Magma Generation at a Convergent Margin

Title: Magma Generation at a Convergent Margin
Description: Magma generation at a convergent margin is a complex process. As the oceanic plate subducts beneath the Pacific Plate, the slab dewaters, lowering the melting temperature of the mantle between the Benioff Zone and the overriding plate. Here, a melt begins to form. As continental crust is light and buoyant, this melt has trouble rising. Therefore, very few primitive magmas will erupt at the surface at these settings. As the magma rises, several important processes occur. First, fractional crystallization and differentiation occur as the melt slowly cools underground. Assimilation occurs as the hot melt heats the surrounding country rock. Other processes, such as stoping, likely also occur. Some of the magma is unable to reach the surface and is trapped beneath the crust. Here, it cools and adds to the continental plate; a phenomena known as crustal underplating.
Subject: Petrology 2015 Final Project: Convergent Margin (Cascade Arc)
Creator: Devon Gorbey
Source: John D. Winter, "Principles of Igneous and Metamorphic Petrology
Mediator: Tamara Carley