Watts Emma J, Rees Rhiannon, Jonathan Philip, Keir Derek, Taylor Rex N, Siegburg Melanie, Chambers Emma L, Pagli Carolina, Cooper Matthew J, Michalik Agnes, Milton J Andrew, Hincks Thea K, Gebru Ermias F, Ayele Atalay, Abebe Bekele, Gernon Thomas M
School of Ocean and Earth Science, University of Southampton, Southampton, UK.
Present Address: Geography Department, Swansea University, Swansea, UK.
Nat Geosci. 2025;18(7):661-669. doi: 10.1038/s41561-025-01717-0. Epub 2025 Jun 25.
Mantle upwellings drive large-scale surface volcanism and facilitate continental breakup and ocean basin formation. However, the spatial characteristics and internal composition of these upwellings alongside how they are modified by plate tectonics are poorly resolved. Afar, East Africa, is a classic triple junction comprising three rifts at various stages of evolution thought to be underlain by a mantle upwelling or plume, allowing examination of the controls on the mantle upwelling. Here we present geochemical data from >130 samples of 'young' volcanoes spanning the rifts defining the triple junction to show that the underlying mantle comprises a single, asymmetric upwelling. Using statistical modelling to integrate our data with existing geochemical and geophysical constraints, we suggest that Afar is fed by a spatially and chemically heterogeneous upwelling, which controls the composition and relative abundance of melt in all three rift arms. We identify repetitive signatures in mantle compositions in rift regions, whose variability is a longer wavelength in faster-extending rift arms. This suggests more rapid channelized mantle flow occurs where rifting rates are higher and the plate is thinner, aiding flow of the upwelling towards the faster-spreading Red Sea Rift. Our findings demonstrate how the evolution of mantle upwellings is influenced by the dynamics of overriding plates.
地幔上涌驱动大规模地表火山活动，并促进大陆裂解和大洋盆地形成。然而，这些上涌的空间特征、内部组成以及它们如何被板块构造所改变，目前仍不清楚。阿法尔地区位于东非，是一个典型的三联点，由处于不同演化阶段的三条裂谷组成，人们认为其下方存在地幔上涌或地幔柱，这使得对控制地幔上涌的因素进行研究成为可能。在此，我们展示了跨越界定三联点的裂谷的1 > 30个“年轻”火山样本的地球化学数据，结果表明其下方地幔由单一的不对称上涌构成。通过运用统计模型将我们的数据与现有的地球化学和地球物理约束条件相结合，我们认为阿法尔地区由一个在空间和化学性质上均不均匀的上涌提供物质，该上涌控制着所有三条裂谷臂中熔体的组成和相对丰度。我们在裂谷区域的地幔成分中识别出重复特征，其变化在扩展速度较快的裂谷臂中具有更长的波长。这表明在裂谷作用速率较高且板块较薄的地方，地幔流动的通道化速度更快，有助于上涌物质向扩张速度更快的红海裂谷流动。我们的研究结果表明了地幔上涌的演化是如何受到上覆板块动力学影响的。
