Abstract

Based on geological and geophysical data for the conjugate Africa–East Antarctica margins, the peculiarities of preparation of the breakup of central Gondwana are discussed. When using the historical approach, a significant inheritance of the Middle-Upper Jurassic tectono-magmatic development from the preceding time is shown. The first location of tectono-magmatic activity in zones of weakness on the proximal margin, its subsequent migration to distal margins, and further opening of the ocean is established. The geochemical features of magmas of the region and their sources are discussed. Evidence is presented for the decisive influence of the Karoo–Maud plume on the development of magmatism. A significant feature of plume manifestation is considered: the presence of high-magnesian ferruginous picrites, formed by melting of a pyroxenite source with specific composition, coinciding with the central part of the plume and corresponding to the earliest eruptions. We determined the source of magmatism at the initial stage could have been the substance of a rising plume, and magmas reached the surface through existing fractures without interacting with the lithosphere. In the course of evolution, the admixture of pyroxenites in the source decreased and the melts acquired the features of melting lithospheric mantle, which was reflected in the isotopic characteristics of melts with a predominant enriched EM2 component. The structure and magmatism of the Southern Ocean and South Atlantic are compared. Also discussed the locations of the Mesozoic Karoo–Maud and Tristan plumes, as well as the zones of subsequent breakup of Gondwana, above the margins of the African superplume, indicating a relationship between surface and deep-seated events.

中文翻译：

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非洲-南极东部地区南洋被动边缘的构造

摘要

基于非洲-南极共轭边缘的地质和地球物理数据，讨论了冈瓦纳中部破裂准备的特殊性。当使用历史方法时，显示了从上一次以来中上侏罗世构造岩浆发育的重要传承。建立了构造－岩浆活动的第一个位置，即近端边缘的薄弱区域，随后向远端边缘的迁移以及海洋的进一步开放。讨论了该地区岩浆的地球化学特征及其来源。提出了Karoo-Maud羽对岩浆作用发展具有决定性影响的证据。羽状流表现的一个重要特征被认为是：高镁质铁质苦味酒的存在，通过熔化具有特定成分的辉石矿源而形成，与烟羽的中心部分重合并且对应于最早的喷发。我们确定了岩浆作用在最初阶段的来源可能是羽状上升的物质，并且岩浆通过现有的裂缝到达了地表而没有与岩石圈相互作用。在演化过程中，辉石岩在源中的混合减少，熔体获得了岩石圈地幔熔融的特征，这反映在具有富集了EM2成分的熔体的同位素特征中。比较了南大洋和南大西洋的构造和岩浆作用。还讨论了中生代Karoo–Maud和Tristan羽状流的位置，以及冈瓦纳随后解体的区域，