Which metamorphism occurs when rocks are altered by proximity to magma?

Which metamorphism occurs when rocks are altered by proximity to magma?

• A. Regional metamorphism
• B. Contact metamorphism
• C. Dynamic metamorphism
• D. Hydrothermal metamorphism

Answer: (B)

When rocks are heated by an intrusion of magma, their minerals recrystallize and form new mineral arrangements in response to the high temperature, with relatively low pressure. This localized heating creates a surrounding zone around the intrusion called a contact metamorphic aureole. The result is typically finer-grained, sometimes non-foliated rocks, reflecting metamorphism driven by heat from the magma itself. The other types involve large-scale pressure (regional metamorphism), deformation along faults (dynamic metamorphism), or chemical alteration by hot fluids (hydrothermal metamorphism), but the defining idea here is alteration caused by proximity to magma—contact metamorphism.

When rocks are heated by an intrusion of magma, their minerals recrystallize and form new mineral arrangements in response to the high temperature, with relatively low pressure. This localized heating creates a surrounding zone around the intrusion called a contact metamorphic aureole. The result is typically finer-grained, sometimes non-foliated rocks, reflecting metamorphism driven by heat from the magma itself. The other types involve large-scale pressure (regional metamorphism), deformation along faults (dynamic metamorphism), or chemical alteration by hot fluids (hydrothermal metamorphism), but the defining idea here is alteration caused by proximity to magma—contact metamorphism.