Thermal plume models and melt generation in East Africa: A dynamic modeling approach
Thermal plume models and melt generation in East Africa: A dynamic modeling approach
复制标题
东非的热羽流模型和熔体生成：动态建模方法
DOI：
10.1016/j.epsl.2005.04.049
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发表时间：
2005
影响因子：
5.3
通讯作者：
P. V. Keken
中科院分区：
文献类型：
--
作者：
Shu;B. Kuo;L. Chiao;P. V. Keken
热液柱对东非新生代岩浆活动有贡献的假说现在已被广泛接受。争议在于有多少羽状物存在，以及它们可能位于何处。在这项研究中，我们展示了一些热羽流模型的地幔对流模型的数值实验，并讨论了在东非的熔体生成的影响。我们研究了地幔柱、坦桑尼亚克拉通和非洲岩石圈结构如何相互作用，从而导致始新世以来东非的岩浆活动分布。我们的研究结果表明，岩石圈的可变厚度调制熔体的产生。单羽流模式无法一致地再现观测结果。在阿法尔和肯尼亚地区的羽流双羽流模型是可行的合理的物理特性。然而，当非洲板块移动时，地幔柱物质的分布对坦桑尼亚克拉通和厚岩石圈区域接近地幔柱的角度很敏感。模型，有今天的位置的第二个羽（肯尼亚羽）下的东部裂谷或内部的坦桑尼亚克拉通可以最好地匹配玄武岩的分布。我们的模型结果表明，玄武岩喷发与阿法尔羽水龙头的羽体在一般情况下，而熔化发生在较浅的深度为肯尼亚羽除了始新世情节。岩浆作用来自埃塞俄比亚西北部低钛玄武岩省的更贫化的地幔源。我们的实验表明，阿法尔羽的热影响，但预测没有羽源熔体，这表明在岩石圈内的阿法尔羽在这一地区的热影响触发的熔体生成。我们的模型结果表明，在东非裂谷过程的启动，羽起着积极的作用。
The hypothesis that thermal plumes contribute to the Cenozoic magmatism in East Africa is now widely accepted. The controversy lies on how many plumes exist and where they may be located. In this study we show numerical experiments of mantle convection models for a number of thermal plume models and discuss the implications for the melt generation in East Africa. We investigate how the plume(s), the Tanzania craton, and the African lithospheric structure may interplay to result in the magmatism distribution in East Africa since the Eocene. Our results demonstrate that the variable thickness of the lithosphere modulates melt generation. A single-plume model cannot reproduce the observations consistently. Double-plume models with plumes located at Afar and Kenya regions are viable with reasonable physical properties. The distribution of the plume material, however, is sensitive to the angle at which the Tanzania craton and regions of thick lithosphere approach the plume, as the African plate moves. Models that have present-day location of the second plume (Kenya plume) under the Eastern rift or the interior of the Tanzania craton can best match the basalt distribution. Our model results suggest that the basaltic eruptions associated with the Afar plume tap a relatively deep source of the plume body in general, whereas melting occurs at shallower depths for the Kenya plume except for the Eocene episode. The magmatism is derived from a more depleted mantle source in the low-Ti basalt province of northwestern Ethiopia. Our experiments indicate the thermal influence of the Afar plume but predict an absence of plume-derived melts, suggesting the melt generation within lithosphere triggered by thermal influence of Afar plume in this region. Our model results suggest that plume plays an active role on the initiation of the rifting process in East Africa.