Which mechanism causes regional metamorphism of sedimentary rocks along a subduction zone?

💡 Explanation

When a tectonic plate subducts, the mantle generates magma, increasing the regional geothermal gradient via magma intrusion into the overlying crust, causing large-scale metamorphism of sedimentary rocks. Therefore, increased thermal gradient is the right answer, rather than rebound, infiltration or shear stress, which are caused by other mechanisms.

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