Superplumes, plates, and mantle magmatism in two‐dimensional numerical models
Superplumes, plates, and mantle magmatism in two‐dimensional numerical models
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DOI：
10.1029/2006jb004533
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发表时间：
2007-06
影响因子：
--
通讯作者：
Masaki Ogawa
中科院分区：
文献类型：
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作者：
Masaki Ogawa
[1]本文系统地建立了由不相容放射性元素加热的对流地幔中岩浆活动的二维数值模型。板块构造是自洽建模的一部分，对流的牛顿流体与温度和应力历史依赖的粘度驱动的热和成分浮力，而岩浆活动是模拟的玄武岩浆减压熔融产生的向上迁移。脊岩浆活动积极地发生化学分化的地幔，一个超级地幔柱是很好地发展在最低的地幔作为一个广泛的热区富含玄武岩成分，提供了岩石圈的机械强度足以抑制自发引发的俯冲由其自身的重量和内部加热速率足够高。热的窄柱体经常从超级柱体中上升，引起深部岩浆生成和热点岩浆作用，这反过来又经常引起新的板块边缘。频繁的板块边缘形成使板块构造活动相对稳定。地幔的热和化学状态也保持相当稳定。然而，随着内部加热速率变低，超级地幔柱的狭窄地幔柱变得零星和明显更冷，深层岩浆生成变得罕见;新的板块边缘形成变得不那么频繁。因此，板块构造活动和地幔的热化学状态变得随时间波动很大。这里模拟的地幔结构和地幔柱行为与从太古代到现在对地球的许多观测相匹配。
[1] Two-dimensional numerical models are systematically presented for magmatism in a convecting mantle internally heated by incompatible radioactive elements. Plate tectonics is self-consistently modeled as a part of convection of Newtonian fluid with temperature- and stress-history-dependent viscosity driven by thermal and compositional buoyancy, while magmatism is modeled as an upward migration of basaltic magma generated by decompression melting. Ridge magmatism actively takes place to chemically differentiate the mantle, and a superplume is well developed in the lowermost mantle as a broad hot region enriched in basaltic component, provided that the lithosphere is mechanically strong enough to inhibit spontaneous initiation of subduction by its own weight and that the internal heating rate is sufficiently high. Hot narrow plumes frequently rise up from the superplume to induce deep magma generation and hot spot magmatism, which in turn frequently induces new plate margins. The frequent plate margin formation keeps the activity of plate tectonics rather steady. The thermal and chemical state of the mantle remains rather steady, too. As the internal heating rate becomes lower, however, the narrow plumes from superplume become sporadic and significantly colder, deep magma generation becomes rare; and new plate margin formation becomes less frequent. As a consequence, the activity of plate tectonics and the thermal and chemical state of the mantle become fluctuating much with time. The mantle structure and plume behavior modeled here match with many observations for those of the Earth from the Archean to the present.