How and why the plagioclase feldspar in basaltic rocks differs from that in grantic rocks

Both are different because of their Silica content and the rates of cooling.

Explanation:

Plagioclase feldspar is igneous rocks. This group rocks are forming from minerals. They are very major to the dominant minerals in igneous rocks which present on the earth's crust. Rhyolite, andesite, basalt, diorite and granite are the extrusive and intrusive igneous salts where plagioclase is the major constituents. Igneous rocks are the rocks which formed due to the crystallisation of magma. The main difference between granite and basalt is that one their silica content and second their rates of cooling. A granite contains 73%SiO2 and basalt contains 53% SiO2. Both are slowly cooled inside the earth's crust.