Solidification Of magma
Just as rocks partially melt to form different liquid compositions, magmas may solidify to different minerals at different times to form different solids (rocks). This process also results in the continuous change in the composition of the magma—if one mineral is removed the resulting composition is different. If this occurs, a new magma composition results.
The removal of crystals from the melt system may occur by several processes, including the squeezing of melt away from the crystals or by the sinking of dense crystals to the bottom of a magma chamber. These processes lead to magmatic differentiation by fractional crystallization, as first described by Norman Levi Bowen. Bowen systematically documented how crystallization of the first minerals changes the composition of the magma, and results in the formation of progressively more silicic rocks with decreasing temperature.
See also continental crust; convergent plate margin processes; divergent plate margin processes; petrology and petrography; volcano.
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