Magmatic differentiation

Definition

Magmatic differentiation is the process by which different minerals crystallize from magma at different temperatures and compositions, leading to the formation of a variety of igneous rocks. This process plays a crucial role in influencing the chemical composition and physical properties of the resulting rocks and minerals. As magma cools, variations in temperature and pressure cause specific minerals to crystallize, which can affect the magnetic properties of these materials significantly.

5 Must Know Facts For Your Next Test

1. Magmatic differentiation often results in the formation of both mafic (rich in magnesium and iron) and felsic (rich in silica) rocks, depending on the composition of the initial magma.
2. The magnetic properties of rocks can vary significantly based on the mineral composition resulting from magmatic differentiation, particularly with minerals like magnetite and hematite.
3. This process can also lead to the concentration of valuable minerals, such as copper and gold, as certain elements are segregated during crystallization.
4. The study of magmatic differentiation helps geologists understand volcanic activity and the evolution of magma chambers beneath the Earth's surface.
5. Different tectonic settings influence magmatic differentiation, affecting how quickly magma rises and cools, ultimately altering the types of rocks formed.

Review Questions

• How does fractional crystallization relate to magmatic differentiation and influence the mineral composition of igneous rocks?
  • Fractional crystallization is a key mechanism within magmatic differentiation that involves minerals crystallizing at different temperatures as magma cools. As these minerals form, they are removed from the melt, changing its composition over time. This process can lead to a diversity of igneous rock types with varying mineral content, such as basalt and granite, which directly influences their physical and magnetic properties.
• Discuss how thermal gradients impact magmatic differentiation and the types of rocks formed as a result.
  • Thermal gradients play a significant role in determining how quickly magma cools within the Earth's crust. A steep thermal gradient can result in rapid cooling, causing minerals to crystallize quickly and form fine-grained igneous rocks like basalt. Conversely, a gentle thermal gradient allows for slower cooling, leading to coarse-grained rocks like granite. These variations in cooling rates influence both mineral diversity and magnetic properties within differentiated magmas.
• Evaluate how magmatic differentiation can lead to economic benefits through the concentration of valuable minerals during volcanic activity.
  • Magmatic differentiation not only contributes to rock formation but also has significant economic implications due to its role in concentrating valuable minerals. During this process, certain elements become concentrated in specific mineral phases as they crystallize out of the melt. This can lead to economically important deposits of metals like copper, gold, and platinum group elements within igneous systems. Understanding this process enables geologists to target exploration efforts more effectively for these resources.

Related terms

Fractional Crystallization: A process that occurs during magmatic differentiation where minerals crystallize from cooling magma and are removed from the liquid, altering the composition of the remaining melt.

Magma Mixing: The process by which two different magmas with distinct compositions combine, resulting in a new magma that can lead to diverse mineral formation during differentiation.

Thermal Gradient: The variation in temperature with depth in the Earth's crust, which affects the rate of cooling of magma and thus influences the crystallization sequence of minerals.