Gabbro

Definition

Gabbro is a dark-colored, coarse-grained igneous rock that primarily consists of plagioclase feldspar and pyroxene. It forms when magma cools slowly beneath the Earth's surface, resulting in large crystals that are visible to the naked eye. This rock is a key component in understanding the processes of igneous rock formation and classification, as it represents a type of intrusive igneous rock that crystallizes from basaltic magma.

5 Must Know Facts For Your Next Test

1. Gabbro is chemically equivalent to basalt but differs in texture due to its slower cooling process beneath the surface.
2. This rock is often found in large bodies called plutons, which can form mountain ranges over millions of years.
3. Gabbro can contain minerals such as olivine and amphibole, adding to its variety and complexity.
4. It plays an important role in the Earth's crust, providing insight into the processes that shape oceanic crust and continental geology.
5. Due to its durability, gabbro is often used as a dimension stone in construction and landscaping.

Review Questions

• How does gabbro's formation process differ from that of basalt, and what implications does this have for their respective textures?
  • Gabbro forms when magma cools slowly beneath the Earth's surface, allowing large crystals to develop, while basalt forms from rapid cooling of lava at the surface, resulting in a fine-grained texture. This difference in cooling rates directly impacts their textures; gabbro has a coarse-grained texture with visible crystals, whereas basalt is fine-grained and typically lacks visible crystals. Understanding these differences helps geologists classify rocks based on their formation processes and mineral content.
• Discuss the significance of gabbro in understanding the geological processes occurring within the Earth's crust.
  • Gabbro is significant because it provides insights into the formation of the Earth's crust and the processes associated with magma intrusions. As an intrusive igneous rock, gabbro indicates that magma has solidified slowly underground, allowing scientists to study the conditions under which it formed. Additionally, by examining gabbro's mineral composition, geologists can learn about the types of magma present in different geological settings and how these contribute to broader tectonic activities.
• Evaluate the role of gabbro as a resource in construction and how its properties make it suitable for such applications.
  • Gabbro serves as an important resource in construction due to its hardness and durability, making it an ideal material for use as dimension stone in buildings and monuments. Its coarse texture allows for effective polishing and finishing, which enhances its aesthetic appeal for architectural designs. The presence of minerals like plagioclase feldspar gives gabbro unique coloration options that can complement various design choices. As a result, gabbro not only contributes to structural integrity but also adds visual value to construction projects.

Related terms

Basalt: A fine-grained igneous rock that forms from the rapid cooling of lava at the Earth's surface, often associated with volcanic activity.

Intrusive Igneous Rock: Igneous rocks that form from the cooling and solidification of magma beneath the Earth's surface, characterized by large crystals.

Plagioclase Feldspar: A group of tectosilicate minerals within the feldspar family, which are common constituents of gabbro and many other igneous rocks.