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尽管在400km和650km深度附近的地震不整合主要是由于相变，但在均一的地幔中它们却不一定是平衡相的界面。400km附近地震波速的跳跃很小以致不是在橄榄石或者橄榄-斜方辉石类为主的地幔岩中相变的结果。如果这是一个平衡相的界面，那么实际上就一定存在橄榄石和斜方辉石少于典型的地幔二辉橄榄岩或橄榄岩。可供选择的方案是：浅部地幔富橄榄石，而过渡带具较多的榴辉质，并具高的单斜辉石与石榴石的比率。富含橄榄石的物质例如方辉橄榄岩相对于其它的地幔组分具有浮力，其在地幔分异的各种作用期间可以聚集在浅部地幔中。过渡带中的地震波速小于被计算出的橄榄石、β-或γ-尖晶石高压相的波速，因此，过渡带贫橄榄石，其含量常小于50％。下地幔特征和“球粒陨石”地球（Earth）特征相一致，且和橄榄岩相比具有高的FeO或SiO2含量。所以,有证据表明，浅部地幔、过渡带和下地幔在成分、内在密度和相变深度上都有区别。为了验证这种可能性，提出浅部地幔（小于400km）是“表圈”（perisphere）的观点，表圈也可以称为橄榄岩壳。过渡带，或者中圈（mesoshpere）出现石榴石岩，主要是石榴石和镁铁榴石。在地球物理和地球化学方面．还没有证据可以证明在中圈和下地幔之间存在任何物质的相互交换，尽管有可能它?
Although the seismic unconformity near the depths of 400 km and 650 km is mainly due to phase transitions, they are not necessarily equilibrium phase interfaces in a homogeneous mantle. The jump in seismic velocity near 400 km is so small that it is not the result of phase transitions in olivine or olivine-orthopyroxene mantle rocks. If this is a balanced phase interface, there must actually be less olivine and orthopyroxene than typical mantle lherzolites or peridotites. Alternatives are: Oligospermiferous olivine, while transitional zone has more eclogite and has a high ratio of clinopyroxene to garnet. Olivine-rich materials, such as Hsp, have buoyancy relative to other mantle components that can accumulate in shallow mantle during various effects of mantle differentiation. The seismic velocity in the transition zone is less than the calculated velocity of the olivine, β-or γ-spinel high-pressure phase. Therefore, the transition zone is poorly olivine, and its content is often less than 50%. The lower mantle features are consistent with the Earth’s chondrites and have a high FeO or SiO2 content compared to peridotites. Therefore, there is evidence that the shallow mantle, transitional zone and lower mantle differ in composition, internal density and phase transformation depth. To test this possibility, a shallow mantle (less than 400 km) is proposed as a “perisphere,” and the bezel can also be called a peridotite. Transition zones, or mesoshpere, appear garnet rock, mainly garnet and magnesia. In geophysics and geochemistry. There is no evidence to prove that there is any exchange of matter between the middle and lower mantle, though it is possible?