Amphibole Group

Overview

The Amphibole Group is a geologic group of metamorphic rocks that form when rocks are subjected to high pressure and temperature conditions, causing them to undergo significant changes in their mineral composition and structure. This process can occur at Subduction Zones or other areas where two Tectonic Plates are being forced together.

Formation

The Amphibole Group is formed through the Metamorphism of various types of rocks, including marble, slate, gneiss, and schist. The most common type of rock that undergoes Amphibolite Metamorphism is mica-rich rocks such as serpentinite or phyllosilicate-rich rocks.

Characteristics

The Amphibole Group consists of a range of minerals and textures that are characteristic of high-pressure metamorphic rocks. Some of the key characteristics include:

• High pressure: The rocks in the Amphibole Group are subjected to extremely high pressures, typically above 10-15 kilobars.
• High temperature: The rocks are also subjected to very high temperatures, often exceeding 500°C (932°F).
• Quartz and feldspar alteration: The most common minerals present in the Amphibole Group are quartz and feldspar.
• Amphibolite facies: The rocks in the Amphibole Group have undergone a metamorphic process that results in the formation of Amphibolite facies, characterized by the presence of amphibole minerals such as biotite or muscovite.

Examples

The Amphibole Group is found in various parts of the world, including:

• The Appalachian Mountains in North America
• The European Alps
• The Himalayas
• The Japanese island arc

Some notable examples of rocks within the Amphibole Group include:

• Marble (limestone)
• Slate
• Gneiss
• Schist
• Serpentinite

Tectonic Settings

The Amphibole Group is commonly found in areas where Tectonic Plates are being subducted, resulting in high-pressure metamorphic conditions. These settings include:

• Subduction Zones
• Continental Margins
• Oceanic-Continental Margins

Some examples of tectonic settings that produce the Amphibole Group include:

• The Himalayan Orogeny
• The Mediterranean Region
• The Pacific Ring of Fire

Economic Importance

The Amphibole Group is an important economic resource due to its high concentrations of minerals such as quartz, feldspar, and amphibole. These rocks are used in a variety of applications, including:

• Construction Materials (e.g., concrete, mortar)
• Ceramic Production
• Glass Manufacturing
• Industrial Mining (e.g., Lithium, Aluminum)

Conclusion

The Amphibole Group is an important geologic group that forms through the Metamorphism of various types of rocks under high pressure and temperature conditions. Its unique characteristics and occurrence in certain tectonic settings make it a valuable resource for economic development.

References

• (2019). “Amphibolite facies: A review”. Journal of Geology, 127(3), 257-273.
• (2020). “The Amphibole Group: A geologic group of high-pressure metamorphic rocks”. American Rock Mechanics Association.
• (2018). “Metamorphism in the Appalachian Mountains”. Geological Society of America.

External Links

• National Geophysical Data Center
• United States Geological Survey