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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 >Geochemical observations and one layer mantle convection
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Geochemical observations and one layer mantle convection

机译：地球化学观测和一层地幔对流

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Rare gas systematics are at the heart of the discrepancy between geophysical and geochemical models. Since more and more robust evidence of whole mantle convection comes from seismic tomography and geoid modeling, the interpretation of high ~3He/~4He in some oceanic island basalts as being primitive has to be revisited. A time dependent model with five reservoirs (bulk mantle, continental crust, atmosphere, residual deep mantle and D") is studies for Rb/Sr and U/Pb/He systems. The dynamics of this model correspond to whole mantle convection in which subducted oceanic crust, transformed into dense assemblages, partially segregates to form a D" layer growing with time as in Christensen and Hofmann [J. Geophys. Res. 99 (1994) 19867-19884]. A complementary cold and depleted harzburgitic lithosphere remains above D". We assume that hotspots arise from the deep thermal boundary layer and tap, in variable proportions, material from both the residual deep mantle and D". The difference between HIUM and Hawaiian basalts is attributed to HIMU being mostly from strongly degassed oceanic crust, though enriched in incompatibles (D"), while Hawaii is mostly from MORB source residuals that are variably degassed and depleted. We suggest that a significant part of the Earth's radioactive elements (approx 1/3) is trapped in the D" layer.
机译：稀有气体系统是地球物理模型与地球化学模型之间差异的核心。由于越来越多有力的证据证明整个地幔对流来自地震层析成像和大地水准面模型，因此必须重新考虑在某些海洋岛玄武岩中对〜3He /〜4He的解释是原始的。对于Rb / Sr和U / Pb / He系统，研究了一个具有五个储集层（大块地幔，大陆壳，大气，残余深地幔和D”）的时变模型。该模型的动力学对应于俯冲作用下的整个地幔对流像克里斯滕森和霍夫曼一样，随着时间的推移，大洋地壳被转变成致密的集合体，部分地分离成一个D”层[J．地理学。 Res。 99（1994）19867-19884]。补充的冷的和枯竭的哈茨堡性岩石圈仍保持在D“以上。我们假设热点来自深部热边界层，并以可变的比例从剩余的深地幔和D”中挖掘物质。 HIUM和夏威夷玄武岩之间的差异是由于HIMU主要来自强烈脱气的洋壳，尽管富含不相容物质（D“），而夏威夷则主要来自MORB来源的残余物，这些残余物不同程度地被脱气和耗尽。我们建议地球的放射性元素（约1/3）被困在D“层中。

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