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文中由蛇绿岩和蛇绿岩上覆岩系的差别，引出上部洋壳和下部洋壳的概念。指出下部洋壳和上部洋壳有许多不同之处：首先它们的组成不同，下部洋壳仅由镁铁超镁铁岩组成，包括玄武岩、辉长岩、超镁铁质堆晶岩等；而上部洋壳则由沉积岩（主要是深海相的，少量为浅海相）和长英质、镁铁质以及超镁铁的喷出岩（及少量侵入岩）组成。其次洋壳岩浆的成因和形成方式不同，下洋壳产于板块扩张脊，是板块扩张作用的产物；上洋壳产于扩张轴外，属于轴外岩浆系列。当洋盆闭合洋壳侵位到陆壳之上时，下洋壳即成为蛇绿岩，而上洋壳则构成蛇绿岩的上覆岩系。
In this paper, the difference between overlying strata of ophiolite and ophiolite leads to the concept of upper and lower oceanic crust. It is pointed out that there are many differences between the lower and upper oceanic crusts: firstly, their composition is different; the lower crust consists of mafic ultramafic rocks, including basalt, gabbro, ultramafic hematite, etc. The upper oceanic crust consists of sedimentary rocks (mainly deep-sea facies, small amounts of shallow marine facies) and extrusive rocks (with small amounts of intrusive rocks) of felsic, mafic and ultramafic rocks. Secondly, the genesis and formation of the oceanic crust magma are different. The oceanic crust is produced on the plate expansion ridge and is the product of plate expansion. The oceanic crust is produced outside the expansion axis and belongs to the off-axis magmatic series. When the oceanic crust is emplaced over the continental crust, the oceanic crust becomes an ophiolite, while the upper oceanic crust constitutes an overlying rock series of ophiolite.