darran Suite, Median Batholith of New Zealand and supports a continuation of the Early Mesozoic magmatic arc northwest from New Zealand. Zircon cores from the southern Lord Howe Rise rhyolite do not yield ages older than 97 Ma and thus provide no information about older basement.
ACKNOWLEDGEMENTS
We thank the Captain, crew and science party of the Marion DuFresne 153 voyage for obtaining the conglomerate. Mineral separation was carried out by John Simes and Belinda Smith Lyttle, and an X-ray diffraction analysis was carried out by Debra Chappell. We have had useful discussions with Chris Adams and Hamish Campbell. The manuscript was improved by comments from Mark Rattenbury, Ron Hackney and Geoff Fraser, and by journal reviews from Kelsey Dadd and Dominique Cluzel. Mortimer, Turnbull and Tulloch acknowledge core research funding to GNS Science's Minerals, Urban and Regional Geology Programme provided by the Government of New Zealand. Rollet and Hashimoto publish with the permission of the Chief Executive Officer of Geoscience Australia.
Disclosure statement
No potential conflict of interest was reported by the authors.
SUPPLEMENTAL DATA FILE
Raw U–Pb zircon data for P63855, P81390 and P81391.