Abstract Passive continental margins are commonly classified as magma-poor and magma-rich types. Related breakup processes are often associated with far-field tectonic stresses or upwelling mantle plumes. The Chatham Rise east off New Zealand records a sequence of Late Cretaceous tectonic events, which include subduction and collision of the oceanic Hikurangi Plateau to subsequent continental rifting and breakup. The mechanisms triggering the change in tectonic forces are poorly understood but address open questions regarding the formation of passive margins. We acquired wide-angle seismic reflection/refraction, multi-channel seismic and potential field data along three profiles crossing the southern Chatham Rise margin and SE Chatham Terrace to the oceanic crust in order to image and understand the crustal structure and breakup mechanisms. Variations in crustal thickness along the highly faulted Chatham Rise are most likely related to the collision with the Hikurangi Plateau. Our data indicate that the SE Chatham Terrace represents a broad continent-ocean transition zone (COTZ), which we interpret to consist of very thin continental crust affected by magmatic activity. Along the southern Chatham Rise margin, features of both, magma-poor and magma-rich rifted margins are present. We suggest that passive rifting initiated at 105–100 Ma related to slab dynamics after the Hikurangi Plateau collision. We revise the onset of seafloor spreading south of the eastern Chatham Rise to ~88 Ma from the extent of our inferred COTZ. Geographically extensive, but low-volume intraplate magmatism affected the margin at 85–79 Ma. We suggest that this magmatism and the onset of seafloor spreading are a response to upwelling mantle through a slab window after 90 Ma. After 85 Ma, spreading segments became connected leading to the final separation of Zealandia from Antarctica. We interpret the southern Chatham Rise margin as a unique hybrid margin whose tectonic history was influenced by passive continental rifting and mantle upwelling.

中文翻译：

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查塔姆海隆南部边缘的白垩纪大陆内裂谷和西兰洲和南极洲之间海底扩张的初始化

摘要 被动大陆边缘通常分为贫岩型和富岩型。相关的破裂过程通常与远场构造应力或上涌的地幔柱有关。新西兰东部查塔姆海隆记录了一系列晚白垩世构造事件，其中包括海洋希库朗伊高原的俯冲和碰撞，以及随后的大陆裂谷和破裂。引发构造力变化的机制知之甚少，但解决了有关被动边缘形成的开放性问题。我们沿着跨越查塔姆海隆南部边缘和查塔姆台地东南部到大洋地壳的三个剖面获取了广角地震反射/折射、多道地震和势场数据，以便对地壳结构和破裂机制进行成像和了解。沿高度断层的查塔姆隆起的地壳厚度变化很可能与与希库朗伊高原的碰撞有关。我们的数据表明 SE Chatham Terrace 代表了一个广阔的大陆 - 海洋过渡带 (COTZ)，我们认为它由受岩浆活动影响的非常薄的大陆地壳组成。沿着查塔姆隆起南部边缘，存在着贫岩浆和富岩浆裂谷边缘的特征。我们建议在 105-100 Ma 开始的被动裂谷与 Hikurangi 高原碰撞后的板块动力学有关。我们将查塔姆海隆东部以南海底扩张的开始时间从我们推断的 COTZ 的范围修改为 ~88 Ma。地理范围广泛但体积较小的板内岩浆作用影响了 85-79 Ma 的边缘。我们认为，这种岩浆活动和海底扩张的开始是对 90 Ma 之后通过板块窗口的上涌地幔的反应。85 Ma 之后，扩张段连接起来，导致西兰洲与南极洲最终分离。我们将查塔姆海隆南部边缘解释为一个独特的混合边缘，其构造历史受到被动大陆裂谷和地幔上涌的影响。