Final answer:
Leucosomes are lighter-colored portions in migmatite and are primarily composed of low melting point minerals, predominantly quartz, which is rich in silica.
Step-by-step explanation:
The term leucosome refers to the lighter-colored portions of a migmatite, which is a type of rock formed during high-grade metamorphism that involves partial melting. Leucosomes are composed mainly of minerals that have lower melting points and are typically rich in silica and feldspar.
Therefore, the answer to the question would be e. quartz, as quartz is a major mineral component of leucosome due to its high silica content, commonly associated with feldspar in the formation of these lighter-colored bands in migmatite. Other minerals like spinel, olivine, biotite, garnet, cordierite, and hornblende are not as common in leucosomes as quartz.