Last Minerals

Definition

Last minerals are the final minerals to crystallize from a cooling magma, typically forming at lower temperatures and higher pressures. They represent the end stage of the crystallization sequence in Bowen's Reaction Series, showcasing how different minerals emerge from magma as it cools and evolves, which also ties into magmatic differentiation processes that influence the composition of igneous rocks.

5 Must Know Facts For Your Next Test

1. Last minerals include quartz, muscovite, and potassium feldspar, which typically crystallize after earlier-forming minerals like olivine and pyroxene.
2. The formation of last minerals indicates a significant change in the chemical environment of the magma as it cools, leading to a higher concentration of certain elements like silica.
3. Understanding last minerals helps geologists predict the mineralogy of igneous rocks and their behavior during cooling and solidification.
4. Last minerals often contribute to the development of pegmatites, which are coarse-grained igneous rocks rich in rare elements.
5. The presence and types of last minerals in an igneous rock can provide insights into the history of the magma chamber and its evolutionary processes.

Review Questions

• How do last minerals illustrate the principles of Bowen's Reaction Series?
  • Last minerals exemplify the principles of Bowen's Reaction Series by showcasing how mineral crystallization occurs in a systematic sequence as magma cools. They crystallize at lower temperatures and are influenced by earlier formed minerals, demonstrating how different environmental conditions affect mineral formation. This series not only highlights which minerals crystallize first but also emphasizes the significance of last minerals in completing the process.
• Discuss how fractional crystallization impacts the composition of last minerals found in igneous rocks.
  • Fractional crystallization significantly influences the composition of last minerals found in igneous rocks by altering the chemical makeup of the remaining melt as certain minerals solidify first. As early-forming minerals are removed from the melt, elements like silicon become more concentrated, leading to the formation of last minerals such as quartz and potassium feldspar. This process plays a crucial role in determining not just mineral content but also affects overall rock properties.
• Evaluate the significance of last minerals in understanding geological processes related to magmatic differentiation.
  • Last minerals are key to understanding geological processes linked to magmatic differentiation because they reflect the changing conditions within a magma chamber during its evolution. By studying these minerals, geologists can infer how factors like temperature, pressure, and elemental concentration shift over time. This evaluation provides insights into the formation and characteristics of igneous rocks, helping to unravel complex geological histories and processes that shape Earth's crust.

Related terms

Bowen's Reaction Series: A conceptual model that illustrates the sequence of mineral crystallization from cooling magma, showing how minerals form at different temperatures.

Fractional Crystallization: A process where different minerals crystallize out of a cooling magma at different temperatures, affecting the remaining melt composition.

Igneous Rocks: Rocks formed from the solidification of molten magma or lava, with composition influenced by the minerals present during crystallization.