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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >On the anatomy of mantle plumes: effect of the viscosity ratio on entrainment and stirring
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On the anatomy of mantle plumes: effect of the viscosity ratio on entrainment and stirring

机译：关于地幔柱的解剖：粘度比对夹带和搅拌的​​影响

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摘要

Laminar entrainment of starting plumes with compositional buoyancy has been explored in a series of laboratory experiments. Two types of starting plume have been identified within the range of viscosity ratio ε_(as) of 10.4-856 (defined as the ratio of the ambient to the buoyant fluid). The first type represent a vortex ring at small viscosity ratio (ε_(as) < 11) in which the plumes entrain the ambient fluids and form a rotating multi-layered structure within their heads. This is similar to the well-known structure observed in the thermal starting plumes of fluids having a strong temperature-dependent viscosity. In contrast, the second type of starting plume represents a more chaotic stirring regime at higher viscosity ratio (104 < ε_(as) < 856). Here, in the the earlier stages, the plume head forms a double-layered structure by entrainment, with the buoyant fluid as the upper layer and the entrained fluid as the lower one. Thereafter, viscous coupling at the interface between the layers produces an intermediate stirring layer. This stirring layer grows with time with the end result that all fluids in the plume head mingle together. Using the fact that the resulting internal structure of the plume head depends on the viscosity ratio ε_(as) (a layered structure preserving the initial compositions vs. chaotic stirring tending towards homogeneity) a new viewpoint of mantle plume dynamics can be derived which is particularly useful in the interpretation of both spatial and temporal variations of geochemical data obtained from mantle plume products.
机译：在一系列的实验室实验中，已探索了带有成分浮力的初始羽流的层状夹带。在粘度比ε_（as）为10.4-856（定义为环境与浮力的比值）的范围内，已识别出两种类型的起始羽流。第一种类型代表小粘度比（ε_（as）<11）的涡流环，其中的羽流夹带环境流体并在其头部内形成旋转的多层结构。这类似于在具有强的温度依赖性粘度的流体的热启动羽流中观察到的众所周知的结构。相反，第二种类型的起始羽流在较高的粘度比（104 <ε_（as）<856）下表现出更加混乱的搅拌状态。在此，在较早的阶段中，羽状头部通过夹带形成双层结构，其中浮力流体作为上层，而夹带流体作为下层。此后，在层之间的界面处的粘性偶合产生中间搅拌层。该搅拌层随时间增长，最终结果是羽流头中的所有流体混合在一起。利用羽状头部的最终内部结构取决于粘度比ε_（as）（保留初始成分的层状结构与趋于均匀的混沌搅拌的事实）这一事实，可以得出地幔羽动力学的新观点，特别是可用于解释从地幔柱产品获得的地球化学数据的时空变化。

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