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最近,提出了一种新的地幔对流模型,它与过去的标准模型相比要更接近实际一些。当然该模型还存在一些有争议的问题,不过我们认为,该模型可以调和不同研究领域矛盾的证据,因而为进一步研究对流提供一种新的构架。借助于我们最近的一些研究工作(Albarede,1998)以及其他人的一些研究工作,我们对由Kellogg等(1999)、van der Hilst和Karason(1999)提出的模型作了更深入的研究。新的观点认为,一个深地层大致位于地幔中较低的第三层,该地层的化学成分明显地与其上覆的地层不同。这样的一个深地层将决定地球放热元素的实际部分,并有助于达到一些临界同位素体系的热平衡。化学变化和热密度变化间微妙的平衡产生了明显的动态地形,这一过程使得地震波监测复杂化,但却有利于沉降板块的穿过。热柱将形成于对流地幔的地层边界与上覆部分的过渡带中。若割裂气体消失、气体不完全消失或气体逸出的地层与从地震学角度已被证实的、被660km间断面分开的上下地幔之间的关系,要协调其他矛盾的证据看来还要颇费一番功夫。
Recently, a new model of mantle convection was proposed, which is closer to actual than the standard model in the past. Of course, there are still some controversial issues with the model, but we think the model can reconcile the evidence of contradictions in different research fields and thus provide a new framework for further research on convection. With the help of some of our recent work (Albarede, 1998) and others, we have conducted a more in-depth study of the model proposed by Kellogg et al. (1999), van der Hilst and Karason (1999). The new view is that a deep layer is generally located in the lower third layer of the mantle, the chemical composition of the formation is obviously different from the overlying strata. Such a deep formation will determine the actual portion of the Earth’s exothermic element and help to achieve thermal equilibrium of some of the critical isotope systems. The delicate balance between chemical and heat density changes produces a clear dynamic topography that complicates seismic monitoring but facilitates the passage of subsidence plates. Hot pillars will form in the transition zone between the boundary and overburden of the convective mantle. It would seem to be quite expensive to reconcile the evidence of other contradictions if the disappearing gas, gas disappearing completely, or the gas escaping from the strata and the seismologically proven relationship between the upper and lower mantle separated by the 660 km interval A lot of effort.