Discontinuous series

Definition

A discontinuous series refers to a specific sequence of mineral crystallization that occurs during the cooling of magma, where different minerals crystallize at different temperatures and do not form a continuous progression. This concept is crucial in understanding how igneous rocks develop and how minerals behave under varying thermal conditions. In this series, certain minerals are formed in a stepwise manner rather than transitioning smoothly from one to the next.

5 Must Know Facts For Your Next Test

1. The discontinuous series primarily involves minerals like olivine, pyroxene, amphibole, and biotite, each crystallizing at progressively lower temperatures.
2. As temperature decreases, minerals in the discontinuous series are replaced by more stable phases, leading to a diverse mineral assemblage in igneous rocks.
3. In contrast to the continuous series, where plagioclase feldspar varies in composition, the discontinuous series exhibits distinct mineral identities with specific crystallization temperatures.
4. Understanding discontinuous series helps geologists predict mineral assemblages found in different types of igneous rocks based on their formation conditions.
5. The concept of discontinuous series emphasizes the importance of temperature in determining which minerals can coexist in an igneous rock.

Review Questions

• How does the discontinuous series relate to Bowen's Reaction Series and what implications does this have for mineral crystallization?
  • The discontinuous series is a key component of Bowen's Reaction Series, illustrating how certain minerals crystallize at distinct temperature intervals during magma cooling. This relationship shows that minerals like olivine and pyroxene form first at high temperatures, while others such as amphibole and biotite appear as the temperature drops. This understanding aids in predicting mineral compositions in igneous rocks and illustrates how temperature affects mineral stability and formation.
• Discuss the differences between the discontinuous series and the continuous series in terms of mineral composition and crystallization processes.
  • The main difference between the discontinuous series and continuous series lies in their crystallization behavior. The discontinuous series consists of distinct minerals forming at specific temperature ranges, such as olivine transitioning to pyroxene as conditions change. In contrast, the continuous series represents a gradual change in composition among plagioclase feldspars without a distinct change in mineral type. This difference highlights how various factors influence mineral development during magma cooling.
• Evaluate the significance of understanding discontinuous series in interpreting geological history and rock formation processes.
  • Grasping the concept of discontinuous series is vital for interpreting geological history as it provides insights into past volcanic activity and magma evolution. By analyzing which minerals formed under specific temperature conditions, geologists can reconstruct the thermal history of igneous bodies. This knowledge helps in understanding not only mineral assemblages but also broader geological processes such as tectonics and magmatic differentiation, ultimately shaping our comprehension of Earth's evolution.

Related terms

Bowen's Reaction Series:

A model that describes the order in which minerals crystallize from cooling magma, illustrating both the discontinuous and continuous series of mineral formation.

Fractional Crystallization: A process by which different minerals crystallize out of magma at different temperatures, altering the composition of the remaining liquid.

Igneous Rocks:

Rocks formed through the cooling and solidification of magma or lava, encompassing a wide variety of textures and compositions based on their formation history.