Bowen's Reaction Series explains how minerals crystallize at different temperatures as magma cools. In the case of plagioclase feldspar, the chemical composition differs between basaltic and granitic rocks:
1. Plagioclase feldspar in basaltic rocks (like basalt) typically has a higher calcium (Ca) content compared to plagioclase feldspar in granitic rocks (like granite).
2. The plagioclase feldspar found in granitic rocks tends to have a higher sodium (Na) content relative to the plagioclase feldspar in basaltic rocks.
3. This difference in chemical composition is due to the cooling process of magma. Plagioclase feldspar crystallizes at different temperatures depending on the rock type. Basaltic rocks cool relatively quickly, leading to the formation of plagioclase feldspar with higher calcium content. On the other hand, granitic rocks cool more slowly, allowing plagioclase feldspar with higher sodium content to form.
In summary, the chemical composition of plagioclase feldspar in basaltic rock differs from that in granitic rock primarily in terms of calcium and sodium content, influenced by the cooling rates during the formation of the rocks.
