Lava erupting earlier would come from the top of the magma chamber, and lava erupting later would come from lower down.
This left branch is called a discontinuous reaction series because each mineral has a different crystalline structure.
Recall that olivine is composed of a single tetrahedra and that the other minerals in this sequence are composed of single chains, double chains, and sheet structures, respectively.
Evidence of this type led them to look into the possibility that a single magma might produce rocks of varying mineral content. Bowen discovered that as magma cools in the laboratory, certain minerals crystallize first.
A pioneering investigation into the crystallization of magma was carried out by N. At successively lower temperature, other minerals begin to crystallize as shown in Figure 3.6.
But at the same time, it will be enriched in the elements contained in the later forming minerals, namely sodium and potassium.
Further, the silicon content of the melt becomes enriched toward the latter stages of crystallization.On the upper left branch of this reaction series, olivine, the first mineral to form, Ml] react with the remaining melt to become pyroxene.This reaction will continue until the last mineral in the series, biotite mica, is formed.Such a large variety of igneous rocks exists that it is logical to assume an equally large variety of magmas must also exist.However, geologists have found that various eruptive stages of the same volcano often extrude lavas exhibiting somewhat different mineral compositions, particularly if an extensive period of time separated the eruptions.Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger.