Fractional Crystallization

Definition

Fractional crystallization is the process by which different minerals crystallize from a cooling magma at different temperatures, leading to the separation of various components based on their chemical composition and melting points. This process significantly influences the composition of magma as it evolves, affecting everything from its physical properties to the types of volcanic products that eventually form.

5 Must Know Facts For Your Next Test

1. Fractional crystallization allows for the formation of diverse igneous rock types by separating heavier minerals that crystallize first from the remaining liquid magma.
2. This process can lead to a gradual change in magma composition, making it more silica-rich over time as lighter minerals are removed.
3. The order of mineral crystallization follows Bowen's Reaction Series, where ferromagnesian minerals crystallize at higher temperatures compared to felsic minerals.
4. Fractional crystallization is crucial in understanding volcanic activity, as it helps explain variations in magma composition found in different volcanic systems.
5. The dynamics of magma chambers are significantly influenced by fractional crystallization, impacting how magmas evolve before erupting.

Review Questions

• How does fractional crystallization contribute to the diversity of igneous rocks formed from a single magma source?
  • Fractional crystallization leads to the formation of diverse igneous rocks by allowing different minerals to crystallize at various temperatures as magma cools. This results in the separation of heavier minerals that crystallize first, changing the overall composition of the remaining liquid. As these processes continue, they can create rocks with varying textures and chemical compositions, demonstrating how one source of magma can yield multiple rock types through this mechanism.
• Discuss the implications of fractional crystallization on the physical properties of magma and how this affects volcanic eruptions.
  • Fractional crystallization alters the physical properties of magma by influencing its viscosity and gas content. As lighter, more silica-rich minerals form and settle out, the remaining liquid becomes less dense and more viscous. This change can affect how gases are dissolved within the magma, ultimately impacting eruption dynamics such as explosivity and the style of volcanic activity, where more viscous magmas tend to lead to more explosive eruptions.
• Evaluate how fractional crystallization interacts with tectonic processes to influence magma composition at convergent plate boundaries.
  • At convergent plate boundaries, fractional crystallization interacts with tectonic processes by modifying the initial composition of subducted material as it melts and rises. As the melt ascends and undergoes fractional crystallization, it can evolve into a more evolved, silica-rich composition that is characteristic of many volcanic arcs. This interaction not only shapes the physical characteristics of eruptions but also contributes to a better understanding of the tectonic settings that produce specific volcanic products.

Related terms

Bowen's Reaction Series:

A conceptual model that explains the sequence of mineral crystallization from cooling magma, illustrating how different minerals form at specific temperatures.

Magma Differentiation: The process by which magma changes composition as it cools and crystallizes, often resulting in the formation of distinct rock types.

Igneous Rocks: Rocks that form from the cooling and solidification of magma or lava, which can be classified into different types based on their mineral composition and texture.