Mafic rock tend to be lower in silica but in iron and magnesium oxides. which rock is most mafic ? explain?

Question

1. rhyolite

2.andesite

3. basalt

Answer 1

Basalt is the most mafic, it has the highest concentration of Fe and Mg oxides in it. This is because of something called Bowen's reaction series, in which, due to magmatic differentiation, mafic minerals crystallise out first at higher temperatures. If the rock has no chance to cool sufficiently for acidic minerals to form, or cooling is rapid (such as in tholeiitic basalt), then there will be a high concentration of mafic minerals