The volatiles and fluids released from the subducted organic-rich sediments reduce the oxygen fugacity of the mantle wedge, leading to the production of more reduced magmas. These reduced magmas are typically characterized by higher concentrations of ferrous iron (Fe2+) and lower concentrations of ferric iron (Fe3+). This change in the iron oxidation state can have a number of effects on the composition and properties of the resulting magmas, including:
- *Increased magma fluidity*: Reduced magmas are generally more fluid than oxidized magmas, which can affect their emplacement style and eruptive behavior.
- *Lower magma viscosity*: Reduced magmas have lower viscosities than oxidized magmas, making them easier to transport and erupt.
- *Greater potential for explosive eruptions*: Reduced magmas can produce more explosive eruptions than oxidized magmas due to the higher gas content and lower viscosity of the reduced magmas.
In addition to these direct effects, changes in oxygen fugacity can also have indirect effects on convergent margin magmatism by influencing the composition and mineralogy of the mantle wedge. For example, reduced conditions can lead to the formation of more hydrous minerals in the mantle wedge, which can further reduce the melting temperature of the mantle and promote magma production.
The magnitude of the effects of OAEs on convergent margin magmatism depends on a number of factors, including the規模of the OAE, the amount of organic-rich material that is subducted, and the composition of the mantle wedge. However, OAEs can have a significant impact on the oxygen fugacity and composition of convergent margin magmas, and can play an important role in the evolution of convergent margin magmatic systems.
