Granulite facies

Definition

Granulite facies is a high-grade metamorphic environment characterized by the presence of specific minerals and textures that form under conditions of elevated temperature and pressure. In this setting, rocks often exhibit a well-defined foliation and are typically rich in quartz and feldspar, indicating significant metamorphic recrystallization. Understanding granulite facies helps connect mineral associations to the conditions of metamorphism and the resulting mineralogical compositions.

5 Must Know Facts For Your Next Test

1. Granulite facies typically forms at temperatures between 600°C to 800°C and pressures ranging from 4 to 12 kbar.
2. Common minerals found in granulite facies include feldspar, quartz, garnet, and sometimes pyroxene, reflecting the high-temperature conditions.
3. Rocks formed under granulite facies conditions are usually devoid of water, leading to anhydrous mineral compositions.
4. Granulite facies is often associated with continental collision zones, where tectonic forces elevate temperature and pressure conditions.
5. The study of granulite facies helps geologists understand the tectonic history and metamorphic evolution of a region.

Review Questions

• How do the mineral associations in granulite facies reflect the metamorphic conditions experienced by the rocks?
  • The mineral associations in granulite facies, such as quartz, feldspar, and garnet, reflect the high temperatures and pressures that these rocks have undergone during metamorphism. The presence of these minerals indicates significant recrystallization processes driven by intense heat, while their stability at such conditions shows that they are characteristic of high-grade metamorphism. Analyzing these associations allows geologists to infer the specific environmental conditions that contributed to the formation of granulite facies.
• Discuss the implications of granulite facies for understanding regional metamorphic processes in tectonically active areas.
  • Granulite facies provides vital information about regional metamorphic processes in tectonically active regions, especially where continental collisions occur. The formation of these high-grade metamorphic rocks indicates significant tectonic forces at play, which can influence local geology and topography. Additionally, studying granulite facies helps scientists interpret the thermal history of a region and understand how continental crust evolves under extreme conditions.
• Evaluate the significance of granulite facies within the broader context of understanding Earth's geological history and tectonic activity.
  • Granulite facies plays a crucial role in understanding Earth's geological history and tectonic activity because it reflects the extreme conditions under which continental crust undergoes metamorphism. By studying granulite facies, researchers can reconstruct past tectonic events, such as orogeny and rifting, as well as assess how these processes have shaped current landscapes. This evaluation contributes to a greater understanding of plate tectonics and the dynamic nature of Earth’s lithosphere over geological time.

Related terms

Metamorphism:

The process by which rocks undergo transformation due to changes in temperature, pressure, and chemically active fluids.

Foliation:

The repetitive layering in metamorphic rocks caused by the alignment of platy minerals under directed pressure.

Mineral Assemblage: A group of minerals that occur together in a rock and provide insight into the conditions of formation and metamorphic processes.