Possible tectonic patterns along the eastern margin of Gondwanaland from numerical studies of mantle convection
Possible tectonic patterns along the eastern margin of Gondwanaland from numerical studies of mantle convection
复制标题
DOI：
10.1016/j.tecto.2020.228476
复制
发表时间：
2020-07
期刊：
影响因子：
2.9
通讯作者：
Masaki Yoshida;S. Saito;K. Yoshizawa
中科院分区：
文献类型：
--
作者：
Masaki Yoshida;S. Saito;K. Yoshizawa
对于西兰迪亚形成前冈瓦纳大陆东部边缘的构造情况，提出了两种端元情景，即：(1)西兰迪亚东部边缘有一个远离西兰迪亚的俯冲带，西兰迪亚可能是在活跃热点羽流的推动下与冈瓦纳大陆分离的；(2)位于冈瓦纳大陆东部边缘的俯冲带，西兰迪亚可能通过海沟/俯冲后退与冈瓦纳大陆分离。假设近亿年来深部地幔热结构和热点柱源相对稳定，则西兰洲下不存在浮力通量较大的主要热点柱；冈瓦纳大陆东部边缘远离非洲-大西洋和南太平洋地区下面的两个大的低剪切速度省。本文通过对三维全球地幔对流的数值研究，研究了~100 Ma的地幔对流和地表构造模式。该模型考虑了冈瓦纳大陆在模型表面的真实构造，以观测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，当下地幔温度异常以现今非洲-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。本研究的结果支持了一种假设，即冈瓦纳大陆东部边缘在~100 Ma的断裂是通过海沟/俯冲退缩发生的。
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.