Flux melting

Definition

Flux melting is the process by which the addition of fluids or volatiles, such as water or carbon dioxide, lowers the melting temperature of rocks, allowing them to melt at relatively lower temperatures than they would under normal conditions. This phenomenon is crucial in subduction zones where an oceanic plate descends into the mantle, bringing water with it, which triggers melting in the overlying mantle wedge, resulting in volcanic activity.

5 Must Know Facts For Your Next Test

1. In subduction zones, the descending oceanic plate carries water into the mantle, which promotes flux melting in the overlying mantle wedge.
2. Flux melting can significantly increase magma production in subduction zones, contributing to the formation of arc volcanism.
3. The presence of volatiles can lead to more explosive volcanic eruptions due to the increased gas content in the generated magma.
4. Flux melting is essential for understanding the geochemical evolution of volcanic arcs and associated magma compositions.
5. This process is also important for recycling elements from the oceanic crust back into the mantle, influencing global geochemical cycles.

Review Questions

• How does flux melting contribute to magma generation in subduction zones?
  • Flux melting contributes to magma generation in subduction zones by introducing fluids from the descending oceanic plate into the overlying mantle. These fluids lower the melting temperature of rocks in the mantle wedge, allowing for melting to occur at lower temperatures. This process leads to increased magma production, which can result in volcanic activity and formation of volcanic arcs above the subduction zone.
• Discuss the role of water as a volatile in flux melting and its impact on volcanic eruptions.
  • Water acts as a crucial volatile in flux melting by significantly lowering the melting point of rocks. When water is introduced into the mantle wedge during subduction, it facilitates melting and increases magma generation. This increase in magma can lead to more explosive volcanic eruptions since the dissolved gases within the magma can expand rapidly as pressure decreases when it reaches the surface, resulting in violent outbursts.
• Evaluate how flux melting influences geochemical processes and element recycling within the Earth.
  • Flux melting plays a key role in geochemical processes by enabling the recycling of elements from oceanic crust back into the mantle. As oceanic plates subduct and introduce water and other volatiles into the mantle wedge, flux melting occurs, allowing for chemical interactions that alter magma compositions. This not only impacts volcanic activity but also affects global geochemical cycles by facilitating the movement of essential elements like carbon and nitrogen between different reservoirs within Earth’s systems.

Related terms

Subduction Zone: A subduction zone is a region where one tectonic plate moves under another and sinks into the mantle, often leading to volcanic activity and earthquake generation.

Magma Generation: Magma generation is the process through which molten rock is formed from solid rock due to various factors including temperature increase, pressure decrease, or the introduction of volatiles.

Mantle Wedge: The mantle wedge is the region of the Earth's mantle located above a subducting tectonic plate, where flux melting commonly occurs due to the introduction of water and other volatiles.