Which statement best describes the crystallization of magmas?
A)Early formed crystals are big and irregular in shape, but gradually get smaller and have better developed faces with time as they react with the residual melt.
B)A felsic magma produces only one rock type equal to the melt composition by crystallizing quartz, feldspar, and ferromagnesian minerals in fixed proportions and compositions until all of the melt is used up.
C)During crystallization, which can occur over an interval of about 200° C, the composition of the residual melt continuously changes as particular ions are selectively removed and incorporated into certain minerals that crystallize early at high temperature.
D)Like the freezing of water, cooling magmas hit their crystallization temperature and stop cooling until all the melt has crystallized, whereupon cooling resumes.

Question

Quizplus · Accepted Answer

During the crystallization of magmas, the composition of the residual melt continuously changes as certain ions are selectively removed and incorporated into minerals that crystallize early at high temperature. This process can occur over a range of temperatures, and the residual melt's composition may change continuously. The statement that early formed crystals gradually become smaller and have better-developed faces with time is accurate but not the best description of crystallization overall. Felsic magmas do indeed produce rock types based on specific compositions, but this statement is not comprehensive enough to capture the whole process of crystallization. Finally, the statement that cooling magmas stop at their crystallization temperature and resume cooling only after all the melt has crystallized oversimplifies the process.

Which Statement Best Describes the Crystallization of Magmas