Fritz H, Abdelsalam M, Ali K A, Bingen B, Collins A S, Fowler A R, Ghebreab W, Hauzenberger C A, Johnson P R, Kusky T M, Macey P, Muhongo S, Stern R J, Viola G
Department of Earth Sciences, University of Graz, 8010 Graz, Heinrichstrasse 26, Austria.
Boone Pickens School of Geology, Oklahoma State University, Noble Research Center, Stillwater, OK 74078, USA.
J Afr Earth Sci. 2013 Oct;86:65-106. doi: 10.1016/j.jafrearsci.2013.06.004.
The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world́s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara-Congo-Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian-Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite-Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650-620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo-Tanzania-Bangweulu Cratons and the Zimbabwe-Kalahari Craton. They closed during the ∼600-500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600-550 Ma extension is recorded in the Arabian-Nubian Shield and the Eastern Granulite-Cabo Delgado Nappe Complex. Later ∼550-480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings resulted in the evolution of distinctly different orogen styles. The Arabian-Nubian Shield is an accretion-type orogen comprising a stack of thin-skinned nappes resulting from the oblique convergence of bounding plates. The Eastern Granulite-Cabo Delgado Nappe Complex is interpreted as a hot- to ultra-hot orogen that evolved from a formerly extended crust. Low viscosity lower crust resisted one-sided subduction, instead a sagduction-type orogen developed. The regions of Tanzania and Madagascar affected by the Kuungan Orogeny are considered a Himalayan-type orogen composed of partly doubly thickened crust.
东非造山带从北部的以色列南部、西奈半岛和约旦延伸至南部的莫桑比克和马达加斯加，是世界上最大的新元古代至寒武纪造山杂岩。它由西部太古宙撒哈拉-刚果-卡拉哈里克拉通和东部新元古代印度之间的各个洋域和大陆碎块拼贴而成。造山带的固结在约8.5亿年至5.5亿年前不同的造山阶段完成。造山带的北部，即阿拉伯-努比亚盾，主要是在莫桑比克洋及其附近形成的新生的新元古代地壳。该海洋在约8.5亿年至6.2亿年前漫长的岛弧和微大陆增生期关闭。在阿拉伯-努比亚盾以南，肯尼亚南部、坦桑尼亚和莫桑比克的东粒岩-德尔加杜角推覆体杂岩是在莫桑比克洋附近形成的伸展地壳，并经历了约6.5亿年至6.2亿年前的麻粒岩相变质作用。约6.2亿年前推覆体组合的完成被定义为东非造山运动，与莫桑比克洋的关闭有关。在6.2亿年后，南极洲东部、印度、刚果-坦桑尼亚-班韦乌卢克拉通南部和津巴布韦-卡拉哈里克拉通之间仍存在海洋。它们在约6亿年至5亿年前的库恩甘或马达加斯加造山运动期间关闭，这是一次构造热事件，影响了坦桑尼亚南部、赞比亚、马拉维、莫桑比克、马达加斯加和南极洲的大部分地区。东非和库恩甘造山运动之后是造山后伸展阶段。约6亿年至5.5亿年前的早期伸展作用记录在阿拉伯-努比亚盾和东粒岩-德尔加杜角推覆体杂岩中。约5.5亿年至4.8亿年前的后期伸展作用影响了莫桑比克和马达加斯加南部。尽管这两个伸展阶段是穿时的，但都被解释为岩石圈拆沉的结果。沿着东非造山带的走向，不同的地球动力学背景导致了截然不同的造山带样式的演化。阿拉伯-努比亚盾是一个增生型造山带，由边界板块斜向汇聚形成的一系列薄皮推覆体组成。东粒岩-德尔加杜角推覆体杂岩被解释为一个从先前伸展地壳演化而来的热至超热造山带。低粘度的下地壳阻止了单侧俯冲，相反形成了一个沉降俯冲型造山带。受库恩甘造山运动影响的坦桑尼亚和马达加斯加地区被认为是一个喜马拉雅型造山带，由部分双重加厚的地壳组成。
