Crystal Fractionation

Definition

Crystal fractionation is the process where different minerals crystallize from a magma at different temperatures and compositions, leading to changes in the composition of the remaining liquid. This process plays a crucial role in the differentiation of planetary bodies, as it can lead to the formation of various igneous rocks and contribute to the overall chemical evolution of a planet's crust and mantle. By altering the composition of the magma as minerals crystallize, crystal fractionation helps explain the diversity of rock types observed on different planetary surfaces.

5 Must Know Facts For Your Next Test

1. Crystal fractionation is influenced by temperature and pressure conditions during the cooling of magma, affecting which minerals crystallize first.
2. The process can lead to the creation of layered igneous bodies, where different layers represent variations in mineral composition resulting from fractional crystallization.
3. Elements with different affinities for specific minerals will concentrate in certain phases during crystallization, impacting the geochemical characteristics of the remaining melt.
4. As magma rises through the crust, it can undergo crystal fractionation, resulting in more evolved magmas that produce different rock types as they cool.
5. Crystal fractionation is a key factor in the differentiation of planets and can affect tectonic activity, volcanic processes, and overall planetary geology.

Review Questions

• How does crystal fractionation contribute to the diversity of igneous rocks found on planetary surfaces?
  • Crystal fractionation contributes to the diversity of igneous rocks by altering the composition of magma as it cools. Different minerals crystallize at varying temperatures, which means that as certain minerals form and settle out, the remaining liquid becomes enriched in other elements. This results in a variety of rock types that reflect these compositional changes, showing how a single source of magma can lead to multiple distinct igneous rocks.
• Discuss the relationship between crystal fractionation and magma differentiation in terms of planetary geological processes.
  • Crystal fractionation is a critical mechanism in magma differentiation, where the initial composition of magma evolves as certain minerals crystallize. As crystals form and are removed from the melt, they change its chemical makeup, leading to differences in viscosity and eruptive behavior. This process can result in a range of geological features such as layered intrusions and diverse volcanic rocks, illustrating how crystal fractionation drives geological evolution on planets.
• Evaluate how understanding crystal fractionation enhances our knowledge of planetary formation and evolution.
  • Understanding crystal fractionation enhances our knowledge of planetary formation by providing insights into how planetary bodies differentiate over time. By studying how different minerals crystallize from molten rock under varying conditions, scientists can infer past geological processes that shaped a planet's crust and mantle. This information helps reconstruct a planet's thermal history, volcanic activity, and even its potential for hosting life by revealing how its materials evolved chemically and physically throughout its history.

Related terms

Magma Differentiation: The process by which different types of rocks form from a common magma due to variations in temperature, pressure, and composition.

Fractional Crystallization:

A specific type of crystal fractionation where solid crystals are removed from the liquid melt, thus changing the composition of the remaining liquid.

Geochemical Evolution: The changes in chemical composition and mineralogy of planetary materials over time, influenced by processes like crystallization and metamorphism.