Quartz typically forms through two main processes during magmatic differentiation:
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Crystallization from Silicate Melt: As magma cools, various minerals crystallize at different temperatures. Quartz typically crystallizes later in the process, as it is one of the last minerals to form from a silicate melt due to its high silica content and lower melting point compared to other minerals. This process is a part of fractional crystallization, where different minerals crystallize out of the melt, changing the composition of the remaining liquid.
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Partial Melting and Fractional Crystallization: During the evolution of the magma, partial melting of previous rocks can lead to an increase in silica content in the residual melt. As this melt undergoes fractional crystallization, certain minerals crystallize and settle out, leaving the composition richer in silica. This enriched melt can eventually crystallize into quartz.
Overall, quartz primarily forms through these two processes in the context of magmatic differentiation, reflecting its stability and silica dominance in the melt evolution.