Publication Date:
2022-01-31
Description:
Highlights
• New 40Ar/39Ar dates from SW Pacific and Zealandia igneous rocks form the basis of a revised tectonic model.
• Intraplate lavas erupted onto continental, LIP and oceanic crust from 99 to 78 Ma.
• Spreading ridges and transforms adjusted themselves around a collided Hikurangi Plateau.
• Kinematically stable Pacific-Antarctic spreading became established from c. 84 Ma.
• Osbourn Trough Sea floor spreading possibly ceased at c. 79 Ma.
Abstract
New 40Ar/39Ar ages of igneous rocks clarify the nature, timing and rates of movement of the oceanic Pacific, Phoenix, Farallon and Hikurangi plates against Gondwana and Zealandia in the Late Cretaceous. With some qualifications, cessation of spreading at the Osbourn Trough is dated c. 79 Ma, i.e. 30–20 m.y. later than 110–100 Ma Hikurangi Plateau-Gondwana collision. Oceanic crust of pre-84 Ma is confirmed to be present at the eastern end of the Chatham Rise, and a 99–78 Ma intraplate lava province erupted across juxtaposed Zealandia, Hikurangi Plateau and oceanic crust. We propose a new regional tectonic model in which a mechanically jammed Hikurangi Plateau resulted in the dynamic propagation of small, kinematically misaligned short-length 110–84 Ma spreading centres and long-offset fracture zones. It is only from c. 84 Ma that geometrically stable spreading became localized at what is now the Pacific-Antarctic Ridge, as Zealandia started to split from Gondwana.
Type:
Article
,
PeerReviewed
Format:
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