Abstract Two end-member scenarios have been proposed for the tectonic situation along the eastern margins of Gondwanaland before Zealandia was formed ca. 100 million years ago (Ma), namely: (1) A subduction zone located far from the eastern margin of Zealandia, wherein Zealandia may have separated from Gondwanaland by plume push of an active hotspot plume.; (2) A subduction zone located along the eastern margin of Gondwanaland, wherein Zealandia possibly separated from Gondwanaland via trench/subduction retreat. Assuming that the thermal structure of the deep mantle and source of hotspot plumes remained relatively stationary over the last hundred million years, major hotspot plumes with a large buoyancy flux did not exist under Zealandia; the eastern margins of Gondwanaland were far from two large low-shear-velocity provinces under the Africa–Atlantic and South Pacific regions. Herein, through numerical studies of three-dimensional global mantle convection, we examined the mantle convection and surface tectonic patterns at ~100 Ma. The present model considered the real configuration of Gondwanaland at the model surface to observe long-term variations of mantle convection and the resulting surface tectonic conditions. The results demonstrate that the extensive subduction zones developed preferentially along the eastern margin of Gondwanaland when the temperature anomaly of the lower mantle was primarily dominated by high-temperature regions under present-day Africa–Atlantic and South Pacific regions. The results of this study support one of the proposed hypotheses, where the breakup at the eastern margins of Gondwanaland at ~100 Ma occurred via trench/subduction retreat.

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来自地幔对流数值研究的大陆边缘破裂机制： 1. 冈瓦纳大陆东部边缘可能的构造模式

摘要 大约在西兰大陆形成之前，冈瓦纳大陆东部边缘的构造形势提出了两种端元情景。1亿年前（Ma），即：（1）位于西兰大陆东部边缘的俯冲带，其中西兰大陆可能通过活动热点羽流的羽流推动与冈瓦纳大陆分离。(2) 位于冈瓦纳大陆东缘的俯冲带，其中西兰岛可能通过海沟/俯冲后退与冈瓦纳大陆分离。假设过去一亿年深部地幔热结构和热点羽流来源保持相对稳定，则西兰大陆下不存在具有大浮力通量的主要热点羽流；冈瓦纳大陆的东部边缘远离非洲-大西洋和南太平洋地区下的两个大的低剪切速度省份。在这里，通过三维全球地幔对流的数值研究，我们检查了~100 Ma 的地幔对流和地表构造模式。本模型考虑了模型表面冈瓦纳大陆的真实构造，以观察地幔对流的长期变化和由此产生的地表构造条件。结果表明，当下地幔温度异常主要以当今非洲-大西洋和南太平洋地区的高温区为主时，广泛的俯冲带优先沿冈瓦纳大陆东缘发育。这项研究的结果支持提出的假设之一，