Homrighausen S, Hoernle K, Zhou H, Geldmacher J, Wartho J-A, Hauff F, Werner R, Jung S, Morgan J P
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany.
Institut für Geowissenschaften, Christian-Albrechts Universität zu Kiel, Ludewig-Meyn-Str. 10, 24118 Kiel, Germany.
Sci Adv. 2020 Jul 8;6(28):eaba0282. doi: 10.1126/sciadv.aba0282. eCollection 2020 Jul.
Age-progressive volcanism is generally accepted as the surface expression of deep-rooted mantle plumes, which are enigmatically linked with the African and Pacific large low-shear velocity provinces (LLSVPs). We present geochemical and geochronological data collected from the oldest portions of the age-progressive enriched mantle one (EMI)-type Tristan-Gough track. They are part of a 30- to 40-million year younger age-progressive hotspot track with St. Helena HIMU (high time-integrated U/Pb) composition, which is also observed at the EMI-type Shona hotspot track in the southernmost Atlantic. Whereas the primary EMI-type hotspots overlie the margin of the African LLSVP, the HIMU-type hotspots are located above a central portion of the African LLSVP, reflecting a large-scale geochemical zonation. We propose that extraction of large volumes of EMI-type mantle from the margin of the LLSVP by primary plume heads triggered upwelling of HIMU material from a more internal domain of the LLSVP, forming secondary plumes.
年龄递进式火山活动通常被认为是深部地幔柱的地表表现，而地幔柱与非洲和太平洋大型低剪切波速度省（LLSVP）存在神秘联系。我们展示了从年龄递进式富集地幔1（EMI）型特里斯坦-戈夫轨迹最古老部分收集的地球化学和地质年代学数据。它们是一个年龄递进式热点轨迹的一部分，比圣赫勒拿岛HIMU（高时间积分U/Pb）成分年轻3000万至4000万年，在最南端大西洋的EMI型绍纳热点轨迹也有观测到。虽然原生EMI型热点位于非洲LLSVP的边缘之上，但HIMU型热点位于非洲LLSVP的中心部分上方，反映了大规模的地球化学分带。我们认为，原生羽流头部从LLSVP边缘提取大量EMI型地幔，触发了HIMU物质从LLSVP更内部区域的上涌，形成了次生羽流。
