地幔的成分估计相当于超镁铁质岩(表1),因此,我们转向调查出露于地表的超镁铁质岩。超镁铁质岩有可能直接来自地幔,也有可能是来自地幔派生产物——如玄武岩浆。岩石学问题就是要确定代表地幔物质的岩石(如果有的话),以及演译那种导致地幔物质侵位至地壳中的作用。 The composition of the mantle is estimated to be equivalent to that of ultramafic rocks (Table 1), so we turned to the investigation of ultramafic rocks exposed to the surface. It is possible that the ultramafic rocks come directly from the mantle or from mantle-derived products such as basalt magma. The petrology problem is to determine the rocks, if any, that represent the material of the mantle, and to interpret the effects that cause mantle material to invade into the earth’s crust.